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Fukumoto K, Lee S, Adachi SI, Suzuki Y, Kusakabe K, Yamamoto R, Kitatani M, Ishida K, Nakagawa Y, Merkel M, Shiga D, Kumigashira H. Surface terminations control charge transfer from bulk to surface states in topological insulators. Sci Rep 2024; 14:10537. [PMID: 38719934 PMCID: PMC11079079 DOI: 10.1038/s41598-024-61172-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2024] [Accepted: 05/02/2024] [Indexed: 05/12/2024] Open
Abstract
Topological insulators (TI) hold significant potential for various electronic and optoelectronic devices that rely on the Dirac surface state (DSS), including spintronic and thermoelectric devices, as well as terahertz detectors. The behavior of electrons within the DSS plays a pivotal role in the performance of such devices. It is expected that DSS appear on a surface of three dimensional(3D) TI by mechanical exfoliation. However, it is not always the case that the surface terminating atomic configuration and corresponding band structures are homogeneous. In order to investigate the impact of surface terminating atomic configurations on electron dynamics, we meticulously examined the electron dynamics at the exfoliated surface of a crystalline 3D TI (Bi2 Se3 ) with time, space, and energy resolutions. Based on our comprehensive band structure calculations, we found that on one of the Se-terminated surfaces, DSS is located within the bulk band gap, with no other surface states manifesting within this region. On this particular surface, photoexcited electrons within the conduction band effectively relax towards DSS and tend to linger at the Dirac point for extended periods of time. It is worth emphasizing that these distinct characteristics of DSS are exclusively observed on this particular surface.
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Affiliation(s)
- Keiki Fukumoto
- High energy accelerator research organization (KEK), 1-1 Oho, Tsukuba, Ibaraki, 305-0801, Japan.
| | - Seunghee Lee
- High energy accelerator research organization (KEK), 1-1 Oho, Tsukuba, Ibaraki, 305-0801, Japan
| | - Shin-Ichi Adachi
- High energy accelerator research organization (KEK), 1-1 Oho, Tsukuba, Ibaraki, 305-0801, Japan
| | - Yuta Suzuki
- The Graduate University for Advanced Studies (SOKENDAI), Hayama, Kanagawa, 240-0193, Japan
| | - Koichi Kusakabe
- University of Hyogo, 3-2-1 Kouto, Kamigori-cho, Ako-gun, Hyogo, 678-1297, Japan
| | - Rikuto Yamamoto
- University of Hyogo, 3-2-1 Kouto, Kamigori-cho, Ako-gun, Hyogo, 678-1297, Japan
| | - Motoharu Kitatani
- University of Hyogo, 3-2-1 Kouto, Kamigori-cho, Ako-gun, Hyogo, 678-1297, Japan
| | - Kunio Ishida
- Utsunomiya University, 7-1-2 Yoto, Utsunomiya, Tochigi, 321-8585, Japan
| | | | - Michael Merkel
- FOCUS GmbH, Neukirchner Str.2, 65510, Huenstetten, Germany
| | - Daisuke Shiga
- Tohoku University, Katahira 2-1-1, Aoba-ku, Sendai, Miyagi, 980-8577, Japan
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2
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He X, Kimura S, Katase T, Tadano T, Matsuishi S, Minohara M, Hiramatsu H, Kumigashira H, Hosono H, Kamiya T. Inverse-Perovskite Ba 3 BO (B = Si and Ge) as a High Performance Environmentally Benign Thermoelectric Material with Low Lattice Thermal Conductivity. Adv Sci (Weinh) 2024; 11:e2307058. [PMID: 38145354 PMCID: PMC10933667 DOI: 10.1002/advs.202307058] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/25/2023] [Revised: 11/19/2023] [Indexed: 12/26/2023]
Abstract
High energy-conversion efficiency (ZT) of thermoelectric materials has been achieved in heavy metal chalcogenides, but the use of toxic Pb or Te is an obstacle for wide applications of thermoelectricity. Here, high ZT is demonstrated in toxic-element free Ba3 BO (B = Si and Ge) with inverse-perovskite structure. The negatively charged B ion contributes to hole transport with long carrier life time, and their highly dispersive bands with multiple valley degeneracy realize both high p-type electronic conductivity and high Seebeck coefficient, resulting in high power factor (PF). In addition, extremely low lattice thermal conductivities (κlat ) 1.0-0.4 W m-1 K-1 at T = 300-600 K are observed in Ba3 BO. Highly distorted O-Ba6 octahedral framework with weak ionic bonds between Ba with large mass and O provides low phonon velocities and strong phonon scattering in Ba3 BO. As a consequence of high PF and low κlat , Ba3 SiO (Ba3 GeO) exhibits rather high ZT = 0.16-0.84 (0.35-0.65) at T = 300-623 K (300-523 K). Finally, based on first-principles carrier and phonon transport calculations, maximum ZT is predicted to be 2.14 for Ba3 SiO and 1.21 for Ba3 GeO at T = 600 K by optimizing hole concentration. Present results propose that inverse-perovskites would be a new platform of environmentally-benign high-ZT thermoelectric materials.
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Affiliation(s)
- Xinyi He
- MDX Research Center for Element StrategyInternational Research Frontiers InitiativeTokyo Institute of Technology4259 Nagatsuta, MidoriYokohama226‐8501Japan
| | - Shigeru Kimura
- MDX Research Center for Element StrategyInternational Research Frontiers InitiativeTokyo Institute of Technology4259 Nagatsuta, MidoriYokohama226‐8501Japan
| | - Takayoshi Katase
- MDX Research Center for Element StrategyInternational Research Frontiers InitiativeTokyo Institute of Technology4259 Nagatsuta, MidoriYokohama226‐8501Japan
| | - Terumasa Tadano
- Research Center for Magnetic and Spintronic MaterialsNational Institute for Materials Science1‐2‐1 SengenTsukubaIbaraki305‐0047Japan
| | - Satoru Matsuishi
- MDX Research Center for Element StrategyInternational Research Frontiers InitiativeTokyo Institute of Technology4259 Nagatsuta, MidoriYokohama226‐8501Japan
- Research Center for Materials NanoarchitectonicsNational Institute for Materials Science1‐1 NamikiTsukuba, Ibaraki305‐0044Japan
| | - Makoto Minohara
- Research Institute for Advanced Electronics and PhotonicsNational Institute of Advanced Industrial Science and TechnologyTsukubaIbaraki305‐8568Japan
| | - Hidenori Hiramatsu
- MDX Research Center for Element StrategyInternational Research Frontiers InitiativeTokyo Institute of Technology4259 Nagatsuta, MidoriYokohama226‐8501Japan
- Laboratory for Materials and StructuresInstitute of Innovative Research, Tokyo Institute of Technology4259 NagatsutaMidori, Yokohama226‐8501Japan
| | - Hiroshi Kumigashira
- Institute of Multidisciplinary Research for Advanced MaterialsTohoku UniversitySendai980‐8577Japan
| | - Hideo Hosono
- MDX Research Center for Element StrategyInternational Research Frontiers InitiativeTokyo Institute of Technology4259 Nagatsuta, MidoriYokohama226‐8501Japan
- Research Center for Materials NanoarchitectonicsNational Institute for Materials Science1‐1 NamikiTsukuba, Ibaraki305‐0044Japan
| | - Toshio Kamiya
- MDX Research Center for Element StrategyInternational Research Frontiers InitiativeTokyo Institute of Technology4259 Nagatsuta, MidoriYokohama226‐8501Japan
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3
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Nakamura T, Sugihara H, Chen Y, Yukawa R, Ohtsubo Y, Tanaka K, Kitamura M, Kumigashira H, Kimura SI. Two-dimensional heavy fermion in a monoatomic-layer Kondo lattice YbCu 2. Nat Commun 2023; 14:7850. [PMID: 38040781 PMCID: PMC10692116 DOI: 10.1038/s41467-023-43662-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2023] [Accepted: 11/16/2023] [Indexed: 12/03/2023] Open
Abstract
The Kondo effect between localized f-electrons and conductive carriers leads to exotic physical phenomena. Among them, heavy-fermion (HF) systems, in which massive effective carriers appear due to the Kondo effect, have fascinated many researchers. Dimensionality is also an important characteristic of the HF system, especially because it is strongly related to quantum criticality. However, the realization of the perfect two-dimensional (2D) HF materials is still a challenging topic. Here, we report the surface electronic structure of the monoatomic-layer Kondo lattice YbCu2 on a Cu(111) surface observed by synchrotron-based angle-resolved photoemission spectroscopy. The 2D conducting band and the Yb 4f state, located very close to the Fermi level, are observed. These bands are hybridized at low-temperature, forming the 2D HF state, with an evaluated coherence temperature of about 30 K. The effective mass of the 2D state is enhanced by a factor of 100 by the development of the HF state. Furthermore, clear evidence of the hybridization gap formation in the temperature dependence of the Kondo-resonance peak has been observed below the coherence temperature. Our study provides a new candidate as an ideal 2D HF material for understanding the Kondo effect at low dimensions.
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Affiliation(s)
- Takuto Nakamura
- Graduate School of Frontier Biosciences, Osaka University, Suita, 565-0871, Japan.
- Department of Physics, Graduate School of Science, Osaka University, Toyonaka, 560-0043, Japan.
| | - Hiroki Sugihara
- Department of Physics, Graduate School of Science, Osaka University, Toyonaka, 560-0043, Japan
| | - Yitong Chen
- Department of Physics, Graduate School of Science, Osaka University, Toyonaka, 560-0043, Japan
| | - Ryu Yukawa
- Graduate School of Engineering, Osaka University, Suita, 565-0871, Japan
| | - Yoshiyuki Ohtsubo
- National Institutes for Quantum Science and Technology, Sendai, 980-8579, Japan
| | | | - Miho Kitamura
- Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba, 305-0801, Japan
| | - Hiroshi Kumigashira
- Institute of Multidisciplinary Research for Advanced Materials (IMRAM), Tohoku University, Sendai, 980-8577, Japan
| | - Shin-Ichi Kimura
- Graduate School of Frontier Biosciences, Osaka University, Suita, 565-0871, Japan.
- Department of Physics, Graduate School of Science, Osaka University, Toyonaka, 560-0043, Japan.
- Institute for Molecular Science, Okazaki, 444-8585, Japan.
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4
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Honma A, Takane D, Souma S, Yamauchi K, Wang Y, Nakayama K, Sugawara K, Kitamura M, Horiba K, Kumigashira H, Tanaka K, Kim TK, Cacho C, Oguchi T, Takahashi T, Ando Y, Sato T. Antiferromagnetic topological insulator with selectively gapped Dirac cones. Nat Commun 2023; 14:7396. [PMID: 37978297 PMCID: PMC10656484 DOI: 10.1038/s41467-023-42782-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2023] [Accepted: 10/20/2023] [Indexed: 11/19/2023] Open
Abstract
Antiferromagnetic (AF) topological materials offer a fertile ground to explore a variety of quantum phenomena such as axion magnetoelectric dynamics and chiral Majorana fermions. To realize such intriguing states, it is essential to establish a direct link between electronic states and topology in the AF phase, whereas this has been challenging because of the lack of a suitable materials platform. Here we report the experimental realization of the AF topological-insulator phase in NdBi. By using micro-focused angle-resolved photoemission spectroscopy, we discovered contrasting surface electronic states for two types of AF domains; the surface having the out-of-plane component in the AF-ordering vector displays Dirac-cone states with a gigantic energy gap, whereas the surface parallel to the AF-ordering vector hosts gapless Dirac states despite the time-reversal-symmetry breaking. The present results establish an essential role of combined symmetry to protect massless Dirac fermions under the presence of AF order and widen opportunities to realize exotic phenomena utilizing AF topological materials.
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Affiliation(s)
- A Honma
- Department of Physics, Graduate School of Science, Tohoku University, Sendai, 980-8578, Japan
| | - D Takane
- Department of Physics, Graduate School of Science, Tohoku University, Sendai, 980-8578, Japan
| | - S Souma
- Center for Science and Innovation in Spintronics (CSIS), Tohoku University, Sendai, 980-8577, Japan.
- Advanced Institute for Materials Research (WPI-AIMR), Tohoku University, Sendai, 980-8577, Japan.
| | - K Yamauchi
- Center for Spintronics Research Network (CSRN), Osaka University, Toyonaka, Osaka, 560-8531, Japan
| | - Y Wang
- Institute of Physics II, University of Cologne, Köln, 50937, Germany
| | - K Nakayama
- Department of Physics, Graduate School of Science, Tohoku University, Sendai, 980-8578, Japan
- Precursory Research for Embryonic Science and Technology (PRESTO), Japan Science and Technology Agency (JST), Tokyo, 102-0076, Japan
| | - K Sugawara
- Department of Physics, Graduate School of Science, Tohoku University, Sendai, 980-8578, Japan
- Advanced Institute for Materials Research (WPI-AIMR), Tohoku University, Sendai, 980-8577, Japan
| | - M Kitamura
- Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki, 305-0801, Japan
- National Institutes for Quantum Science and Technology (QST), Sendai, 980-8579, Japan
| | - K Horiba
- National Institutes for Quantum Science and Technology (QST), Sendai, 980-8579, Japan
| | - H Kumigashira
- Institute of Multidisciplinary Research for Advanced Materials (IMRAM), Tohoku University, Sendai, 980-8577, Japan
| | - K Tanaka
- UVSOR Synchrotron Facility, Institute for Molecular Science, Okazaki, 444-8585, Japan
| | - T K Kim
- Diamond Light Source, Harwell Science and Innovation Campus, Didcot, Oxfordshire, OX11 0QX, UK
| | - C Cacho
- Diamond Light Source, Harwell Science and Innovation Campus, Didcot, Oxfordshire, OX11 0QX, UK
| | - T Oguchi
- Center for Spintronics Research Network (CSRN), Osaka University, Toyonaka, Osaka, 560-8531, Japan
| | - T Takahashi
- Department of Physics, Graduate School of Science, Tohoku University, Sendai, 980-8578, Japan
- Advanced Institute for Materials Research (WPI-AIMR), Tohoku University, Sendai, 980-8577, Japan
| | - Yoichi Ando
- Institute of Physics II, University of Cologne, Köln, 50937, Germany
| | - T Sato
- Department of Physics, Graduate School of Science, Tohoku University, Sendai, 980-8578, Japan.
- Center for Science and Innovation in Spintronics (CSIS), Tohoku University, Sendai, 980-8577, Japan.
- Advanced Institute for Materials Research (WPI-AIMR), Tohoku University, Sendai, 980-8577, Japan.
- International Center for Synchrotron Radiation Innov1ation Smart (SRIS), Tohoku University, Sendai, 980-8577, Japan.
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5
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Namba M, Takatsu H, Mikita R, Sijia Y, Murayama K, Li HB, Terada R, Tassel C, Ubukata H, Ochi M, Saez-Puche R, Latasa EP, Ishimatsu N, Shiga D, Kumigashira H, Kinjo K, Kitagawa S, Ishida K, Terashima T, Fujita K, Mashiko T, Yanagisawa K, Kimoto K, Kageyama H. Large Perpendicular Magnetic Anisotropy Induced by an Intersite Charge Transfer in Strained EuVO 2H Films. J Am Chem Soc 2023; 145:21807-21816. [PMID: 37770040 DOI: 10.1021/jacs.3c04521] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/03/2023]
Abstract
Perovskite oxides ABO3 continue to be a major focus in materials science. Of particular interest is the interplay between A and B cations as exemplified by intersite charge transfer (ICT), which causes novel phenomena including negative thermal expansion and metal-insulator transition. However, the ICT properties were achieved and optimized by cationic substitution or ordering. Here we demonstrate an anionic approach to induce ICT using an oxyhydride perovskite, EuVO2H, which has alternating layers of EuH and VO2. A bulk EuVO2H behaves as a ferromagnetic insulator with a relatively high transition temperature (TC) of 10 K. However, the application of external pressure to the EuIIVIIIO2H bulk or compressive strain from the substrate in the thin films induces ICT from the EuIIH layer to the VIIIO2 layer due to the extended empty V dxy orbital. The ICT phenomenon causes the VO2 layer to become conductive, leading to an increase in TC that is dependent on the number of carriers in the dxy orbitals (up to a factor of 4 for 10 nm thin films). In addition, a large perpendicular magnetic anisotropy appears with the ICT for the films of <100 nm, which is unprecedented in materials with orbital-free Eu2+, opening new perspectives for applications. The present results provide opportunities for the acquisition of novel functions by alternating transition metal/rare earth layers with heteroanions.
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Affiliation(s)
- Morito Namba
- Department of Energy and Hydrocarbon Chemistry, Graduate School of Engineering, Kyoto University, Kyoto 615-8510, Japan
| | - Hiroshi Takatsu
- Department of Energy and Hydrocarbon Chemistry, Graduate School of Engineering, Kyoto University, Kyoto 615-8510, Japan
| | - Riho Mikita
- Department of Energy and Hydrocarbon Chemistry, Graduate School of Engineering, Kyoto University, Kyoto 615-8510, Japan
| | - Yao Sijia
- Department of Energy and Hydrocarbon Chemistry, Graduate School of Engineering, Kyoto University, Kyoto 615-8510, Japan
| | - Kantaro Murayama
- Department of Energy and Hydrocarbon Chemistry, Graduate School of Engineering, Kyoto University, Kyoto 615-8510, Japan
| | - Hao-Bo Li
- Department of Energy and Hydrocarbon Chemistry, Graduate School of Engineering, Kyoto University, Kyoto 615-8510, Japan
| | - Ryo Terada
- Department of Energy and Hydrocarbon Chemistry, Graduate School of Engineering, Kyoto University, Kyoto 615-8510, Japan
| | - Cédric Tassel
- Department of Energy and Hydrocarbon Chemistry, Graduate School of Engineering, Kyoto University, Kyoto 615-8510, Japan
| | - Hiroki Ubukata
- Department of Energy and Hydrocarbon Chemistry, Graduate School of Engineering, Kyoto University, Kyoto 615-8510, Japan
| | - Masayuki Ochi
- Department of Physics, Osaka University, Machikaneyama-cho, Toyonaka, Osaka 560-0043, Japan
- Forefront Research Center, Osaka University, Machikaneyama-cho, Toyonaka, Osaka 560-0043, Japan
| | - Regino Saez-Puche
- Departamento Química Inorgánica, Facultad de Ciencias Químicas, Universidad Complutense de Madrid, Ciudad Universitaria, 28040, Madrid, Spain
| | - Elias Palacios Latasa
- INMA, CSIC-Universidad de Zaragoza, 50009, Zaragoza, Spain
- Departamento de Ciencia y Tecnología de Materiales y Fluidos, Universidad de Zaragoza, 50018, Zaragoza, Spain
| | - Naoki Ishimatsu
- Department of Physical Science, Graduate School of Science, Hiroshima University, Higashihiroshima, Hiroshima 739-8526, Japan
| | - Daisuke Shiga
- Department of Physics, Tohoku University, Sendai 980-8578, Japan
| | | | - Katsuki Kinjo
- Department of Physics, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
| | - Shunsaku Kitagawa
- Department of Physics, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
| | - Kenji Ishida
- Department of Physics, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
| | - Takahito Terashima
- Department of Physics, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
| | - Koji Fujita
- Department of Material Chemistry, Graduate School of Engineering, Kyoto University, Kyoto 615-8510, Japan
| | - Takeaki Mashiko
- National Institute for Materials Science, Ibaraki 305-0044, Japan
| | | | - Koji Kimoto
- National Institute for Materials Science, Ibaraki 305-0044, Japan
| | - Hiroshi Kageyama
- Department of Energy and Hydrocarbon Chemistry, Graduate School of Engineering, Kyoto University, Kyoto 615-8510, Japan
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6
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Fujiwara K, Kato Y, Abe H, Noguchi S, Shiogai J, Niwa Y, Kumigashira H, Motome Y, Tsukazaki A. Berry curvature contributions of kagome-lattice fragments in amorphous Fe-Sn thin films. Nat Commun 2023; 14:3399. [PMID: 37311774 DOI: 10.1038/s41467-023-39112-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2023] [Accepted: 05/25/2023] [Indexed: 06/15/2023] Open
Abstract
Amorphous semiconductors are widely applied to electronic and energy-conversion devices owing to their high performance and simple fabrication processes. The topological concept of the Berry curvature is generally ill-defined in amorphous solids, due to the absence of long-range crystalline order. Here, we demonstrate that the Berry curvature in the short-range crystalline order of kagome-lattice fragments effectively contributes to the anomalous electrical and magneto-thermoelectric properties in Fe-Sn amorphous films. The Fe-Sn films on glass substrates exhibit large anomalous Hall and Nernst effects comparable to those of the single crystals of topological semimetals Fe3Sn2 and Fe3Sn. With modelling, we reveal that the Berry curvature contribution in the amorphous state likely originates from randomly distributed kagome-lattice fragments. This microscopic interpretation sheds light on the topology of amorphous materials, which may lead to the realization of functional topological amorphous electronic devices.
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Affiliation(s)
- Kohei Fujiwara
- Institute for Materials Research, Tohoku University, Sendai, 980-8577, Japan.
| | - Yasuyuki Kato
- Department of Applied Physics, University of Tokyo, Tokyo, 113-8656, Japan
| | - Hitoshi Abe
- Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba, 305-0801, Japan
- Department of Materials Structure Science, SOKENDAI (Graduate University of Advanced Studies), Tsukuba, 305-0801, Japan
- Graduate School of Science and Engineering, Ibaraki University, Mito, 310-8512, Japan
| | - Shun Noguchi
- Institute for Materials Research, Tohoku University, Sendai, 980-8577, Japan
| | - Junichi Shiogai
- Institute for Materials Research, Tohoku University, Sendai, 980-8577, Japan
- Department of Physics, Osaka University, Toyonaka, 560-0043, Japan
| | - Yasuhiro Niwa
- Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba, 305-0801, Japan
- Department of Materials Structure Science, SOKENDAI (Graduate University of Advanced Studies), Tsukuba, 305-0801, Japan
| | - Hiroshi Kumigashira
- Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba, 305-0801, Japan
- Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai, 980-8577, Japan
| | - Yukitoshi Motome
- Department of Applied Physics, University of Tokyo, Tokyo, 113-8656, Japan
| | - Atsushi Tsukazaki
- Institute for Materials Research, Tohoku University, Sendai, 980-8577, Japan
- Center for Science and Innovation in Spintronics (CSIS), Core Research Cluster, Tohoku University, Sendai, 980-8577, Japan
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7
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Sugawara K, Kusaka H, Kawakami T, Yanagizawa K, Honma A, Souma S, Nakayama K, Miyakawa M, Taniguchi T, Kitamura M, Horiba K, Kumigashira H, Takahashi T, Orimo SI, Toyoda M, Saito S, Kondo T, Sato T. Direct Imaging of Band Structure for Powdered Rhombohedral Boron Monosulfide by Microfocused ARPES. Nano Lett 2023; 23:1673-1679. [PMID: 36849129 PMCID: PMC10000586 DOI: 10.1021/acs.nanolett.2c04048] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/17/2022] [Revised: 02/04/2023] [Indexed: 06/18/2023]
Abstract
Boron-based two-dimensional (2D) materials are an excellent platform for nanoelectronics applications. Rhombohedral boron monosulfide (r-BS) is attracting particular attention because of its unique layered crystal structure suitable for exploring various functional properties originating in the 2D nature. However, studies to elucidate its fundamental electronic states have been largely limited because only tiny powdered crystals were available, hindering a precise investigation by spectroscopy such as angle-resolved photoemission spectroscopy (ARPES). Here we report the direct mapping of the band structure with a tiny (∼20 × 20 μm2) r-BS powder crystal by utilizing microfocused ARPES. We found that r-BS is a p-type semiconductor with a band gap of >0.5 eV characterized by the anisotropic in-plane effective mass. The present results demonstrate the high applicability of micro-ARPES to tiny powder crystals and widen an opportunity to access the yet-unexplored electronic states of various novel materials.
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Affiliation(s)
- Katsuaki Sugawara
- Department
of Physics, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan
- Advanced Institute for Materials Research (WPI-AIMR), Center for Science and
Innovation in Spintronics, Institute of Multidisciplinary Research for Advanced
Materials (IMRAM), Institute for Material Research, and International Center for Synchrotron Radiation
Innovation Smart (SRIS), Tohoku University, Sendai 980-8577, Japan
- Precursory
Research for Embryonic Science and Technology (PRESTO), Japan Science and Technology Agency (JST), Tokyo 102-0076, Japan
| | - Haruki Kusaka
- Department
of Materials Science and Tsukuba Research Center for Energy Materials
Science (TREMS), Faculty of Pure and Applied Sciences, University of Tsukuba, Tsukuba 305-8573, Japan
| | - Tappei Kawakami
- Department
of Physics, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan
| | - Koki Yanagizawa
- Department
of Physics, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan
| | - Asuka Honma
- Department
of Physics, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan
| | - Seigo Souma
- Advanced Institute for Materials Research (WPI-AIMR), Center for Science and
Innovation in Spintronics, Institute of Multidisciplinary Research for Advanced
Materials (IMRAM), Institute for Material Research, and International Center for Synchrotron Radiation
Innovation Smart (SRIS), Tohoku University, Sendai 980-8577, Japan
| | - Kosuke Nakayama
- Department
of Physics, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan
| | - Masashi Miyakawa
- Research
Center for Functional Materials, National
Institute for Materials Science, Tsukuba 305-0044, Japan
| | - Takashi Taniguchi
- International
Center for Materials Nanoarchitectonics, National Institute for Materials Science, Tsukuba 305-0044, Japan
| | - Miho Kitamura
- Photon
Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba 305-0801, Japan
| | - Koji Horiba
- National
Institutes for Quantum Science and Technology (QST), Sendai 980-8579, Japan
| | - Hiroshi Kumigashira
- Advanced Institute for Materials Research (WPI-AIMR), Center for Science and
Innovation in Spintronics, Institute of Multidisciplinary Research for Advanced
Materials (IMRAM), Institute for Material Research, and International Center for Synchrotron Radiation
Innovation Smart (SRIS), Tohoku University, Sendai 980-8577, Japan
| | - Takashi Takahashi
- Department
of Physics, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan
| | - Shin-ichi Orimo
- Advanced Institute for Materials Research (WPI-AIMR), Center for Science and
Innovation in Spintronics, Institute of Multidisciplinary Research for Advanced
Materials (IMRAM), Institute for Material Research, and International Center for Synchrotron Radiation
Innovation Smart (SRIS), Tohoku University, Sendai 980-8577, Japan
| | - Masayuki Toyoda
- Department
of Physics, Tokyo Institute of Technology, Meguro-ku, Tokyo 152-8551, Japan
| | - Susumu Saito
- Department
of Physics, Tokyo Institute of Technology, Meguro-ku, Tokyo 152-8551, Japan
- Advanced
Research Center for Quantum Physics and Nanoscience, Tokyo Institute of Technology, Meguro-ku, Tokyo 152-8551, Japan
- Materials
Research Centre for Element Strategy, Tokyo
Institute of Technology, Yokohama 226-8503, Japan
| | - Takahiro Kondo
- Advanced Institute for Materials Research (WPI-AIMR), Center for Science and
Innovation in Spintronics, Institute of Multidisciplinary Research for Advanced
Materials (IMRAM), Institute for Material Research, and International Center for Synchrotron Radiation
Innovation Smart (SRIS), Tohoku University, Sendai 980-8577, Japan
- Department
of Materials Science and Tsukuba Research Center for Energy Materials
Science (TREMS), Faculty of Pure and Applied Sciences, University of Tsukuba, Tsukuba 305-8573, Japan
| | - Takafumi Sato
- Department
of Physics, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan
- Advanced Institute for Materials Research (WPI-AIMR), Center for Science and
Innovation in Spintronics, Institute of Multidisciplinary Research for Advanced
Materials (IMRAM), Institute for Material Research, and International Center for Synchrotron Radiation
Innovation Smart (SRIS), Tohoku University, Sendai 980-8577, Japan
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8
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Kato T, Li Y, Nakayama K, Wang Z, Souma S, Matsui F, Kitamura M, Horiba K, Kumigashira H, Takahashi T, Yao Y, Sato T. Fermiology and Origin of T_{c} Enhancement in a Kagome Superconductor Cs(V_{1-x}Nb_{x})_{3}Sb_{5}. Phys Rev Lett 2022; 129:206402. [PMID: 36461993 DOI: 10.1103/physrevlett.129.206402] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/09/2022] [Revised: 06/14/2022] [Accepted: 10/06/2022] [Indexed: 06/17/2023]
Abstract
Kagome metals AV_{3}Sb_{5} (A=K, Rb, and Cs) exhibit a characteristic superconducting ground state coexisting with a charge density wave (CDW), whereas the mechanisms of the superconductivity and CDW have yet to be clarified. Here we report a systematic angle-resolved photoemission spectroscopy (ARPES) study of Cs(V_{1-x}Nb_{x})_{3}Sb_{5} as a function of Nb content x, where isovalent Nb substitution causes an enhancement of superconducting transition temperature (T_{c}) and the reduction of CDW temperature (T_{CDW}). We found that the Nb substitution shifts the Sb-derived electron band at the Γ point downward and simultaneously moves the V-derived band around the M point upward to lift up the saddle point (SP) away from the Fermi level, leading to the reduction of the CDW-gap magnitude and T_{CDW}. This indicates a primary role of the SP density of states to stabilize the CDW. The present result also suggests that the enhancement of superconductivity by Nb substitution is caused by the cooperation between the expansion of the Sb-derived electron pocket and the recovery of the V-derived density of states at the Fermi level.
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Affiliation(s)
- Takemi Kato
- Department of Physics, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan
| | - Yongkai Li
- Centre for Quantum Physics, Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurement (MOE), School of Physics, Beijing Institute of Technology, Beijing 100081, People's Republic of China
- Beijing Key Lab of Nanophotonics and Ultrafine Optoelectronic Systems, Beijing Institute of Technology, Beijing 100081, People's Republic of China
- Material Science Center, Yangtze Delta Region Academy of Beijing Institute of Technology, Jiaxing 314011, People's Republic of China
| | - Kosuke Nakayama
- Department of Physics, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan
- Precursory Research for Embryonic Science and Technology (PRESTO), Japan Science and Technology Agency (JST), Tokyo 102-0076, Japan
| | - Zhiwei Wang
- Centre for Quantum Physics, Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurement (MOE), School of Physics, Beijing Institute of Technology, Beijing 100081, People's Republic of China
- Beijing Key Lab of Nanophotonics and Ultrafine Optoelectronic Systems, Beijing Institute of Technology, Beijing 100081, People's Republic of China
- Material Science Center, Yangtze Delta Region Academy of Beijing Institute of Technology, Jiaxing 314011, People's Republic of China
| | - Seigo Souma
- Center for Science and Innovation in Spintronics, Tohoku University, Sendai 980-8577, Japan
- Advanced Institute for Materials Research (WPI-AIMR), Tohoku University, Sendai 980-8577, Japan
| | - Fumihiko Matsui
- UVSOR Synchrotron Facility, Institute for Molecular Science, Okazaki 444-8585, Japan
| | - Miho Kitamura
- Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki 305-0801, Japan
| | - Koji Horiba
- Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki 305-0801, Japan
- National Institutes for Quantum Science and Technology (QST), Sendai 980-8579, Japan
| | - Hiroshi Kumigashira
- Institute of Multidisciplinary Research for Advanced Materials (IMRAM), Tohoku University, Sendai 980-8577, Japan
| | - Takashi Takahashi
- Department of Physics, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan
- Center for Science and Innovation in Spintronics, Tohoku University, Sendai 980-8577, Japan
- Advanced Institute for Materials Research (WPI-AIMR), Tohoku University, Sendai 980-8577, Japan
| | - Yugui Yao
- Centre for Quantum Physics, Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurement (MOE), School of Physics, Beijing Institute of Technology, Beijing 100081, People's Republic of China
- Beijing Key Lab of Nanophotonics and Ultrafine Optoelectronic Systems, Beijing Institute of Technology, Beijing 100081, People's Republic of China
| | - Takafumi Sato
- Department of Physics, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan
- Center for Science and Innovation in Spintronics, Tohoku University, Sendai 980-8577, Japan
- Advanced Institute for Materials Research (WPI-AIMR), Tohoku University, Sendai 980-8577, Japan
- International Center for Synchrotron Radiation Innovation Smart (SRIS), Tohoku University, Sendai 980-8577, Japan
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9
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Kaneta-Takada S, Kitamura M, Arai S, Arai T, Okano R, Anh LD, Endo T, Horiba K, Kumigashira H, Kobayashi M, Seki M, Tabata H, Tanaka M, Ohya S. Giant spin-to-charge conversion at an all-epitaxial single-crystal-oxide Rashba interface with a strongly correlated metal interlayer. Nat Commun 2022; 13:5631. [PMID: 36163469 PMCID: PMC9512910 DOI: 10.1038/s41467-022-33350-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2022] [Accepted: 09/12/2022] [Indexed: 11/30/2022] Open
Abstract
The two-dimensional electron gas (2DEG) formed at interfaces between SrTiO3 (STO) and other oxide insulating layers is promising for use in efficient spin-charge conversion due to the large Rashba spin-orbit interaction (RSOI). However, these insulating layers on STO prevent the propagation of a spin current injected from an adjacent ferromagnetic layer. Moreover, the mechanism of the spin-current flow in these insulating layers is still unexplored. Here, using a strongly correlated polar-metal LaTiO3+δ (LTO) interlayer and the 2DEG formed at the LTO/STO interface in an all-epitaxial heterostructure, we demonstrate giant spin-to-charge current conversion efficiencies, up to ~190 nm, using spin-pumping ferromagnetic-resonance voltage measurements. This value is the highest among those reported for all materials, including spin Hall systems. Our results suggest that the strong on-site Coulomb repulsion in LTO and the giant RSOI of LTO/STO may be the key to efficient spin-charge conversion with suppressed spin-flip scattering. Our findings highlight the hidden inherent possibilities of oxide interfaces for spin-orbitronics applications. The interface between perovskite-oxide SrTiO3 and other oxides realizes efficient spin-to-charge current conversion; however, the typically insulating oxides hinder the propagation of spin-currents. Here the authors achieve a record efficiency by replacing an oxide insulator with a strongly-correlated polar metal.
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Affiliation(s)
- Shingo Kaneta-Takada
- Department of Electrical Engineering and Information Systems, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan.
| | - Miho Kitamura
- Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba, Ibaraki, 305-0801, Japan
| | - Shoma Arai
- Department of Electrical Engineering and Information Systems, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan
| | - Takuma Arai
- Department of Electrical Engineering and Information Systems, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan
| | - Ryo Okano
- Department of Electrical Engineering and Information Systems, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan
| | - Le Duc Anh
- Department of Electrical Engineering and Information Systems, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan.,PRESTO, Japan Science and Technology Agency, 4-1-8 Honcho, Kawaguchi, Saitama, 332-0012, Japan
| | - Tatsuro Endo
- Department of Electrical Engineering and Information Systems, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan
| | - Koji Horiba
- Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba, Ibaraki, 305-0801, Japan
| | - Hiroshi Kumigashira
- Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba, Ibaraki, 305-0801, Japan.,Institute of Multidisciplinary Research for Advanced Materials (IMRAM), Tohoku University, Sendai, Miyagi, 980-8577, Japan
| | - Masaki Kobayashi
- Department of Electrical Engineering and Information Systems, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan.,Center for Spintronics Research Network (CSRN), The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan
| | - Munetoshi Seki
- Department of Electrical Engineering and Information Systems, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan.,Center for Spintronics Research Network (CSRN), The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan
| | - Hitoshi Tabata
- Department of Electrical Engineering and Information Systems, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan.,Center for Spintronics Research Network (CSRN), The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan
| | - Masaaki Tanaka
- Department of Electrical Engineering and Information Systems, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan. .,Center for Spintronics Research Network (CSRN), The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan.
| | - Shinobu Ohya
- Department of Electrical Engineering and Information Systems, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan. .,Center for Spintronics Research Network (CSRN), The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan.
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10
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He X, Chen J, Katase T, Minohara M, Ide K, Hiramatsu H, Kumigashira H, Hosono H, Kamiya T. High-Mobility Metastable Rock-Salt Type (Sn,Ca)Se Thin Film Stabilized by Direct Epitaxial Growth on a YSZ (111) Single-Crystal Substrate. ACS Appl Mater Interfaces 2022; 14:18682-18689. [PMID: 35420024 DOI: 10.1021/acsami.2c01464] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Metastable cubic (Sn1-xPbx)Se with x ≥ 0.5 is expected to be a high mobility semiconductor due to its Dirac-like electronic state, but it has an excessively high carrier concentration of ∼1019 cm-3 and is not suitable for semiconductor device applications such as thin film transistors and solar cells. Further, thin films of (Sn1-xPbx)Se require a complicated synthesis process because of the high vapor pressure of Pb. We herein report the direct growth of metastable cubic (Sn1-xCax)Se films alloyed with CaSe, which has a wider bandgap and lower vapor pressure than PbSe. The cubic (Sn1-xCax)Se epitaxial films with x = 0.4-0.8 are stabilized on YSZ (111) single crystalline substrates by pulsed laser deposition. (Sn1-xCax)Se has a direct-transition-type bandgap, and the bandgap energy can be varied from 1.4 eV (x = 0.4) to 2.0 eV (x = 0.8) by changing x. These films with x = 0.4-0.6 show p-type conduction with low hole carrier concentrations of ∼1017 cm-3. Hall mobility analysis suggests that the hole transport would be dominated by 180° rotational domain structures, which is specific to (111) oriented epitaxial films. However, it, in turn, clarifies that the in-grain carrier mobility in the (Sn0.6Ca0.4)Se film is as high as 322 cm2/(Vs), which is much higher than those in thermodynamically stable layered SnSe and other Sn-based layered semiconductor films at room temperature. Therefore, the present results prove the potential of high mobility (Sn1-xCax)Se films for semiconductor device applications via a simple thin-film deposition process.
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Affiliation(s)
- Xinyi He
- Laboratory for Materials and Structures, Institute of Innovative Research, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama, 226-8503, Japan
| | - Jinshuai Chen
- Laboratory for Materials and Structures, Institute of Innovative Research, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama, 226-8503, Japan
| | - Takayoshi Katase
- Laboratory for Materials and Structures, Institute of Innovative Research, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama, 226-8503, Japan
| | - Makoto Minohara
- Research Institute for Advanced Electronics and Photonics, National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki 305-8568, Japan
| | - Keisuke Ide
- Laboratory for Materials and Structures, Institute of Innovative Research, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama, 226-8503, Japan
| | - Hidenori Hiramatsu
- Laboratory for Materials and Structures, Institute of Innovative Research, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama, 226-8503, Japan
- Materials Research Center for Element Strategy, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama, 226-8503, Japan
| | - Hiroshi Kumigashira
- Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai 980-8577, Japan
| | - Hideo Hosono
- Materials Research Center for Element Strategy, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama, 226-8503, Japan
| | - Toshio Kamiya
- Laboratory for Materials and Structures, Institute of Innovative Research, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama, 226-8503, Japan
- Materials Research Center for Element Strategy, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama, 226-8503, Japan
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11
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Shiraishi A, Kimura S, He X, Watanabe N, Katase T, Ide K, Minohara M, Matsuzaki K, Hiramatsu H, Kumigashira H, Hosono H, Kamiya T. Design, Synthesis, and Optoelectronic Properties of the High-Purity Phase in Layered AETMN 2 ( AE = Sr, Ba; TM = Ti, Zr, Hf) Semiconductors. Inorg Chem 2022; 61:6650-6659. [PMID: 35442660 DOI: 10.1021/acs.inorgchem.2c00604] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We report the synthesis and optoelectronic properties of high phase-purity (>94 mol %) bulk polycrystals of KCoO2-type layered nitrides AETMN2 (AE = Sr, Ba; and TM = Ti, Zr, Hf), which are expected to exhibit unique electron transport properties originating from their natural two-dimensional (2D) electronic structure, but high-purity intrinsic samples have yet been reported. The bulks were synthesized using a solid-state reaction between AENH and TMN precursors with NaN3 to achieve high N chemical potential during the reaction. The AETMN2 bulks are n-type semiconductors with optical band gaps of 1.63 eV for SrTiN2, 1.97 eV for BaZrN2, and 2.17 eV for BaHfN2. SrTiN2 and BaZrN2 bulks show degenerated electron conduction due to the natural high-density electron doping and paramagnetic behavior in all of the temperature ranges examined, while such unintentional carrier generation is largely suppressed in BaHfN2, which exhibits nondegenerated electron conduction. The BaHfN2 sample also exhibits weak ferromagnetic behavior at temperatures lower than 35 K. Density functional theory calculations suggest that the high-density electron carriers in SrTiN2 come from oxygen impurity substitution at the N site (ON) acting as a shallow donor even if the high-N chemical potential synthesis conditions are employed. On the other hand, the formation energy of ON becomes larger in BaHfN2 because of the stronger TM-N chemical bonds. Present results demonstrate that the easiness of impurity incorporation is designed by density functional calculations to produce a more intrinsic semiconductor in wider chemical conditions, opening a way to cultivating novel functional materials that are sensitive to atmospheric impurities and defects.
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Affiliation(s)
- Akihiro Shiraishi
- Laboratory for Materials and Structures, Institute of Innovative Research, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama 226-8503, Japan
| | - Shigeru Kimura
- Laboratory for Materials and Structures, Institute of Innovative Research, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama 226-8503, Japan
| | - Xinyi He
- Laboratory for Materials and Structures, Institute of Innovative Research, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama 226-8503, Japan
| | - Naoto Watanabe
- Laboratory for Materials and Structures, Institute of Innovative Research, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama 226-8503, Japan
| | - Takayoshi Katase
- Laboratory for Materials and Structures, Institute of Innovative Research, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama 226-8503, Japan
| | - Keisuke Ide
- Laboratory for Materials and Structures, Institute of Innovative Research, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama 226-8503, Japan
| | - Makoto Minohara
- Research Institute for Advanced Electronics and Photonics, National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki 305-8568, Japan
| | - Kosuke Matsuzaki
- Materials Research Center for Element Strategy, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama 226-8503, Japan
| | - Hidenori Hiramatsu
- Laboratory for Materials and Structures, Institute of Innovative Research, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama 226-8503, Japan.,Materials Research Center for Element Strategy, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama 226-8503, Japan
| | - Hiroshi Kumigashira
- Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai 980-8577, Japan
| | - Hideo Hosono
- Materials Research Center for Element Strategy, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama 226-8503, Japan
| | - Toshio Kamiya
- Laboratory for Materials and Structures, Institute of Innovative Research, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama 226-8503, Japan.,Materials Research Center for Element Strategy, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama 226-8503, Japan
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12
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Kitamura M, Souma S, Honma A, Wakabayashi D, Tanaka H, Toyoshima A, Amemiya K, Kawakami T, Sugawara K, Nakayama K, Yoshimatsu K, Kumigashira H, Sato T, Horiba K. Development of a versatile micro-focused angle-resolved photoemission spectroscopy system with Kirkpatrick-Baez mirror optics. Rev Sci Instrum 2022; 93:033906. [PMID: 35364976 DOI: 10.1063/5.0074393] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/08/2021] [Accepted: 02/28/2022] [Indexed: 06/14/2023]
Abstract
Angle-resolved photoemission spectroscopy using a micro-focused beam spot [micro-angle-resolved photoemission spectroscopy (ARPES)] is becoming a powerful tool to elucidate key electronic states of exotic quantum materials. We have developed a versatile micro-ARPES system based on the synchrotron radiation beam focused with a Kirkpatrick-Baez mirror optics. The mirrors are monolithically installed on a stage, which is driven with five-axis motion, and are vibrationally separated from the ARPES measurement system. Spatial mapping of the Au photolithography pattern on Si signifies the beam spot size of 10 µm (horizontal) × 12 µm (vertical) at the sample position, which is well suited to resolve the fine structure in local electronic states. Utilization of the micro-beam and the high precision sample motion system enables the accurate spatially resolved band-structure mapping, as demonstrated by the observation of a small band anomaly associated with tiny sample bending near the edge of a cleaved topological insulator single crystal.
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Affiliation(s)
- Miho Kitamura
- Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba 305-0801, Japan
| | - Seigo Souma
- Center for Spintronics Research Network, Tohoku University, Sendai 980-8577, Japan
| | - Asuka Honma
- Department of Physics, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan
| | - Daisuke Wakabayashi
- Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba 305-0801, Japan
| | - Hirokazu Tanaka
- Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba 305-0801, Japan
| | - Akio Toyoshima
- Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba 305-0801, Japan
| | - Kenta Amemiya
- Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba 305-0801, Japan
| | - Tappei Kawakami
- Department of Physics, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan
| | - Katsuaki Sugawara
- Center for Spintronics Research Network, Tohoku University, Sendai 980-8577, Japan
| | - Kosuke Nakayama
- Department of Physics, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan
| | - Kohei Yoshimatsu
- Institute of Multidisciplinary Research for Advanced Materials (IMRAM), Tohoku University, Sendai 980-8577, Japan
| | - Hiroshi Kumigashira
- Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba 305-0801, Japan
| | - Takafumi Sato
- Center for Spintronics Research Network, Tohoku University, Sendai 980-8577, Japan
| | - Koji Horiba
- Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba 305-0801, Japan
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13
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Kimura M, He X, Katase T, Tadano T, Tomczak JM, Minohara M, Aso R, Yoshida H, Ide K, Ueda S, Hiramatsu H, Kumigashira H, Hosono H, Kamiya T. Large phonon drag thermopower boosted by massive electrons and phonon leaking in LaAlO 3/LaNiO 3/LaAlO 3 heterostructure. Nano Lett 2021; 21:9240-9246. [PMID: 34709840 PMCID: PMC8587880 DOI: 10.1021/acs.nanolett.1c03143] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/16/2021] [Revised: 10/11/2021] [Indexed: 06/04/2023]
Abstract
An unusually large thermopower (S) enhancement is induced by heterostructuring thin films of the strongly correlated electron oxide LaNiO3. The phonon-drag effect, which is not observed in bulk LaNiO3, enhances S for thin films compressively strained by LaAlO3 substrates. By a reduction in the layer thickness down to three unit cells and subsequent LaAlO3 surface termination, a 10 times S enhancement over the bulk value is observed due to large phonon drag S (Sg), and the Sg contribution to the total S occurs over a much wider temperature range up to 220 K. The Sg enhancement originates from the coupling of lattice vibration to the d electrons with large effective mass in the compressively strained ultrathin LaNiO3, and the electron-phonon interaction is largely enhanced by the phonon leakage from the LaAlO3 substrate and the capping layer. The transition-metal oxide heterostructures emerge as a new playground to manipulate electronic and phononic properties in the quest for high-performance thermoelectrics.
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Affiliation(s)
- Masatoshi Kimura
- Laboratory
for Materials and Structures, Institute of Innovative Research, Tokyo Institute of Technology, 4259 Nagatsuta, Midori, Yokohama 226-8503, Japan
| | - Xinyi He
- Laboratory
for Materials and Structures, Institute of Innovative Research, Tokyo Institute of Technology, 4259 Nagatsuta, Midori, Yokohama 226-8503, Japan
| | - Takayoshi Katase
- Laboratory
for Materials and Structures, Institute of Innovative Research, Tokyo Institute of Technology, 4259 Nagatsuta, Midori, Yokohama 226-8503, Japan
- PRESTO,
Japan Science and Technology Agency, 7 Gobancho, Chiyoda, Tokyo 102-0076, Japan
| | - Terumasa Tadano
- National
Institute for Materials Science, Sengen, Tsukuba 305-0047, Japan
| | - Jan M. Tomczak
- Institute
of Solid State Physics, Vienna University
of Technology, Wiedner Hauptstrasse 8-10, A-1040 Vienna, Austria
| | - Makoto Minohara
- Research
Institute for Advanced Electronics and Photonics, National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki 305-8568, Japan
| | - Ryotaro Aso
- Department
of Applied Quantum Physics and Nuclear Engineering, Kyushu University, Fukuoka, Fukuoka 819-0395, Japan
| | - Hideto Yoshida
- The
Institute of Scientific and Industrial Research, Osaka University, 8-1 Mihogaoka, Ibaraki, Osaka 567-0047, Japan
| | - Keisuke Ide
- Laboratory
for Materials and Structures, Institute of Innovative Research, Tokyo Institute of Technology, 4259 Nagatsuta, Midori, Yokohama 226-8503, Japan
| | - Shigenori Ueda
- Research
Center for Functional Materials, National
Institute for Materials Science, Namiki, Tsukuba 305-0044, Japan
- Research
Center for Advanced Measurement and Characterization, National Institute for Materials Science, Tsukuba 305-0047, Japan
- Synchrotron
X-ray Station at SPring-8, National Institute
for Materials Science, 1-1-1 Sayo, Hyogo, 679-5148, Japan
| | - Hidenori Hiramatsu
- Laboratory
for Materials and Structures, Institute of Innovative Research, Tokyo Institute of Technology, 4259 Nagatsuta, Midori, Yokohama 226-8503, Japan
- Materials
Research Center for Element Strategy, Tokyo
Institute of Technology, 4259 Nagatsuta, Midori, Yokohama 226-8503, Japan
| | - Hiroshi Kumigashira
- Photon
Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization, Tsukuba, Ibaraki 305-0801, Japan
- Institute
of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai 980-8577, Japan
| | - Hideo Hosono
- Materials
Research Center for Element Strategy, Tokyo
Institute of Technology, 4259 Nagatsuta, Midori, Yokohama 226-8503, Japan
| | - Toshio Kamiya
- Laboratory
for Materials and Structures, Institute of Innovative Research, Tokyo Institute of Technology, 4259 Nagatsuta, Midori, Yokohama 226-8503, Japan
- Materials
Research Center for Element Strategy, Tokyo
Institute of Technology, 4259 Nagatsuta, Midori, Yokohama 226-8503, Japan
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14
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Takane D, Kubota Y, Nakayama K, Kawakami T, Yamauchi K, Souma S, Kato T, Sugawara K, Ideta SI, Tanaka K, Kitamura M, Horiba K, Kumigashira H, Oguchi T, Takahashi T, Segawa K, Sato T. Dirac semimetal phase and switching of band inversion in XMg 2Bi 2 (X = Ba and Sr). Sci Rep 2021; 11:21937. [PMID: 34754019 PMCID: PMC8578568 DOI: 10.1038/s41598-021-01333-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2021] [Accepted: 10/26/2021] [Indexed: 11/22/2022] Open
Abstract
Topological Dirac semimetals (TDSs) offer an excellent opportunity to realize outstanding physical properties distinct from those of topological insulators. Since TDSs verified so far have their own problems such as high reactivity in the atmosphere and difficulty in controlling topological phases via chemical substitution, it is highly desirable to find a new material platform of TDSs. By angle-resolved photoemission spectroscopy combined with first-principles band-structure calculations, we show that ternary compound BaMg2Bi2 is a TDS with a simple Dirac-band crossing around the Brillouin-zone center protected by the C3 symmetry of crystal. We also found that isostructural SrMg2Bi2 is an ordinary insulator characterized by the absence of band inversion due to the reduction of spin–orbit coupling. Thus, XMg2Bi2 (X = Sr, Ba, etc.) serves as a useful platform to study the interplay among crystal symmetry, spin–orbit coupling, and topological phase transition around the TDS phase.
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Affiliation(s)
- Daichi Takane
- Department of Physics, Graduate School of Science, Tohoku University, Sendai, 980-8578, Japan
| | - Yuya Kubota
- Department of Physics, Graduate School of Science, Tohoku University, Sendai, 980-8578, Japan
| | - Kosuke Nakayama
- Department of Physics, Graduate School of Science, Tohoku University, Sendai, 980-8578, Japan. .,Precursory Research for Embryonic Science and Technology (PRESTO), Japan Science and Technology Agency (JST), Tokyo, 102-0076, Japan.
| | - Tappei Kawakami
- Department of Physics, Graduate School of Science, Tohoku University, Sendai, 980-8578, Japan
| | - Kunihiko Yamauchi
- Center for the Promotion of Interdisciplinary Education and Research, Kyoto University, Kyoto, 606-8501, Japan
| | - Seigo Souma
- Center for Spintronics Research Network, Tohoku University, Sendai, 980-8577, Japan.,Advanced Institute for Materials Research (WPI-AIMR), Tohoku University, Sendai, 980-8577, Japan
| | - Takemi Kato
- Department of Physics, Graduate School of Science, Tohoku University, Sendai, 980-8578, Japan
| | - Katsuaki Sugawara
- Department of Physics, Graduate School of Science, Tohoku University, Sendai, 980-8578, Japan.,Precursory Research for Embryonic Science and Technology (PRESTO), Japan Science and Technology Agency (JST), Tokyo, 102-0076, Japan.,Center for Spintronics Research Network, Tohoku University, Sendai, 980-8577, Japan.,Advanced Institute for Materials Research (WPI-AIMR), Tohoku University, Sendai, 980-8577, Japan
| | - Shin-Ichiro Ideta
- UVSOR Synchrotron Facility, Institute for Molecular Science, Okazaki, 444-8585, Japan.,School of Physical Sciences, The Graduate University for Advanced Studies (SOKENDAI), Okazaki, 444-8585, Japan.,Hiroshima Synchrotron Radiation Center, Hiroshima University, Higashi-Hiroshima, 739-0046, Japan
| | - Kiyohisa Tanaka
- UVSOR Synchrotron Facility, Institute for Molecular Science, Okazaki, 444-8585, Japan.,School of Physical Sciences, The Graduate University for Advanced Studies (SOKENDAI), Okazaki, 444-8585, Japan
| | - Miho Kitamura
- Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki, 305-0801, Japan
| | - Koji Horiba
- Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki, 305-0801, Japan.,National Institutes for Quantum and Radiological Science and Technology (QST), Sayo, Hyogo, 679-5148, Japan
| | - Hiroshi Kumigashira
- Institute of Multidisciplinary Research for Advanced Materials (IMRAM), Tohoku University, Sendai, 980-8577, Japan
| | - Tamio Oguchi
- Center for Spintronics Research Network, Osaka University, Toyonaka, 560-8531, Japan.,Institute of Scientific and Industrial Research, Osaka University, Ibaraki, Osaka, 567-0047, Japan
| | - Takashi Takahashi
- Department of Physics, Graduate School of Science, Tohoku University, Sendai, 980-8578, Japan.,Center for Spintronics Research Network, Tohoku University, Sendai, 980-8577, Japan.,Advanced Institute for Materials Research (WPI-AIMR), Tohoku University, Sendai, 980-8577, Japan
| | - Kouji Segawa
- Department of Physics, Kyoto Sangyo University, Kyoto, 603-8555, Japan
| | - Takafumi Sato
- Department of Physics, Graduate School of Science, Tohoku University, Sendai, 980-8578, Japan. .,Center for Spintronics Research Network, Tohoku University, Sendai, 980-8577, Japan. .,Advanced Institute for Materials Research (WPI-AIMR), Tohoku University, Sendai, 980-8577, Japan.
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15
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Thees M, Lee MH, Bouwmeester RL, Rezende-Gonçalves PH, David E, Zimmers A, Fortuna F, Frantzeskakis E, Vargas NM, Kalcheim Y, Le Fèvre P, Horiba K, Kumigashira H, Biermann S, Trastoy J, Rozenberg MJ, Schuller IK, Santander-Syro AF. Imaging the itinerant-to-localized transmutation of electrons across the metal-to-insulator transition in V 2O 3. Sci Adv 2021; 7:eabj1164. [PMID: 34730993 PMCID: PMC8565841 DOI: 10.1126/sciadv.abj1164] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/21/2021] [Accepted: 09/14/2021] [Indexed: 06/13/2023]
Abstract
In solids, strong repulsion between electrons can inhibit their movement and result in a “Mott” metal-to-insulator transition (MIT), a fundamental phenomenon whose understanding has remained a challenge for over 50 years. A key issue is how the wave-like itinerant electrons change into a localized-like state due to increased interactions. However, observing the MIT in terms of the energy- and momentum-resolved electronic structure of the system, the only direct way to probe both itinerant and localized states, has been elusive. Here we show, using angle-resolved photoemission spectroscopy (ARPES), that in V2O3, the temperature-induced MIT is characterized by the progressive disappearance of its itinerant conduction band, without any change in its energy-momentum dispersion, and the simultaneous shift to larger binding energies of a quasi-localized state initially located near the Fermi level.
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Affiliation(s)
- Maximilian Thees
- Université Paris-Saclay, CNRS, Institut des Sciences Moléculaires d'Orsay, 91405 Orsay, France
| | - Min-Han Lee
- Department of Physics and Center for Advanced Nanoscience, University of California San Diego, La Jolla, CA 92093, USA
| | - Rosa Luca Bouwmeester
- Faculty of Science and Technology and MESA+ Institute for Nanotechnology, University of Twente, 7500 AE Enschede, Netherlands
| | - Pedro H. Rezende-Gonçalves
- Université Paris-Saclay, CNRS, Institut des Sciences Moléculaires d'Orsay, 91405 Orsay, France
- Departamento de Física, Universidade Federal de Minas Gerais, Av. Pres. Antonio Carlos, 6627 Belo Horizonte, Brazil
| | - Emma David
- Université Paris-Saclay, CNRS, Institut des Sciences Moléculaires d'Orsay, 91405 Orsay, France
| | - Alexandre Zimmers
- LPEM, ESPCI Paris, PSL Research University, CNRS, Sorbonne Université, 75005 Paris, France
| | - Franck Fortuna
- Université Paris-Saclay, CNRS, Institut des Sciences Moléculaires d'Orsay, 91405 Orsay, France
| | - Emmanouil Frantzeskakis
- Université Paris-Saclay, CNRS, Institut des Sciences Moléculaires d'Orsay, 91405 Orsay, France
| | - Nicolas M. Vargas
- Department of Physics and Center for Advanced Nanoscience, University of California San Diego, La Jolla, CA 92093, USA
| | - Yoav Kalcheim
- Department of Physics and Center for Advanced Nanoscience, University of California San Diego, La Jolla, CA 92093, USA
| | - Patrick Le Fèvre
- Synchrotron SOLEIL, L'Orme des Merisiers, Saint-Aubin-BP48, 91192 Gif-sur-Yvette, France
| | - Koji Horiba
- Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba 305-0801, Japan
| | - Hiroshi Kumigashira
- Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba 305-0801, Japan
- Institute of Multidisciplinary Research for Advanced Materials (IMRAM), Tohoku University, Sendai 980-8577, Japan
| | - Silke Biermann
- CPHT, CNRS, Ecole Polytechnique, Institut Polytechnique de Paris, F-91128 Palaiseau, France
- Collège de France, 11 place Marcelin Berthelot, 75005 Paris, France
- Department of Physics, Division of Mathematical Physics, Lund University, Professorsgatan 1, 22363 Lund, Sweden
| | - Juan Trastoy
- Unité Mixte de Physique, CNRS, Thales, Université Paris-Sud, Université Paris-Saclay, 91767 Palaiseau, France
| | - Marcelo J. Rozenberg
- Université Paris-Saclay, CNRS, Laboratoire de Physique des Solides, 91405 Orsay, France
| | - Ivan K. Schuller
- Department of Physics and Center for Advanced Nanoscience, University of California San Diego, La Jolla, CA 92093, USA
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16
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Minohara M, Dobashi Y, Kikuchi N, Samizo A, Tsukuda K, Nishio K, Mibu K, Kumigashira H, Hase I, Yoshida Y, Aiura Y. Bipolar Semiconducting Properties in α-SnWO 4 Based on the Characteristic Defect Structure. Inorg Chem 2021; 60:8035-8041. [PMID: 34037389 DOI: 10.1021/acs.inorgchem.1c00530] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Diodes, memories, logic circuits, and most other current information technologies rely on the combined use of p- and n-type semiconductors. Although oxide semiconductors have many technologically attractive functionalities, such as transparency and high dopability to enable their use as conducting films, they typically lack bipolar conductivity. In particular, the absence of p-type semiconducting properties owing to the innate electronic structures of oxides represents a bottleneck for the development of practical devices. Here, bipolar semiconducting properties are demonstrated in α-SnWO4 within a 100 °C temperature window after appropriate thermal treatment. Comprehensive spectroscopic observations reveal that Sn4+ is present in p-type α-SnWO4 in a notably greater quantity than in n-type. This result strongly suggests that the Sn4+ substitutional defects on the W6+ sites contribute to hole-carrier generation in α-SnWO4. We also find that oxygen vacancies are initially formed in Sn-O-W bonds and migrate to W-O-W bonds with changes in semiconducting properties from p-type to n-type. These findings suggest useful strategies for exploring p-type oxide semiconductors and controlling their carrier type by utilizing the octahedral structure.
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Affiliation(s)
- Makoto Minohara
- Research Institute for Advanced Electronics and Photonics, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki 305-8568, Japan
| | - Yuka Dobashi
- Department of Materials Science and Technology, Tokyo University of Science, Katsushika, Tokyo 125-8585, Japan
| | - Naoto Kikuchi
- Research Institute for Advanced Electronics and Photonics, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki 305-8568, Japan
| | - Akane Samizo
- Department of Materials Science and Technology, Tokyo University of Science, Katsushika, Tokyo 125-8585, Japan
| | - Kouhei Tsukuda
- Department of Materials Science and Technology, Tokyo University of Science, Katsushika, Tokyo 125-8585, Japan
| | - Keishi Nishio
- Department of Materials Science and Technology, Tokyo University of Science, Katsushika, Tokyo 125-8585, Japan
| | - Ko Mibu
- Department of Physical Science and Engineering, Nagoya Institute of Technology, Nagoya 466-8555, Japan
| | - Hiroshi Kumigashira
- Institute of Multidisciplinary Research for Advanced Materials (IMRAM), Tohoku University, Sendai 980-8577, Japan.,Photon Factory, Institute of Materials Structure Science (IMSS), High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki 305-0801, Japan
| | - Izumi Hase
- Research Institute for Advanced Electronics and Photonics, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki 305-8568, Japan
| | - Yoshiyuki Yoshida
- Research Institute for Advanced Electronics and Photonics, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki 305-8568, Japan
| | - Yoshihiro Aiura
- Research Institute for Advanced Electronics and Photonics, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki 305-8568, Japan
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17
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Endoh N, Akiyama S, Tashima K, Suwa K, Kamogawa T, Kohama R, Funakubo K, Konishi S, Mogi H, Kawahara M, Kawai M, Kubota Y, Ohkochi T, Kotsugi M, Horiba K, Kumigashira H, Suemitsu M, Watanabe I, Fukidome H. High-Quality Few-Layer Graphene on Single-Crystalline SiC thin Film Grown on Affordable Wafer for Device Applications. Nanomaterials (Basel) 2021; 11:nano11020392. [PMID: 33557014 PMCID: PMC7913666 DOI: 10.3390/nano11020392] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/30/2020] [Revised: 01/04/2021] [Accepted: 01/08/2021] [Indexed: 12/04/2022]
Abstract
Graphene is promising for next-generation devices. However, one of the primary challenges in realizing these devices is the scalable growth of high-quality few-layer graphene (FLG) on device-type wafers; it is difficult to do so while balancing both quality and affordability. High-quality graphene is grown on expensive SiC bulk crystals, while graphene on SiC thin films grown on Si substrates (GOS) exhibits low quality but affordable cost. We propose a new method for the growth of high-quality FLG on a new template named “hybrid SiC”. The hybrid SiC is produced by bonding a SiC bulk crystal with an affordable device-type wafer and subsequently peeling off the SiC bulk crystal to obtain a single-crystalline SiC thin film on the wafer. The quality of FLG on this hybrid SiC is comparable to that of FLG on SiC bulk crystals and much higher than of GOS. FLG on the hybrid SiC exhibited high carrier mobilities, comparable to those on SiC bulk crystals, as anticipated from the linear band dispersions. Transistors using FLG on the hybrid SiC showed the potential to operate in terahertz frequencies. The proposed method is suited for growing high-quality FLG on desired substrates with the aim of realizing graphene-based high-speed devices.
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Affiliation(s)
- Norifumi Endoh
- Research Institute of Electrical Communication, Tohoku University, Sendai, Miyagi 980-8577, Japan; (N.E.); (K.T.); (K.S.); (T.K.); (R.K.); (K.F.); (M.S.)
| | - Shoji Akiyama
- Shin-Etsu Chemical Co., Ltd., Chiyoda-ku, Tokyo 100-0004, Japan; (S.A.); (S.K.); (H.M.); (M.K.); (M.K.); (Y.K.)
| | - Keiichiro Tashima
- Research Institute of Electrical Communication, Tohoku University, Sendai, Miyagi 980-8577, Japan; (N.E.); (K.T.); (K.S.); (T.K.); (R.K.); (K.F.); (M.S.)
| | - Kento Suwa
- Research Institute of Electrical Communication, Tohoku University, Sendai, Miyagi 980-8577, Japan; (N.E.); (K.T.); (K.S.); (T.K.); (R.K.); (K.F.); (M.S.)
| | - Takamasa Kamogawa
- Research Institute of Electrical Communication, Tohoku University, Sendai, Miyagi 980-8577, Japan; (N.E.); (K.T.); (K.S.); (T.K.); (R.K.); (K.F.); (M.S.)
| | - Roki Kohama
- Research Institute of Electrical Communication, Tohoku University, Sendai, Miyagi 980-8577, Japan; (N.E.); (K.T.); (K.S.); (T.K.); (R.K.); (K.F.); (M.S.)
| | - Kazutoshi Funakubo
- Research Institute of Electrical Communication, Tohoku University, Sendai, Miyagi 980-8577, Japan; (N.E.); (K.T.); (K.S.); (T.K.); (R.K.); (K.F.); (M.S.)
| | - Shigeru Konishi
- Shin-Etsu Chemical Co., Ltd., Chiyoda-ku, Tokyo 100-0004, Japan; (S.A.); (S.K.); (H.M.); (M.K.); (M.K.); (Y.K.)
| | - Hiroshi Mogi
- Shin-Etsu Chemical Co., Ltd., Chiyoda-ku, Tokyo 100-0004, Japan; (S.A.); (S.K.); (H.M.); (M.K.); (M.K.); (Y.K.)
| | - Minoru Kawahara
- Shin-Etsu Chemical Co., Ltd., Chiyoda-ku, Tokyo 100-0004, Japan; (S.A.); (S.K.); (H.M.); (M.K.); (M.K.); (Y.K.)
| | - Makoto Kawai
- Shin-Etsu Chemical Co., Ltd., Chiyoda-ku, Tokyo 100-0004, Japan; (S.A.); (S.K.); (H.M.); (M.K.); (M.K.); (Y.K.)
| | - Yoshihiro Kubota
- Shin-Etsu Chemical Co., Ltd., Chiyoda-ku, Tokyo 100-0004, Japan; (S.A.); (S.K.); (H.M.); (M.K.); (M.K.); (Y.K.)
| | - Takuo Ohkochi
- Japan Synchrotron Radiation Research Institute, Sayo, Hyogo 679-5198, Japan; (T.O.); (M.K.)
| | - Masato Kotsugi
- Japan Synchrotron Radiation Research Institute, Sayo, Hyogo 679-5198, Japan; (T.O.); (M.K.)
| | - Koji Horiba
- Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization, Tsukuba, Ibaraki 305-0801, Japan; (K.H.); (H.K.)
| | - Hiroshi Kumigashira
- Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization, Tsukuba, Ibaraki 305-0801, Japan; (K.H.); (H.K.)
- Institute of Multidisciplinary Research for Advanced Materials (IMRAM), Tohoku University, Sendai, Miyagi 980-8577, Japan
| | - Maki Suemitsu
- Research Institute of Electrical Communication, Tohoku University, Sendai, Miyagi 980-8577, Japan; (N.E.); (K.T.); (K.S.); (T.K.); (R.K.); (K.F.); (M.S.)
| | - Issei Watanabe
- National Institute of Information and Communication Technology, Koganei, Tokyo 184-8795, Japan;
| | - Hirokazu Fukidome
- Research Institute of Electrical Communication, Tohoku University, Sendai, Miyagi 980-8577, Japan; (N.E.); (K.T.); (K.S.); (T.K.); (R.K.); (K.F.); (M.S.)
- Correspondence:
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18
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Yoshimatsu K, Hasegawa N, Nambu Y, Ishii Y, Wakabayashi Y, Kumigashira H. Metallic ground states of undoped Ti 2O 3 films induced by elongated c-axis lattice constant. Sci Rep 2020; 10:22109. [PMID: 33335175 PMCID: PMC7747712 DOI: 10.1038/s41598-020-79182-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2020] [Accepted: 12/04/2020] [Indexed: 11/09/2022] Open
Abstract
Ti2O3 exhibits unique metal–insulator transition (MIT) at ~ 450 K over a wide temperature range of ~ 150 K. The close relationship between MIT and crystal deformation has been proposed. However, as physical properties are governed by the thermodynamic equilibrium in bulk systems, conducting experimental studies under different lattice deformations remains challenging. Epitaxial thin films can offer high flexibility to accommodate adaptive crystal lattices and provide efficient platforms for investigating the MIT. In this study, we report the synthesis of corundum-type Ti2O3 films on various growth temperatures. We found that the metallic ground states appeared in the films grown at low temperatures. The electronic ground states were further investigated by the electronic-structure calculations. Results suggest that the electrical properties of Ti2O3 films were governed by the c/a ratio of the crystal structure, and the absence of the MIT was attributed to the lattice deformation characterized by an elongated c lattice constant.
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Affiliation(s)
- K Yoshimatsu
- Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai, Miyagi, 980-8577, Japan. .,Materials Research Center for Element Strategy (MCES), Tokyo Institute of Technology, Yokohama, 226-8503, Japan.
| | - N Hasegawa
- Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai, Miyagi, 980-8577, Japan
| | - Y Nambu
- Institute for Materials Research, Tohoku University, Sendai, Miyagi, 980-8577, Japan
| | - Y Ishii
- Department of Physics, Tohoku University, Sendai, Miyagi, 980-8578, Japan
| | - Y Wakabayashi
- Materials Research Center for Element Strategy (MCES), Tokyo Institute of Technology, Yokohama, 226-8503, Japan.,Department of Physics, Tohoku University, Sendai, Miyagi, 980-8578, Japan
| | - H Kumigashira
- Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai, Miyagi, 980-8577, Japan.,Materials Research Center for Element Strategy (MCES), Tokyo Institute of Technology, Yokohama, 226-8503, Japan.,Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba, 305-0801, Japan
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19
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Mitsuishi N, Sugita Y, Bahramy MS, Kamitani M, Sonobe T, Sakano M, Shimojima T, Takahashi H, Sakai H, Horiba K, Kumigashira H, Taguchi K, Miyamoto K, Okuda T, Ishiwata S, Motome Y, Ishizaka K. Switching of band inversion and topological surface states by charge density wave. Nat Commun 2020; 11:2466. [PMID: 32424170 PMCID: PMC7235022 DOI: 10.1038/s41467-020-16290-w] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2019] [Accepted: 04/25/2020] [Indexed: 11/10/2022] Open
Abstract
Topologically nontrivial materials host protected edge states associated with the bulk band inversion through the bulk-edge correspondence. Manipulating such edge states is highly desired for developing new functions and devices practically using their dissipation-less nature and spin-momentum locking. Here we introduce a transition-metal dichalcogenide VTe2, that hosts a charge density wave (CDW) coupled with the band inversion involving V3d and Te5p orbitals. Spin- and angle-resolved photoemission spectroscopy with first-principles calculations reveal the huge anisotropic modification of the bulk electronic structure by the CDW formation, accompanying the selective disappearance of Dirac-type spin-polarized topological surface states that exist in the normal state. Thorough three dimensional investigation of bulk states indicates that the corresponding band inversion at the Brillouin zone boundary dissolves upon the CDW formation, by transforming into anomalous flat bands. Our finding provides a new insight to the topological manipulation of matters by utilizing CDWs' flexible characters to external stimuli.
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Affiliation(s)
- N Mitsuishi
- Department of Applied Physics, The University of Tokyo, Tokyo, 113-8656, Japan
- Quantum-Phase Electronics Center (QPEC), The University of Tokyo, Wako, 113-8656, Japan
| | - Y Sugita
- Department of Applied Physics, The University of Tokyo, Tokyo, 113-8656, Japan
| | - M S Bahramy
- Department of Applied Physics, The University of Tokyo, Tokyo, 113-8656, Japan
- Quantum-Phase Electronics Center (QPEC), The University of Tokyo, Wako, 113-8656, Japan
- RIKEN Center for Emergent Matter Science (CEMS), Wako, 351-0198, Japan
| | - M Kamitani
- Department of Applied Physics, The University of Tokyo, Tokyo, 113-8656, Japan
- Quantum-Phase Electronics Center (QPEC), The University of Tokyo, Wako, 113-8656, Japan
| | - T Sonobe
- Department of Applied Physics, The University of Tokyo, Tokyo, 113-8656, Japan
- Quantum-Phase Electronics Center (QPEC), The University of Tokyo, Wako, 113-8656, Japan
| | - M Sakano
- Department of Applied Physics, The University of Tokyo, Tokyo, 113-8656, Japan
- Quantum-Phase Electronics Center (QPEC), The University of Tokyo, Wako, 113-8656, Japan
| | - T Shimojima
- RIKEN Center for Emergent Matter Science (CEMS), Wako, 351-0198, Japan
| | - H Takahashi
- Division of Materials Physics, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka, 560-8531, Japan
| | - H Sakai
- Department of Physics, Osaka University, Toyonaka, Osaka, 560-0043, Japan
| | - K Horiba
- Condensed Matter Research Center and Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba, 305-0801, Japan
| | - H Kumigashira
- Condensed Matter Research Center and Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba, 305-0801, Japan
| | - K Taguchi
- Hiroshima Synchrotron Radiation Center (HSRC), Hiroshima University, 2-313 Kagamiyama, Higashi-Hiroshima, 739-0046, Japan
| | - K Miyamoto
- Hiroshima Synchrotron Radiation Center (HSRC), Hiroshima University, 2-313 Kagamiyama, Higashi-Hiroshima, 739-0046, Japan
| | - T Okuda
- Hiroshima Synchrotron Radiation Center (HSRC), Hiroshima University, 2-313 Kagamiyama, Higashi-Hiroshima, 739-0046, Japan
| | - S Ishiwata
- Division of Materials Physics, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka, 560-8531, Japan
| | - Y Motome
- Department of Applied Physics, The University of Tokyo, Tokyo, 113-8656, Japan
| | - K Ishizaka
- Department of Applied Physics, The University of Tokyo, Tokyo, 113-8656, Japan.
- Quantum-Phase Electronics Center (QPEC), The University of Tokyo, Wako, 113-8656, Japan.
- RIKEN Center for Emergent Matter Science (CEMS), Wako, 351-0198, Japan.
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20
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Sakano M, Hirayama M, Takahashi T, Akebi S, Nakayama M, Kuroda K, Taguchi K, Yoshikawa T, Miyamoto K, Okuda T, Ono K, Kumigashira H, Ideue T, Iwasa Y, Mitsuishi N, Ishizaka K, Shin S, Miyake T, Murakami S, Sasagawa T, Kondo T. Radial Spin Texture in Elemental Tellurium with Chiral Crystal Structure. Phys Rev Lett 2020; 124:136404. [PMID: 32302163 DOI: 10.1103/physrevlett.124.136404] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/21/2019] [Accepted: 02/10/2020] [Indexed: 06/11/2023]
Abstract
The chiral crystal is characterized by a lack of mirror symmetry and inversion center, resulting in the inequivalent right- and left-handed structures. In the noncentrosymmetric crystal structure, the spin and momentum of electrons are expected to be locked in the reciprocal space with the help of the spin-orbit interaction. To reveal the spin textures of chiral crystals, we investigate the spin and electronic structure in a p-type semiconductor, elemental tellurium, with the simplest chiral structure by using spin- and angle-resolved photoemission spectroscopy. Our data demonstrate that the highest valence band crossing the Fermi level has a spin component parallel to the electron momentum around the Brillouin zone corners. Significantly, we have also confirmed that the spin polarization is reversed in the crystal with the opposite chirality. The results indicate that the spin textures of the right- and left-handed chiral crystals are hedgehoglike, leading to unconventional magnetoelectric effects and nonreciprocal phenomena.
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Affiliation(s)
- M Sakano
- Institute for Solid State Physics (ISSP), The University of Tokyo, Kashiwa 277-8581, Japan
- Quantum-Phase Electronics Center (QPEC) and Department of Applied Physics, The University of Tokyo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - M Hirayama
- Department of Physics, Tokyo Institute of Technology, Meguro-ku, Tokyo 152-8551, Japan
- Tokodai Institute for Element Strategy (TIES), Tokyo Institute of Technology, Meguro-ku, Tokyo 152-8551, Japan
- RIKEN Center for Emergent Matter Science (CEMS), Wako, Saitama 351-0198, Japan
| | - T Takahashi
- Materials and Structures Laboratory (MSL), Tokyo Institute of Technology, Yokohama, Kanagawa 226-8503, Japan
| | - S Akebi
- Institute for Solid State Physics (ISSP), The University of Tokyo, Kashiwa 277-8581, Japan
| | - M Nakayama
- Institute for Solid State Physics (ISSP), The University of Tokyo, Kashiwa 277-8581, Japan
| | - K Kuroda
- Institute for Solid State Physics (ISSP), The University of Tokyo, Kashiwa 277-8581, Japan
| | - K Taguchi
- Graduate School of Science, Hiroshima University, Higashi-Hiroshima, Hiroshima 739-8526, Japan
| | - T Yoshikawa
- Graduate School of Science, Hiroshima University, Higashi-Hiroshima, Hiroshima 739-8526, Japan
| | - K Miyamoto
- Hiroshima Synchrotron Radiation Center (HiSOR), Hiroshima University, Higashi-Hiroshima, Hiroshima 739-0046, Japan
| | - T Okuda
- Hiroshima Synchrotron Radiation Center (HiSOR), Hiroshima University, Higashi-Hiroshima, Hiroshima 739-0046, Japan
| | - K Ono
- Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki 305-0801, Japan
| | - H Kumigashira
- Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki 305-0801, Japan
- Institute of Multidisciplinary Research for Advanced Materials (IMRAM), Tohoku University, Sendai 980-8577, Japan
| | - T Ideue
- Quantum-Phase Electronics Center (QPEC) and Department of Applied Physics, The University of Tokyo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - Y Iwasa
- Quantum-Phase Electronics Center (QPEC) and Department of Applied Physics, The University of Tokyo, Bunkyo-ku, Tokyo 113-8656, Japan
- RIKEN Center for Emergent Matter Science (CEMS), Wako, Saitama 351-0198, Japan
| | - N Mitsuishi
- Quantum-Phase Electronics Center (QPEC) and Department of Applied Physics, The University of Tokyo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - K Ishizaka
- Quantum-Phase Electronics Center (QPEC) and Department of Applied Physics, The University of Tokyo, Bunkyo-ku, Tokyo 113-8656, Japan
- RIKEN Center for Emergent Matter Science (CEMS), Wako, Saitama 351-0198, Japan
| | - S Shin
- Institute for Solid State Physics (ISSP), The University of Tokyo, Kashiwa 277-8581, Japan
| | - T Miyake
- Research Center for Computational Design of Advanced Functional Materials (CD-FMat), AIST, Tsukuba, Ibaraki 305-8568, Japan
| | - S Murakami
- Department of Physics, Tokyo Institute of Technology, Meguro-ku, Tokyo 152-8551, Japan
- Tokodai Institute for Element Strategy (TIES), Tokyo Institute of Technology, Meguro-ku, Tokyo 152-8551, Japan
| | - T Sasagawa
- Materials and Structures Laboratory (MSL), Tokyo Institute of Technology, Yokohama, Kanagawa 226-8503, Japan
| | - Takeshi Kondo
- Institute for Solid State Physics (ISSP), The University of Tokyo, Kashiwa 277-8581, Japan
- AIST-UTokyo Advanced Operando-Measurement Technology Open Innovation Laboratory (OPERANDO-OIL), Kashiwa, Chiba 277-8581, Japan
- Trans-scale Quantum Science Institute, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan
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21
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Nishioka D, Tsuchiya T, Namiki W, Takayanagi M, Kawamura K, Fujita T, Yukawa R, Horiba K, Kumigashira H, Higuchi T. Surface Proton Conduction of Sm-Doped CeO 2-δ Thin Film Preferentially Grown on Al 2O 3 (0001). Nanoscale Res Lett 2020; 15:42. [PMID: 32065313 PMCID: PMC7026374 DOI: 10.1186/s11671-020-3267-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/08/2019] [Accepted: 01/22/2020] [Indexed: 06/10/2023]
Abstract
Sm-doped CeO2-δ (Ce0.9Sm0.1O2-δ; SDC) thin films were prepared on Al2O3 (0001) substrates by radio frequency magnetron sputtering. The prepared thin films were preferentially grown along the [111] direction, with the spacing of the (111) plane (d111) expanded by 2.6% to compensate for a lattice mismatch against the substrate. The wet-annealed SDC thin film, with the reduced d111 value, exhibited surface protonic conduction in the low-temperature region below 100 °C. The O1s photoemission spectrum exhibits H2O and OH- peaks on the SDC surface. These results indicate the presence of physisorbed water layers and the generation of protons on the SDC (111) surface with oxygen vacancies. The protons generated on the SDC surface were conducted through a physisorbed water layer by the Grotthuss mechanism.
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Affiliation(s)
- D Nishioka
- Department of Applied Physics, Tokyo University of Science, Katsushika, Tokyo, 125-8585, Japan.
| | - T Tsuchiya
- International Center for Materials Nanoarchitectonics (WPI-MANA), National Institute for Materials Science (NIMS), Tsukuba, Ibaraki, 305-0044, Japan
| | - W Namiki
- Department of Applied Physics, Tokyo University of Science, Katsushika, Tokyo, 125-8585, Japan
| | - M Takayanagi
- Department of Applied Physics, Tokyo University of Science, Katsushika, Tokyo, 125-8585, Japan
| | - K Kawamura
- Department of Applied Physics, Tokyo University of Science, Katsushika, Tokyo, 125-8585, Japan
| | - T Fujita
- Department of Applied Physics, Tokyo University of Science, Katsushika, Tokyo, 125-8585, Japan
| | - R Yukawa
- Photon Factory, High Energy Accelerator Organization (KEK), Tsukuba, Ibaraki, 305-0801, Japan
| | - K Horiba
- Photon Factory, High Energy Accelerator Organization (KEK), Tsukuba, Ibaraki, 305-0801, Japan
| | - H Kumigashira
- Photon Factory, High Energy Accelerator Organization (KEK), Tsukuba, Ibaraki, 305-0801, Japan
- Institute of Multidisciplinary Research for Advanced Materials (IMRAM), Tohoku University, Sendai, 980-8577, Japan
| | - T Higuchi
- Department of Applied Physics, Tokyo University of Science, Katsushika, Tokyo, 125-8585, Japan
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22
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Kriener M, Sakano M, Kamitani M, Bahramy MS, Yukawa R, Horiba K, Kumigashira H, Ishizaka K, Tokura Y, Taguchi Y. Evolution of Electronic States and Emergence of Superconductivity in the Polar Semiconductor GeTe by Doping Valence-Skipping Indium. Phys Rev Lett 2020; 124:047002. [PMID: 32058775 DOI: 10.1103/physrevlett.124.047002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/05/2019] [Indexed: 06/10/2023]
Abstract
GeTe is a chemically simple IV-VI semiconductor which bears a rich plethora of different physical properties induced by doping and external stimuli. Here, we report a superconductor-semiconductor-superconductor transition controlled by finely-tuned In doping. Our results reveal the existence of a critical doping concentration x_{c}=0.12 in Ge_{1-x}In_{x}Te, where various properties, including structure, resistivity, charge carrier type, and the density of states, take either an extremum or change their character. At the same time, we find indications of a change in the In-valence state from In^{3+} to In^{1+} with increasing x by core-level photoemission spectroscopy, suggesting that this system is a new promising playground to probe valence fluctuations and their possible impact on structural, electronic, and thermodynamic properties of their host.
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Affiliation(s)
- M Kriener
- RIKEN Center for Emergent Matter Science (CEMS), Wako 351-0198, Japan
| | - M Sakano
- Department of Applied Physics and Quantum-Phase Electronics Center (QPEC), University of Tokyo, Tokyo 113-8656, Japan
| | - M Kamitani
- RIKEN Center for Emergent Matter Science (CEMS), Wako 351-0198, Japan
| | - M S Bahramy
- RIKEN Center for Emergent Matter Science (CEMS), Wako 351-0198, Japan
- Department of Applied Physics and Quantum-Phase Electronics Center (QPEC), University of Tokyo, Tokyo 113-8656, Japan
| | - R Yukawa
- Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki 305-0801, Japan
| | - K Horiba
- Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki 305-0801, Japan
| | - H Kumigashira
- Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki 305-0801, Japan
- Institute of Multidisciplinary Research for Advanced Materials (IMRAM), Tohoku University, Sendai 980-8577, Japan
| | - K Ishizaka
- RIKEN Center for Emergent Matter Science (CEMS), Wako 351-0198, Japan
- Department of Applied Physics and Quantum-Phase Electronics Center (QPEC), University of Tokyo, Tokyo 113-8656, Japan
| | - Y Tokura
- RIKEN Center for Emergent Matter Science (CEMS), Wako 351-0198, Japan
- Department of Applied Physics and Quantum-Phase Electronics Center (QPEC), University of Tokyo, Tokyo 113-8656, Japan
- Tokyo College, University of Tokyo, Tokyo 113-8656, Japan
| | - Y Taguchi
- RIKEN Center for Emergent Matter Science (CEMS), Wako 351-0198, Japan
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23
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Wu J, Liu F, Sasase M, Ienaga K, Obata Y, Yukawa R, Horiba K, Kumigashira H, Okuma S, Inoshita T, Hosono H. Natural van der Waals heterostructural single crystals with both magnetic and topological properties. Sci Adv 2019; 5:eaax9989. [PMID: 31763457 PMCID: PMC6858254 DOI: 10.1126/sciadv.aax9989] [Citation(s) in RCA: 57] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/10/2019] [Accepted: 09/17/2019] [Indexed: 05/23/2023]
Abstract
Heterostructures having both magnetism and topology are promising materials for the realization of exotic topological quantum states while challenging in synthesis and engineering. Here, we report natural magnetic van der Waals heterostructures of (MnBi2Te4) m (Bi2Te3) n that exhibit controllable magnetic properties while maintaining their topological surface states. The interlayer antiferromagnetic exchange coupling is gradually weakened as the separation of magnetic layers increases, and an anomalous Hall effect that is well coupled with magnetization and shows ferromagnetic hysteresis was observed below 5 K. The obtained homogeneous heterostructure with atomically sharp interface and intrinsic magnetic properties will be an ideal platform for studying the quantum anomalous Hall effect, axion insulator states, and the topological magnetoelectric effect.
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Affiliation(s)
- Jiazhen Wu
- Materials Research Center for Element Strategy, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503, Japan
| | - Fucai Liu
- Materials Research Center for Element Strategy, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503, Japan
- School of Optoelectronic Science and Engineering, University of Electronic Science and Technology of China, Chengdu 610054, China
| | - Masato Sasase
- Materials Research Center for Element Strategy, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503, Japan
| | - Koichiro Ienaga
- Department of Physics, Tokyo Institute of Technology, 2-12-1 Ohokayama, Meguro-ku, Tokyo 152-8551, Japan
| | - Yukiko Obata
- Photon Factory and Condensed Matter Research Center, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba 305-0801, Japan
| | - Ryu Yukawa
- Photon Factory and Condensed Matter Research Center, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba 305-0801, Japan
| | - Koji Horiba
- Photon Factory and Condensed Matter Research Center, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba 305-0801, Japan
| | - Hiroshi Kumigashira
- Photon Factory and Condensed Matter Research Center, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba 305-0801, Japan
- Institute of Multidisciplinary Research for Advanced Materials (IMRAM), Tohoku University, Sendai 980-8577, Japan
| | - Satoshi Okuma
- Department of Physics, Tokyo Institute of Technology, 2-12-1 Ohokayama, Meguro-ku, Tokyo 152-8551, Japan
| | - Takeshi Inoshita
- Materials Research Center for Element Strategy, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503, Japan
- National Institute for Materials Science, Tsukuba, Ibaraki 305-0044, Japan
| | - Hideo Hosono
- Materials Research Center for Element Strategy, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503, Japan
- Laboratory for Materials and Structures, Institute of Innovative Research, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503, Japan
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24
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Aiura Y, Ozawa K, Tezuka Y, Minohara M, Samizo A, Bando K, Kumigashira H, Mase K. In-gap state generated by La-on-Sr substitutional defects within the bulk of SrTiO 3. Phys Chem Chem Phys 2019; 21:14646-14653. [PMID: 31215560 DOI: 10.1039/c9cp02307k] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Local distortion in the conduction pathway has a significant influence on the conducting properties of oxides. The electronic states induced in the band gap of SrTiO3 by La doping were investigated using photoemission spectroscopy (PES) and soft X-ray emission spectroscopy (SXES); moreover, the local distortion in the conduction pathway was examined using extended X-ray absorption fine structure (EXAFS). An itinerant state and a localized state were observed as a metallic state and an in-gap state, respectively, in the PES spectra and as inelastic peaks in the SXES spectra. This implied that the itinerant state and the in-gap state coexisted within the bulk. From EXAFS results, it was observed that La doped into SrTiO3 substituted Sr and locally distorted the conduction pathway. The results showed that some electrons doped by La-on-Sr substitution are trapped/localized by the local distortion in the conduction pathway, whereas the remaining doped electrons itinerate in the pristine conduction pathway with no distortion.
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Affiliation(s)
- Yoshihiro Aiura
- Electronics and Photonics Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki 305-8568, Japan.
| | - Kenichi Ozawa
- Department of Chemistry, Tokyo Institute of Technology, Meguro, Tokyo 152-8551, Japan
| | - Yasuhisa Tezuka
- Graduate School of Science and Technology, Hirosaki University, Hirosaki, Aomori 036-8561, Japan
| | - Makoto Minohara
- Electronics and Photonics Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki 305-8568, Japan.
| | - Akane Samizo
- Electronics and Photonics Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki 305-8568, Japan. and Department of Materials Science and Technology, Faculty of Industrial Science and Technology, Tokyo University of Science, Katsushika, Tokyo 125-8585, Japan
| | - Kyoko Bando
- Nanomaterials Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki 305-8565, Japan
| | - Hiroshi Kumigashira
- Photon Factory, Institute of Materials Structure Science (IMSS), High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki 305-0801, Japan and Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai 980-8578, Japan
| | - Kazuhiko Mase
- Photon Factory, Institute of Materials Structure Science (IMSS), High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki 305-0801, Japan and SOKENDAI (The Graduate University for Advanced Studies), Tsukuba, Ibaraki 305-0801, Japan
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25
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Takane D, Wang Z, Souma S, Nakayama K, Nakamura T, Oinuma H, Nakata Y, Iwasawa H, Cacho C, Kim T, Horiba K, Kumigashira H, Takahashi T, Ando Y, Sato T. Observation of Chiral Fermions with a Large Topological Charge and Associated Fermi-Arc Surface States in CoSi. Phys Rev Lett 2019; 122:076402. [PMID: 30848650 DOI: 10.1103/physrevlett.122.076402] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/03/2018] [Revised: 11/06/2018] [Indexed: 06/09/2023]
Abstract
Topological semimetals materialize a new state of quantum matter where massless fermions protected by a specific crystal symmetry host exotic quantum phenomena. Distinct from well-known Dirac and Weyl fermions, structurally chiral topological semimetals are predicted to host new types of massless fermions characterized by a large topological charge, whereas such exotic fermions are yet to be experimentally established. Here, by using angle-resolved photoemission spectroscopy, we experimentally demonstrate that a transition-metal silicide CoSi hosts two types of chiral topological fermions, a spin-1 chiral fermion and a double Weyl fermion, in the center and corner of the bulk Brillouin zone, respectively. Intriguingly, we found that the bulk Fermi surfaces are purely composed of the energy bands related to these fermions. We also find the surface states connecting the Fermi surfaces associated with these fermions, suggesting the existence of the predicted Fermi-arc surface states. Our result provides the first experimental evidence for the chiral topological fermions beyond Dirac and Weyl fermions in condensed-matter systems, and paves the pathway toward realizing exotic electronic properties associated with unconventional chiral fermions.
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Affiliation(s)
- Daichi Takane
- Department of Physics, Tohoku University, Sendai 980-8578, Japan
| | - Zhiwei Wang
- Physics Institute II, University of Cologne, 50937 Köln, Germany
| | - Seigo Souma
- Center for Spintronics Research Network, Tohoku University, Sendai 980-8577, Japan
- WPI Research Center, Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
| | - Kosuke Nakayama
- Department of Physics, Tohoku University, Sendai 980-8578, Japan
| | | | - Hikaru Oinuma
- Department of Physics, Tohoku University, Sendai 980-8578, Japan
| | - Yuki Nakata
- Department of Physics, Tohoku University, Sendai 980-8578, Japan
| | - Hideaki Iwasawa
- Diamond Light Source, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0QX, United Kingdom
| | - Cephise Cacho
- Diamond Light Source, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0QX, United Kingdom
| | - Timur Kim
- Diamond Light Source, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0QX, United Kingdom
| | - Koji Horiba
- Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki 305-0801, Japan
| | - Hiroshi Kumigashira
- Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki 305-0801, Japan
- Institute of Multidisciplinary Research for Advanced Materials (IMRAM), Tohoku University, Sendai 980-8577, Japan
| | - Takashi Takahashi
- Department of Physics, Tohoku University, Sendai 980-8578, Japan
- Center for Spintronics Research Network, Tohoku University, Sendai 980-8577, Japan
- WPI Research Center, Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
| | - Yoichi Ando
- Physics Institute II, University of Cologne, 50937 Köln, Germany
| | - Takafumi Sato
- Department of Physics, Tohoku University, Sendai 980-8578, Japan
- Center for Spintronics Research Network, Tohoku University, Sendai 980-8577, Japan
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26
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Fujiwara H, Terashima K, Sunagawa M, Yano Y, Nagayama T, Fukura T, Yoshii F, Matsuura Y, Ogata M, Wakita T, Yaji K, Harasawa A, Kuroda K, Shin S, Horiba K, Kumigashira H, Muraoka Y, Yokoya T. Origins of Thermal Spin Depolarization in Half-Metallic Ferromagnet CrO_{2}. Phys Rev Lett 2018; 121:257201. [PMID: 30608774 DOI: 10.1103/physrevlett.121.257201] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/11/2018] [Revised: 09/30/2018] [Indexed: 06/09/2023]
Abstract
Using high-resolution spin-resolved photoemission spectroscopy, we observe a thermal spin depolarization to which all spin-polarized electrons contribute. Furthermore, we observe a distinct minority spin state near the Fermi level and a corresponding depolarization that seldom contributes to demagnetization. The origin of this depolarization has been identified as the many-body effect characteristic of half-metallic ferromagnets. Our investigation opens an experimental field of itinerant ferromagnetic physics focusing on phenomena with sub-meV energy scale.
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Affiliation(s)
- Hirokazu Fujiwara
- Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan
| | - Kensei Terashima
- Research Institute for Interdisciplinary Science, Okayama University, Okayama 700-8530, Japan
| | - Masanori Sunagawa
- Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan
| | - Yuko Yano
- Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan
| | - Takanobu Nagayama
- Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan
| | - Tetsushi Fukura
- Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan
| | - Fumiya Yoshii
- Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan
| | - Yuka Matsuura
- Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan
| | - Makoto Ogata
- Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan
| | - Takanori Wakita
- Research Institute for Interdisciplinary Science, Okayama University, Okayama 700-8530, Japan
| | - Koichiro Yaji
- Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - Ayumi Harasawa
- Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - Kenta Kuroda
- Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - Shik Shin
- Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - Koji Horiba
- Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba 305-0801, Japan
| | - Hiroshi Kumigashira
- Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba 305-0801, Japan
- Department of Physics, Tohoku University, Sendai, 980-8577, Japan
| | - Yuji Muraoka
- Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan
- Research Institute for Interdisciplinary Science, Okayama University, Okayama 700-8530, Japan
| | - Takayoshi Yokoya
- Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan
- Research Institute for Interdisciplinary Science, Okayama University, Okayama 700-8530, Japan
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27
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Yamamoto S, Omi T, Akai H, Kubota Y, Takahashi Y, Suzuki Y, Hirata Y, Yamamoto K, Yukawa R, Horiba K, Yumoto H, Koyama T, Ohashi H, Owada S, Tono K, Yabashi M, Shigemasa E, Yamamoto S, Kotsugi M, Wadati H, Kumigashira H, Arima T, Shin S, Matsuda I. Element Selectivity in Second-Harmonic Generation of GaFeO_{3} by a Soft-X-Ray Free-Electron Laser. Phys Rev Lett 2018; 120:223902. [PMID: 29906133 DOI: 10.1103/physrevlett.120.223902] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/21/2017] [Indexed: 05/27/2023]
Abstract
Nonlinear optical frequency conversion has been challenged to move down to the extreme ultraviolet and x-ray region. However, the extremely low signals have allowed researchers to only perform transmission experiments of the gas phase or ultrathin films. Here, we report second harmonic generation (SHG) of the reflected beam of a soft x-ray free-electron laser from a solid, which is enhanced by the resonant effect. The observation revealed that the double resonance condition can be met by absorption edges for transition metal oxides in the soft x-ray range, and this suggests that the resonant SHG technique can be applicable to a wide range of materials. We discuss the possibility of element-selective SHG spectroscopy measurements in the soft x-ray range.
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Affiliation(s)
- Sh Yamamoto
- Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - T Omi
- Department of Advanced Materials Science, The University of Tokyo, Kashiwa 277-8561, Japan
| | - H Akai
- Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - Y Kubota
- Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - Y Takahashi
- Tokyo University of Science, Katsushika 125-8585, Japan
| | - Y Suzuki
- Tokyo University of Science, Katsushika 125-8585, Japan
| | - Y Hirata
- Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - K Yamamoto
- Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - R Yukawa
- Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba 305-0801, Japan
| | - K Horiba
- Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba 305-0801, Japan
| | - H Yumoto
- Japan Synchrotron Radiation Research Institute, Sayo, Hyogo 679-5198, Japan
| | - T Koyama
- Japan Synchrotron Radiation Research Institute, Sayo, Hyogo 679-5198, Japan
| | - H Ohashi
- Japan Synchrotron Radiation Research Institute, Sayo, Hyogo 679-5198, Japan
| | - S Owada
- RIKEN SPring-8 Center, Sayo, Hyogo 679-5148, Japan
| | - K Tono
- Japan Synchrotron Radiation Research Institute, Sayo, Hyogo 679-5198, Japan
| | - M Yabashi
- RIKEN SPring-8 Center, Sayo, Hyogo 679-5148, Japan
| | - E Shigemasa
- UVSOR Facility, Institute for Molecular Science, Okazaki 444-8585, Japan
- Sokendai (the Graduate University for Advanced Studies), Okazaki 444- 8585, Japan
| | - S Yamamoto
- Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - M Kotsugi
- Tokyo University of Science, Katsushika 125-8585, Japan
| | - H Wadati
- Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - H Kumigashira
- Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba 305-0801, Japan
| | - T Arima
- Department of Advanced Materials Science, The University of Tokyo, Kashiwa 277-8561, Japan
- RIKEN Center for Emergent Matter Science (CEMS), Wako 351-0198, Japan
| | - S Shin
- Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - I Matsuda
- Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba 277-8581, Japan
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Kobayashi M, Yoshimatsu K, Mitsuhashi T, Kitamura M, Sakai E, Yukawa R, Minohara M, Fujimori A, Horiba K, Kumigashira H. Emergence of Quantum Critical Behavior in Metallic Quantum-Well States of Strongly Correlated Oxides. Sci Rep 2017; 7:16621. [PMID: 29192172 PMCID: PMC5709408 DOI: 10.1038/s41598-017-16666-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2017] [Accepted: 10/05/2017] [Indexed: 11/09/2022] Open
Abstract
Controlling quantum critical phenomena in strongly correlated electron systems, which emerge in the neighborhood of a quantum phase transition, is a major challenge in modern condensed matter physics. Quantum critical phenomena are generated from the delicate balance between long-range order and its quantum fluctuation. So far, the nature of quantum phase transitions has been investigated by changing a limited number of external parameters such as pressure and magnetic field. We propose a new approach for investigating quantum criticality by changing the strength of quantum fluctuation that is controlled by the dimensional crossover in metallic quantum well (QW) structures of strongly correlated oxides. With reducing layer thickness to the critical thickness of metal-insulator transition, crossover from a Fermi liquid to a non-Fermi liquid has clearly been observed in the metallic QW of SrVO3 by in situ angle-resolved photoemission spectroscopy. Non-Fermi liquid behavior with the critical exponent α = 1 is found to emerge in the two-dimensional limit of the metallic QW states, indicating that a quantum critical point exists in the neighborhood of the thickness-dependent Mott transition. These results suggest that artificial QW structures provide a unique platform for investigating novel quantum phenomena in strongly correlated oxides in a controllable fashion.
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Affiliation(s)
- Masaki Kobayashi
- Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba, 305-0801, Japan.
| | - Kohei Yoshimatsu
- Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba, 305-0801, Japan.,Department of Physics, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
| | - Taichi Mitsuhashi
- Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba, 305-0801, Japan.,Department of Physics, Tohoku University, Sendai, 980-8577, Japan
| | - Miho Kitamura
- Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba, 305-0801, Japan
| | - Enju Sakai
- Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba, 305-0801, Japan
| | - Ryu Yukawa
- Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba, 305-0801, Japan
| | - Makoto Minohara
- Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba, 305-0801, Japan
| | - Atsushi Fujimori
- Department of Physics, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
| | - Koji Horiba
- Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba, 305-0801, Japan
| | - Hiroshi Kumigashira
- Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba, 305-0801, Japan. .,Department of Physics, Tohoku University, Sendai, 980-8577, Japan.
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Kuroda K, Tomita T, Suzuki MT, Bareille C, Nugroho AA, Goswami P, Ochi M, Ikhlas M, Nakayama M, Akebi S, Noguchi R, Ishii R, Inami N, Ono K, Kumigashira H, Varykhalov A, Muro T, Koretsune T, Arita R, Shin S, Kondo T, Nakatsuji S. Evidence for magnetic Weyl fermions in a correlated metal. Nat Mater 2017; 16:1090-1095. [PMID: 28967918 DOI: 10.1038/nmat4987] [Citation(s) in RCA: 115] [Impact Index Per Article: 16.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/05/2017] [Accepted: 08/21/2017] [Indexed: 06/07/2023]
Abstract
Weyl fermions have been observed as three-dimensional, gapless topological excitations in weakly correlated, inversion-symmetry-breaking semimetals. However, their realization in spontaneously time-reversal-symmetry-breaking phases of strongly correlated materials has so far remained hypothetical. Here, we report experimental evidence for magnetic Weyl fermions in Mn3Sn, a non-collinear antiferromagnet that exhibits a large anomalous Hall effect, even at room temperature. Detailed comparison between angle-resolved photoemission spectroscopy (ARPES) measurements and density functional theory (DFT) calculations reveals significant bandwidth renormalization and damping effects due to the strong correlation among Mn 3d electrons. Magnetotransport measurements provide strong evidence for the chiral anomaly of Weyl fermions-namely, the emergence of positive magnetoconductance only in the presence of parallel electric and magnetic fields. Since weak magnetic fields (approximately 10 mT) are adequate to control the distribution of Weyl points and the large fictitious fields (equivalent to approximately a few hundred T) produced by them in momentum space, our discovery lays the foundation for a new field of science and technology involving the magnetic Weyl excitations of strongly correlated electron systems such as Mn3Sn.
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Affiliation(s)
- K Kuroda
- Institute for Solid State Physics, University of Tokyo, Kashiwa 277-8581, Japan
| | - T Tomita
- Institute for Solid State Physics, University of Tokyo, Kashiwa 277-8581, Japan
- CREST, Japan Science and Technology Agency (JST), 4-1-8 Honcho Kawaguchi, Saitama 332-0012, Japan
| | - M-T Suzuki
- CREST, Japan Science and Technology Agency (JST), 4-1-8 Honcho Kawaguchi, Saitama 332-0012, Japan
- RIKEN Center for Emergent Matter Science (CEMS), 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - C Bareille
- Institute for Solid State Physics, University of Tokyo, Kashiwa 277-8581, Japan
| | - A A Nugroho
- Institute for Solid State Physics, University of Tokyo, Kashiwa 277-8581, Japan
- Faculty of Mathematics and Natural Sciences, Institut Teknologi Bandung, Jl. Ganesha 10, 40132 Bandung, Indonesia
| | - P Goswami
- Condensed Matter Theory Center and Joint Quantum Institute, Department of Physics, University of Maryland, College Park, Maryland 20742- 4111, USA
- Department of Physics and Astronomy, 2145 Sheridan Road, Evanston, Illinois 60208, USA
| | - M Ochi
- Department of Physics, Osaka University, Machikaneyama-cho, Toyonaka, Osaka 560-0043, Japan
| | - M Ikhlas
- Institute for Solid State Physics, University of Tokyo, Kashiwa 277-8581, Japan
- CREST, Japan Science and Technology Agency (JST), 4-1-8 Honcho Kawaguchi, Saitama 332-0012, Japan
| | - M Nakayama
- Institute for Solid State Physics, University of Tokyo, Kashiwa 277-8581, Japan
| | - S Akebi
- Institute for Solid State Physics, University of Tokyo, Kashiwa 277-8581, Japan
| | - R Noguchi
- Institute for Solid State Physics, University of Tokyo, Kashiwa 277-8581, Japan
| | - R Ishii
- Institute for Solid State Physics, University of Tokyo, Kashiwa 277-8581, Japan
| | - N Inami
- Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki 305-0801, Japan
| | - K Ono
- Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki 305-0801, Japan
| | - H Kumigashira
- Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki 305-0801, Japan
| | - A Varykhalov
- Helmholtz-Zentrum Berlin für Materialien und Energie, Elektronenspeicherring BESSY II, Albert-Einstein-Strasse 15, 12489 Berlin, Germany
| | - T Muro
- Japan Synchrotron Radiation Research Institute (JASRI), 1-1-1 Kouto, Sayo, Hyogo 679-5198, Japan
| | - T Koretsune
- CREST, Japan Science and Technology Agency (JST), 4-1-8 Honcho Kawaguchi, Saitama 332-0012, Japan
- RIKEN Center for Emergent Matter Science (CEMS), 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - R Arita
- CREST, Japan Science and Technology Agency (JST), 4-1-8 Honcho Kawaguchi, Saitama 332-0012, Japan
- RIKEN Center for Emergent Matter Science (CEMS), 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - S Shin
- Institute for Solid State Physics, University of Tokyo, Kashiwa 277-8581, Japan
| | - Takeshi Kondo
- Institute for Solid State Physics, University of Tokyo, Kashiwa 277-8581, Japan
| | - S Nakatsuji
- Institute for Solid State Physics, University of Tokyo, Kashiwa 277-8581, Japan
- CREST, Japan Science and Technology Agency (JST), 4-1-8 Honcho Kawaguchi, Saitama 332-0012, Japan
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Okada Y, Shiau SY, Chang TR, Chang G, Kobayashi M, Shimizu R, Jeng HT, Shiraki S, Kumigashira H, Bansil A, Lin H, Hitosugi T. Quasiparticle Interference on Cubic Perovskite Oxide Surfaces. Phys Rev Lett 2017; 119:086801. [PMID: 28952762 DOI: 10.1103/physrevlett.119.086801] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/25/2016] [Indexed: 06/07/2023]
Abstract
We report the observation of coherent surface states on cubic perovskite oxide SrVO_{3}(001) thin films through spectroscopic-imaging scanning tunneling microscopy. A direct link between the observed quasiparticle interference patterns and the formation of a d_{xy}-derived surface state is supported by first-principles calculations. We show that the apical oxygens on the topmost VO_{2} plane play a critical role in controlling the coherent surface state via modulating orbital state.
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Affiliation(s)
- Yoshinori Okada
- Advanced Institute for Materials Research (AIMR), Tohoku University, Sendai 980-8577, Japan
| | - Shiue-Yuan Shiau
- Centre for Advanced 2D Materials and Graphene Research Centre, National University of Singapore, Singapore 117546, Singapore
- Department of Physics, National University of Singapore, Singapore 117542, Singapore
| | - Tay-Rong Chang
- Department of Physics, National Tsing Hua University, Hsinchu 30013, Taiwan
- Department of Physics, National Cheng Kung University, Tainan 701, Taiwan
| | - Guoqing Chang
- Centre for Advanced 2D Materials and Graphene Research Centre, National University of Singapore, Singapore 117546, Singapore
- Department of Physics, National University of Singapore, Singapore 117542, Singapore
| | - Masaki Kobayashi
- Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba 305-0801, Japan
| | - Ryota Shimizu
- Advanced Institute for Materials Research (AIMR), Tohoku University, Sendai 980-8577, Japan
| | - Horng-Tay Jeng
- Department of Physics, National Tsing Hua University, Hsinchu 30013, Taiwan
- Institute of Physics, Academia Sinica, Taipei 11529, Taiwan
| | - Susumu Shiraki
- Advanced Institute for Materials Research (AIMR), Tohoku University, Sendai 980-8577, Japan
| | - Hiroshi Kumigashira
- Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba 305-0801, Japan
| | - Arun Bansil
- Department of Physics, Northeastern University, Boston, Massachusetts 02115, USA
| | - Hsin Lin
- Centre for Advanced 2D Materials and Graphene Research Centre, National University of Singapore, Singapore 117546, Singapore
- Department of Physics, National University of Singapore, Singapore 117542, Singapore
| | - Taro Hitosugi
- Advanced Institute for Materials Research (AIMR), Tohoku University, Sendai 980-8577, Japan
- Department of Applied Chemistry, Tokyo Institute of Technology, Tokyo 152-8552, Japan
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31
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Onozuka T, Chikamatsu A, Katayama T, Hirose Y, Harayama I, Sekiba D, Ikenaga E, Minohara M, Kumigashira H, Hasegawa T. Reversible Changes in Resistance of Perovskite Nickelate NdNiO 3 Thin Films Induced by Fluorine Substitution. ACS Appl Mater Interfaces 2017; 9:10882-10887. [PMID: 28271708 DOI: 10.1021/acsami.7b00855] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Perovskite nickel oxides are of fundamental as well as technological interest because they show large resistance modulation associated with phase transition as a function of the temperature and chemical composition. Here, the effects of fluorine doping in perovskite nickelate NdNiO3 epitaxial thin films are investigated through a low-temperature reaction with polyvinylidene fluoride as the fluorine source. The fluorine content in the fluorinated NdNiO3-xFx films is controlled with precision by varying the reaction time. The fully fluorinated film (x ≈ 1) is highly insulating and has a bandgap of 2.1 eV, in contrast to NdNiO3, which exhibits metallic transport properties. Hard X-ray photoelectron and soft X-ray absorption spectroscopies reveal the suppression of the density of states at the Fermi level as well as the reduction of nickel ions (valence state changes from +3 to +2) after fluorination, suggesting that the strong Coulombic repulsion in the Ni 3d orbitals associated with the fluorine substitution drives the metal-to-insulator transition. In addition, the resistivity of the fluorinated films recovers to the original value for NdNiO3 after annealing in an oxygen atmosphere. By application of the reversible fluorination process to transition-metal oxides, the search for resistance-switching materials could be accelerated.
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Affiliation(s)
- Tomoya Onozuka
- Department of Chemistry, University of Tokyo , 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Akira Chikamatsu
- Department of Chemistry, University of Tokyo , 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Tsukasa Katayama
- Department of Chemistry, University of Tokyo , 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Yasushi Hirose
- Department of Chemistry, University of Tokyo , 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
- Kanagawa Academy of Science and Technology (KAST) , 3-2-1 Sakado, Takatsu, Kawasaki, Kanagawa 213-0012, Japan
| | - Isao Harayama
- Tandem Accelerator Complex, University of Tsukuba , 1-1-1 Tennoudai, Tsukuba, Ibaraki 305-8577, Japan
| | - Daiichiro Sekiba
- Tandem Accelerator Complex, University of Tsukuba , 1-1-1 Tennoudai, Tsukuba, Ibaraki 305-8577, Japan
| | - Eiji Ikenaga
- Japan Synchrotron Radiation Research Institute (JASRI)/SPring-8 , 1-1-1 Kouto, Mikazuki-cho, Hyogo 679-5198, Japan
| | - Makoto Minohara
- Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK) , 1-1 Oho, Tsukuba, Ibaraki 305-0801, Japan
| | - Hiroshi Kumigashira
- Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK) , 1-1 Oho, Tsukuba, Ibaraki 305-0801, Japan
| | - Tetsuya Hasegawa
- Department of Chemistry, University of Tokyo , 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
- Kanagawa Academy of Science and Technology (KAST) , 3-2-1 Sakado, Takatsu, Kawasaki, Kanagawa 213-0012, Japan
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32
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Feng B, Sugino O, Liu RY, Zhang J, Yukawa R, Kawamura M, Iimori T, Kim H, Hasegawa Y, Li H, Chen L, Wu K, Kumigashira H, Komori F, Chiang TC, Meng S, Matsuda I. Dirac Fermions in Borophene. Phys Rev Lett 2017; 118:096401. [PMID: 28306312 DOI: 10.1103/physrevlett.118.096401] [Citation(s) in RCA: 65] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/24/2016] [Indexed: 05/12/2023]
Abstract
Honeycomb structures of group IV elements can host massless Dirac fermions with nontrivial Berry phases. Their potential for electronic applications has attracted great interest and spurred a broad search for new Dirac materials especially in monolayer structures. We present a detailed investigation of the β_{12} sheet, which is a borophene structure that can form spontaneously on a Ag(111) surface. Our tight-binding analysis revealed that the lattice of the β_{12} sheet could be decomposed into two triangular sublattices in a way similar to that for a honeycomb lattice, thereby hosting Dirac cones. Furthermore, each Dirac cone could be split by introducing periodic perturbations representing overlayer-substrate interactions. These unusual electronic structures were confirmed by angle-resolved photoemission spectroscopy and validated by first-principles calculations. Our results suggest monolayer boron as a new platform for realizing novel high-speed low-dissipation devices.
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Affiliation(s)
- Baojie Feng
- Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - Osamu Sugino
- Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - Ro-Ya Liu
- Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - Jin Zhang
- Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Ryu Yukawa
- Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki 305-0801, Japan
| | - Mitsuaki Kawamura
- Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - Takushi Iimori
- Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - Howon Kim
- Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - Yukio Hasegawa
- Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - Hui Li
- Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Lan Chen
- Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Kehui Wu
- Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- Collaborative Innovation Center of Quantum Matter, Beijing 100871, China
| | - Hiroshi Kumigashira
- Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki 305-0801, Japan
| | - Fumio Komori
- Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - Tai-Chang Chiang
- Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba 277-8581, Japan
- Department of Physics, University of Illinois, Urbana, Illinois 61801, USA
| | - Sheng Meng
- Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- Collaborative Innovation Center of Quantum Matter, Beijing 100871, China
| | - Iwao Matsuda
- Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba 277-8581, Japan
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Takayanagi M, Furuichi S, Namiki W, Tsuchiya T, Minohara M, Kobayashi M, Horiba K, Kumigashira H, Higuchi T. Proton Conduction on YSZ Electrolyte Thin Films Prepared by RF Magnetron Sputtering. ACTA ACUST UNITED AC 2017. [DOI: 10.1149/07542.0115ecst] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Takayanagi M, Tsuchiya T, Minohara M, Kobayashi M, Horiba K, Kumigashira H, Higuchi T. Surface Electronic Structure of Proton-doped YSZ Thin Film by Soft-X-ray Photoemission Spectroscopy. ACTA ACUST UNITED AC 2017. [DOI: 10.14723/tmrsj.42.61] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
| | - Takashi Tsuchiya
- International Center for Materials Nanoarchitectonics (WPI-MANA), National Institute for Materials Science (NIMS)
| | | | | | | | | | - Tohru Higuchi
- Department of Applied Physics, Tokyo University of Science
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35
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Watarai K, Yoshimatsu K, Horiba K, Kumigashira H, Sakata O, Ohtomo A. Epitaxial synthesis and physical properties of double-perovskite oxide Sr2CoRuO6 thin films. J Phys Condens Matter 2016; 28:436005. [PMID: 27603328 DOI: 10.1088/0953-8984/28/43/436005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
We report epitaxial structures and physical properties of double-perovskite Sr2CoRuO6 films grown using pulsed-laser deposition. Samples with a degree of Co/Ru order of 2-73% were obtained by changing growth temperature. X-ray absorption spectroscopy (XAS) on the highest ordered sample revealed that Co ions were trivalent with a high-spin configuration and Ru ions were pentavalent. We found large differences in magnetization and resistivity between the highest and lowest ordered samples as well as the absence of strong magnetism and metallicity, which are common characteristics of SrCoO3 and SrRuO3. Using resonant photoemission spectroscopy and XAS, dominant d-orbital components at the top of the occupied state (the bottom of the unoccupied state) were identified to be Ru 4d t 2g (Co 3d and Ru 4d t 2g ). These results suggest that the ground state of double-perovskite Sr2CoRuO6 is a ferrimagnetic insulator.
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Affiliation(s)
- K Watarai
- Department of Chemical Science and Engineering, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8552, Japan
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Nakayama M, Kondo T, Tian Z, Ishikawa JJ, Halim M, Bareille C, Malaeb W, Kuroda K, Tomita T, Ideta S, Tanaka K, Matsunami M, Kimura S, Inami N, Ono K, Kumigashira H, Balents L, Nakatsuji S, Shin S. Slater to Mott Crossover in the Metal to Insulator Transition of Nd_{2}Ir_{2}O_{7}. Phys Rev Lett 2016; 117:056403. [PMID: 27517783 DOI: 10.1103/physrevlett.117.056403] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/18/2016] [Indexed: 06/06/2023]
Abstract
We present an angle-resolved photoemission study of the electronic structure of the three-dimensional pyrochlore iridate Nd_{2}Ir_{2}O_{7} through its magnetic metal-insulator transition. Our data reveal that metallic Nd_{2}Ir_{2}O_{7} has a quadratic band, touching the Fermi level at the Γ point, similar to that of Pr_{2}Ir_{2}O_{7}. The Fermi node state is, therefore, a common feature of the metallic phase of the pyrochlore iridates. Upon cooling below the transition temperature, this compound exhibits a gap opening with an energy shift of quasiparticle peaks like a band gap insulator. The quasiparticle peaks are strongly suppressed, however, with further decrease of temperature, and eventually vanish at the lowest temperature, leaving a nondispersive flat band lacking long-lived electrons. We thereby identify a remarkable crossover from Slater to Mott insulators with decreasing temperature. These observations explain the puzzling absence of Weyl points in this material, despite its proximity to the zero temperature metal-insulator transition.
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Affiliation(s)
- M Nakayama
- ISSP, University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - Takeshi Kondo
- ISSP, University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - Z Tian
- ISSP, University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - J J Ishikawa
- ISSP, University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - M Halim
- ISSP, University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - C Bareille
- ISSP, University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - W Malaeb
- ISSP, University of Tokyo, Kashiwa, Chiba 277-8581, Japan
- Physics Department, Faculty of Science, Beirut Arab University, Beirut 11-5020, Lebanon
| | - K Kuroda
- ISSP, University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - T Tomita
- ISSP, University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - S Ideta
- UVSOR Facility, Institute for Molecular Science, Okazaki 444-8585, Japan
| | - K Tanaka
- UVSOR Facility, Institute for Molecular Science, Okazaki 444-8585, Japan
| | - M Matsunami
- Toyota Technological Institute, Nagoya 468-8511, Japan
| | - S Kimura
- Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka 565-0871, Japan
| | - N Inami
- Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki 305-0801, Japan
| | - K Ono
- Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki 305-0801, Japan
| | - H Kumigashira
- Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki 305-0801, Japan
| | - L Balents
- Kavli Institute for Theoretical Physics, Santa Barbara, California 93106, USA
| | - S Nakatsuji
- ISSP, University of Tokyo, Kashiwa, Chiba 277-8581, Japan
- CREST, Japan Science and Technology Agency (JST), 4-1-8 Honcho Kawaguchi, Saitama 332-0012, Japan
| | - S Shin
- ISSP, University of Tokyo, Kashiwa, Chiba 277-8581, Japan
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37
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Kawasaki S, Takahashi R, Yamamoto T, Kobayashi M, Kumigashira H, Yoshinobu J, Komori F, Kudo A, Lippmaa M. Photoelectrochemical water splitting enhanced by self-assembled metal nanopillars embedded in an oxide semiconductor photoelectrode. Nat Commun 2016; 7:11818. [PMID: 27255209 PMCID: PMC4895796 DOI: 10.1038/ncomms11818] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2015] [Accepted: 05/03/2016] [Indexed: 11/17/2022] Open
Abstract
Production of chemical fuels by direct solar energy conversion in a photoelectrochemical cell is of great practical interest for developing a sustainable energy system. Various nanoscale designs such as nanowires, nanotubes, heterostructures and nanocomposites have been explored to increase the energy conversion efficiency of photoelectrochemical water splitting. Here we demonstrate a self-organized nanocomposite material concept for enhancing the efficiency of photocarrier separation and electrochemical energy conversion. Mechanically robust photoelectrodes are formed by embedding self-assembled metal nanopillars in a semiconductor thin film, forming tubular Schottky junctions around each pillar. The photocarrier transport efficiency is strongly enhanced in the Schottky space charge regions while the pillars provide an efficient charge extraction path. Ir-doped SrTiO3 with embedded iridium metal nanopillars shows good operational stability in a water oxidation reaction and achieves over 80% utilization of photogenerated carriers under visible light in the 400- to 600-nm wavelength range. Nanoscale designs are known to increase the energy conversion efficiency of photoelectrochemical water splitting. Here, the authors report a self-organized nanocomposite formed by embedding self-assembled metal nanopillars in a semiconductor thin film, for enhanced photocarrier separation efficiency.
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Affiliation(s)
- Seiji Kawasaki
- Institute for Solid State Physics (ISSP), University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa 277-8581, Japan
| | - Ryota Takahashi
- Institute for Solid State Physics (ISSP), University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa 277-8581, Japan
| | - Takahisa Yamamoto
- Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603, Japan
| | - Masaki Kobayashi
- Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba 305-0801, Japan
| | - Hiroshi Kumigashira
- Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba 305-0801, Japan
| | - Jun Yoshinobu
- Institute for Solid State Physics (ISSP), University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa 277-8581, Japan
| | - Fumio Komori
- Institute for Solid State Physics (ISSP), University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa 277-8581, Japan
| | - Akihiko Kudo
- Department of Applied Chemistry, Faculty of Science, Tokyo University of Science, 1-3 Kagurazaka, Tokyo 162-8601, Japan.,Photocatalysis International Research Center, Research Institute for Science and Technology, Tokyo University of Science, 2641 Noda, Yamazaki 278-8510, Japan
| | - Mikk Lippmaa
- Institute for Solid State Physics (ISSP), University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa 277-8581, Japan
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38
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Horiba K, Kitamura M, Yoshimatsu K, Minohara M, Sakai E, Kobayashi M, Fujimori A, Kumigashira H. Isotropic Kink and Quasiparticle Excitations in the Three-Dimensional Perovskite Manganite La_{0.6}Sr_{0.4}MnO_{3}. Phys Rev Lett 2016; 116:076401. [PMID: 26943547 DOI: 10.1103/physrevlett.116.076401] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/29/2015] [Indexed: 06/05/2023]
Abstract
In order to reveal the many-body interactions in three-dimensional perovskite manganites that show colossal magnetoresistance, we performed an in situ angle-resolved photoemission spectroscopy on La_{0.6}Sr_{0.4}MnO_{3} and investigated the behavior of quasiparticles. We observed quasiparticle peaks near the Fermi momentum in both the electron and the hole bands, and clear kinks throughout the entire hole Fermi surface in the band dispersion. This isotropic behavior of quasiparticles and kinks suggests that polaronic quasiparticles produced by the coupling of electrons with Jahn-Teller phonons play an important role in the colossal magnetoresistance properties of the ferromagnetic metallic phase of three-dimensional manganites.
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Affiliation(s)
- Koji Horiba
- Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba 305-0801, Japan
| | - Miho Kitamura
- Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba 305-0801, Japan
| | - Kohei Yoshimatsu
- Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba 305-0801, Japan
- Department of Physics, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Makoto Minohara
- Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba 305-0801, Japan
| | - Enju Sakai
- Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba 305-0801, Japan
| | - Masaki Kobayashi
- Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba 305-0801, Japan
| | - Atsushi Fujimori
- Department of Physics, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Hiroshi Kumigashira
- Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba 305-0801, Japan
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39
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Kondo T, Nakayama M, Chen R, Ishikawa JJ, Moon EG, Yamamoto T, Ota Y, Malaeb W, Kanai H, Nakashima Y, Ishida Y, Yoshida R, Yamamoto H, Matsunami M, Kimura S, Inami N, Ono K, Kumigashira H, Nakatsuji S, Balents L, Shin S. Quadratic Fermi node in a 3D strongly correlated semimetal. Nat Commun 2015; 6:10042. [PMID: 26640114 PMCID: PMC4686656 DOI: 10.1038/ncomms10042] [Citation(s) in RCA: 126] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2015] [Accepted: 10/29/2015] [Indexed: 11/25/2022] Open
Abstract
Strong spin–orbit coupling fosters exotic electronic states such as topological insulators and superconductors, but the combination of strong spin–orbit and strong electron–electron interactions is just beginning to be understood. Central to this emerging area are the 5d transition metal iridium oxides. Here, in the pyrochlore iridate Pr2Ir2O7, we identify a non-trivial state with a single-point Fermi node protected by cubic and time-reversal symmetries, using a combination of angle-resolved photoemission spectroscopy and first-principles calculations. Owing to its quadratic dispersion, the unique coincidence of four degenerate states at the Fermi energy, and strong Coulomb interactions, non-Fermi liquid behaviour is predicted, for which we observe some evidence. Our discovery implies that Pr2Ir2O7 is a parent state that can be manipulated to produce other strongly correlated topological phases, such as topological Mott insulator, Weyl semimetal, and quantum spin and anomalous Hall states. 5d transition metal iridates provide a platform to study the combined effects of strong spin orbit coupling and strong electronic correlations. Here, the authors find a quadratic band touching in the band structure of Pr2Ir2O7, suggesting it may be tuned to form various strongly correlated topological phases.
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Affiliation(s)
- Takeshi Kondo
- ISSP, University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - M Nakayama
- ISSP, University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - R Chen
- Physics Department, University of California, Santa Barbara, California 93106, USA.,Physics Department, University of California, Berkeley, California 94720, USA.,Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - J J Ishikawa
- ISSP, University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - E-G Moon
- Physics Department, University of California, Santa Barbara, California 93106, USA.,Department of Physics, Korea Advanced Institute of Science and Technology, Daejeon 305-701, Korea
| | - T Yamamoto
- ISSP, University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - Y Ota
- ISSP, University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - W Malaeb
- ISSP, University of Tokyo, Kashiwa, Chiba 277-8581, Japan.,Physics Department, Faculty of Science, Beirut Arab University, P. O. Box 11-5020 Beirut, Lebanon
| | - H Kanai
- ISSP, University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - Y Nakashima
- ISSP, University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - Y Ishida
- ISSP, University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - R Yoshida
- ISSP, University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - H Yamamoto
- ISSP, University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - M Matsunami
- UVSOR Facility, Institute for Molecular Science, Okazaki 444-8585, Japan.,Energy Materials Laboratory, Toyota Technological Institute, Nagoya 468-8511, Japan
| | - S Kimura
- UVSOR Facility, Institute for Molecular Science, Okazaki 444-8585, Japan.,Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka 565-0871, Japan
| | - N Inami
- Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki 305-0801, Japan
| | - K Ono
- Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki 305-0801, Japan
| | - H Kumigashira
- Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki 305-0801, Japan
| | - S Nakatsuji
- ISSP, University of Tokyo, Kashiwa, Chiba 277-8581, Japan.,PRESTO, Japan Science and Technology Agency (JST), 4-1-8 Honcho Kawaguchi, Saitama 332-0012, Japan
| | - L Balents
- Kavli Institute for Theoretical Physics, Santa Barbara, California 93106, USA
| | - S Shin
- ISSP, University of Tokyo, Kashiwa, Chiba 277-8581, Japan
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40
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Kobayashi M, Yoshimatsu K, Sakai E, Kitamura M, Horiba K, Fujimori A, Kumigashira H. Origin of the Anomalous Mass Renormalization in Metallic Quantum Well States of Strongly Correlated Oxide SrVO_{3}. Phys Rev Lett 2015; 115:076801. [PMID: 26317738 DOI: 10.1103/physrevlett.115.076801] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/04/2014] [Indexed: 06/04/2023]
Abstract
In situ angle-resolved photoemission spectroscopy (ARPES) has been performed on SrVO_{3} ultrathin films, which show metallic quantum well (QW) states, to unveil the origin of the anomalous mass enhancement in the QW subbands. The line-shape analysis of the ARPES spectra reveals that the strength of the electron correlation increases as the subband bottom energy approaches the Fermi level. These results indicate that the anomalous subband-dependent mass enhancement mainly arises from the quasi-one-dimensional character of confined V 3d states as a result of their orbital-selective quantization.
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Affiliation(s)
- Masaki Kobayashi
- Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba 305-0801, Japan
| | - Kohei Yoshimatsu
- Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba 305-0801, Japan
- Department of Physics, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Enju Sakai
- Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba 305-0801, Japan
| | - Miho Kitamura
- Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba 305-0801, Japan
| | - Koji Horiba
- Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba 305-0801, Japan
| | - Atsushi Fujimori
- Department of Physics, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Hiroshi Kumigashira
- Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba 305-0801, Japan
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41
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Yajima T, Minohara M, Bell C, Kumigashira H, Oshima M, Hwang HY, Hikita Y. Enhanced electrical transparency by ultrathin LaAlO3 insertion at oxide metal/semiconductor heterointerfaces. Nano Lett 2015; 15:1622-1626. [PMID: 25654211 DOI: 10.1021/nl504169m] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We demonstrate that the electrical conductivity of metal/semiconductor oxide heterojunctions can be increased over 7 orders of magnitude by inserting an ultrathin layer of LaAlO3. This counterintuitive result, that an interfacial barrier can be driven transparent by inserting a wide-gap insulator, arises from the large internal electric field between the two polar LaAlO3 surfaces. This field modifies the effective band offset in the device, highlighting the ability to design the electrostatic boundary conditions with atomic precision.
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Affiliation(s)
- Takeaki Yajima
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory , Menlo Park, California 94025, United States
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42
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Yoshida T, Ideta S, Shimojima T, Malaeb W, Shinada K, Suzuki H, Nishi I, Fujimori A, Ishizaka K, Shin S, Nakashima Y, Anzai H, Arita M, Ino A, Namatame H, Taniguchi M, Kumigashira H, Ono K, Kasahara S, Shibauchi T, Terashima T, Matsuda Y, Nakajima M, Uchida S, Tomioka Y, Ito T, Kihou K, Lee CH, Iyo A, Eisaki H, Ikeda H, Arita R, Saito T, Onari S, Kontani H. Anisotropy of the superconducting gap in the iron-based superconductor BaFe2(As(1-x)P(x))2. Sci Rep 2014; 4:7292. [PMID: 25465027 PMCID: PMC4252890 DOI: 10.1038/srep07292] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2014] [Accepted: 11/14/2014] [Indexed: 11/22/2022] Open
Abstract
We report peculiar momentum-dependent anisotropy in the superconducting gap observed by angle-resolved photoemission spectroscopy in BaFe2(As1-xPx)2 (x = 0.30, Tc = 30 K). Strongly anisotropic gap has been found only in the electron Fermi surface while the gap on the entire hole Fermi surfaces are nearly isotropic. These results are inconsistent with horizontal nodes but are consistent with modified s± gap with nodal loops. We have shown that the complicated gap modulation can be theoretically reproduced by considering both spin and orbital fluctuations.
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Affiliation(s)
- T Yoshida
- 1] Department of Physics, University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan [2] JST, Transformative Research-Project on Iron Pnictides (TRIP), Chiyoda, Tokyo 102-0075, Japan
| | - S Ideta
- Department of Physics, University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - T Shimojima
- Department of Applied Physics, University of Tokyo, Tokyo 113-8656, Japan
| | - W Malaeb
- Institute of Solid State Physics, University of Tokyo, Kashiwa 277-8581, Japan
| | - K Shinada
- Department of Applied Physics, University of Tokyo, Tokyo 113-8656, Japan
| | - H Suzuki
- Department of Physics, University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - I Nishi
- Department of Physics, University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - A Fujimori
- 1] Department of Physics, University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan [2] JST, Transformative Research-Project on Iron Pnictides (TRIP), Chiyoda, Tokyo 102-0075, Japan
| | - K Ishizaka
- Department of Applied Physics, University of Tokyo, Tokyo 113-8656, Japan
| | - S Shin
- Institute of Solid State Physics, University of Tokyo, Kashiwa 277-8581, Japan
| | - Y Nakashima
- Graduate School of Science, Hiroshima University, Higashi-Hiroshima 739-8526, Japan
| | - H Anzai
- Hiroshima Synchrotron Radiation Center, Hiroshima University, Higashi-Hiroshima 739-0046, Japan
| | - M Arita
- Hiroshima Synchrotron Radiation Center, Hiroshima University, Higashi-Hiroshima 739-0046, Japan
| | - A Ino
- Graduate School of Science, Hiroshima University, Higashi-Hiroshima 739-8526, Japan
| | - H Namatame
- Hiroshima Synchrotron Radiation Center, Hiroshima University, Higashi-Hiroshima 739-0046, Japan
| | - M Taniguchi
- 1] Graduate School of Science, Hiroshima University, Higashi-Hiroshima 739-8526, Japan [2] Hiroshima Synchrotron Radiation Center, Hiroshima University, Higashi-Hiroshima 739-0046, Japan
| | - H Kumigashira
- KEK, Photon Factory, Tsukuba, Ibaraki 305-0801, Japan
| | - K Ono
- KEK, Photon Factory, Tsukuba, Ibaraki 305-0801, Japan
| | - S Kasahara
- 1] Research Center for Low Temperature and Materials Sciences, Kyoto University, Kyoto 606-8502, Japan [2] Department of Physics, Kyoto University, Kyoto 606-8502, Japan
| | - T Shibauchi
- Department of Physics, Kyoto University, Kyoto 606-8502, Japan
| | - T Terashima
- Research Center for Low Temperature and Materials Sciences, Kyoto University, Kyoto 606-8502, Japan
| | - Y Matsuda
- Department of Physics, Kyoto University, Kyoto 606-8502, Japan
| | - M Nakajima
- Department of Physics, University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - S Uchida
- 1] Department of Physics, University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan [2] JST, Transformative Research-Project on Iron Pnictides (TRIP), Chiyoda, Tokyo 102-0075, Japan
| | - Y Tomioka
- 1] JST, Transformative Research-Project on Iron Pnictides (TRIP), Chiyoda, Tokyo 102-0075, Japan [2] National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba 305-8568, Japan
| | - T Ito
- 1] JST, Transformative Research-Project on Iron Pnictides (TRIP), Chiyoda, Tokyo 102-0075, Japan [2] National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba 305-8568, Japan
| | - K Kihou
- 1] JST, Transformative Research-Project on Iron Pnictides (TRIP), Chiyoda, Tokyo 102-0075, Japan [2] National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba 305-8568, Japan
| | - C H Lee
- 1] JST, Transformative Research-Project on Iron Pnictides (TRIP), Chiyoda, Tokyo 102-0075, Japan [2] National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba 305-8568, Japan
| | - A Iyo
- 1] JST, Transformative Research-Project on Iron Pnictides (TRIP), Chiyoda, Tokyo 102-0075, Japan [2] National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba 305-8568, Japan
| | - H Eisaki
- 1] JST, Transformative Research-Project on Iron Pnictides (TRIP), Chiyoda, Tokyo 102-0075, Japan [2] National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba 305-8568, Japan
| | - H Ikeda
- 1] JST, Transformative Research-Project on Iron Pnictides (TRIP), Chiyoda, Tokyo 102-0075, Japan [2] Department of Physics, Kyoto University, Kyoto 606-8502, Japan
| | - R Arita
- 1] JST, Transformative Research-Project on Iron Pnictides (TRIP), Chiyoda, Tokyo 102-0075, Japan [2] Department of Applied Physics, University of Tokyo, Tokyo 113-8656, Japan
| | - T Saito
- 1] JST, Transformative Research-Project on Iron Pnictides (TRIP), Chiyoda, Tokyo 102-0075, Japan [2] Department of Physics, Nagoya University, Furo-cho, Nagoya 464-8602, Japan
| | - S Onari
- 1] JST, Transformative Research-Project on Iron Pnictides (TRIP), Chiyoda, Tokyo 102-0075, Japan [2] Department of Applied Physics, Nagoya University, Furo-cho, Nagoya 464-8602, Japan
| | - H Kontani
- 1] JST, Transformative Research-Project on Iron Pnictides (TRIP), Chiyoda, Tokyo 102-0075, Japan [2] Department of Physics, Nagoya University, Furo-cho, Nagoya 464-8602, Japan
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43
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Sunagawa M, Ishiga T, Tsubota K, Jabuchi T, Sonoyama J, Iba K, Kudo K, Nohara M, Ono K, Kumigashira H, Matsushita T, Arita M, Shimada K, Namatame H, Taniguchi M, Wakita T, Muraoka Y, Yokoya T. Characteristic two-dimensional Fermi surface topology of high-Tc iron-based superconductors. Sci Rep 2014; 4:4381. [PMID: 24625746 PMCID: PMC3953724 DOI: 10.1038/srep04381] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2013] [Accepted: 02/24/2014] [Indexed: 11/09/2022] Open
Abstract
Unconventional Cooper pairing originating from spin or orbital fluctuations has been proposed for iron-based superconductors. Such pairing may be enhanced by quasi-nesting of two-dimensional electron and hole-like Fermi surfaces (FS), which is considered an important ingredient for superconductivity at high critical temperatures (high-Tc). However, the dimensionality of the FS varies for hole and electron-doped systems, so the precise importance of this feature for high-Tc materials remains unclear. Here we demonstrate a phase of electron-doped CaFe2As2 (La and P co-doped CaFe2As2) with Tc = 45 K, which is the highest Tc found for the AEFe2As2 bulk superconductors (122-type; AE = Alkaline Earth), possesses only cylindrical hole- and electron-like FSs. This result indicates that FS topology consisting only of two-dimensional sheets is characteristic of both hole- and electron-doped 122-type high-Tc superconductors.
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Affiliation(s)
- Masanori Sunagawa
- 1] The Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan [2] Research Laboratory for Surface Science, Okayama University, 3-1-1 Tsushima-naka, Okayama 700-8530, Japan
| | - Toshihiko Ishiga
- 1] The Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan [2] Research Laboratory for Surface Science, Okayama University, 3-1-1 Tsushima-naka, Okayama 700-8530, Japan
| | - Koji Tsubota
- 1] The Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan [2] Research Laboratory for Surface Science, Okayama University, 3-1-1 Tsushima-naka, Okayama 700-8530, Japan
| | - Taihei Jabuchi
- 1] The Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan [2] Research Laboratory for Surface Science, Okayama University, 3-1-1 Tsushima-naka, Okayama 700-8530, Japan
| | - Junki Sonoyama
- 1] The Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan [2] Research Laboratory for Surface Science, Okayama University, 3-1-1 Tsushima-naka, Okayama 700-8530, Japan
| | - Keita Iba
- 1] The Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan [2] Department of Physics, Okayama University, Okayama 700-8530, Japan
| | - Kazutaka Kudo
- 1] The Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan [2] Department of Physics, Okayama University, Okayama 700-8530, Japan
| | - Minoru Nohara
- 1] The Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan [2] Department of Physics, Okayama University, Okayama 700-8530, Japan
| | - Kanta Ono
- Institute for Material Structure Science, High Energy Accelerator Research Organization, Tsukuba, Ibaraki 305-0801
| | - Hiroshi Kumigashira
- Institute for Material Structure Science, High Energy Accelerator Research Organization, Tsukuba, Ibaraki 305-0801
| | - Tomohiro Matsushita
- Japan Synchrotron Radiation Research Institute (JASRI)/SPring-8, 1-1-1 Kouto, Sayo, Hyogo 679-5198, Japan
| | - Masashi Arita
- Hiroshima Synchrotron Radiation Center, Hiroshima University, Higashi-Hiroshima, Hiroshima 739-0046, Japan
| | - Kenya Shimada
- Hiroshima Synchrotron Radiation Center, Hiroshima University, Higashi-Hiroshima, Hiroshima 739-0046, Japan
| | - Hirofumi Namatame
- Hiroshima Synchrotron Radiation Center, Hiroshima University, Higashi-Hiroshima, Hiroshima 739-0046, Japan
| | - Masaki Taniguchi
- Hiroshima Synchrotron Radiation Center, Hiroshima University, Higashi-Hiroshima, Hiroshima 739-0046, Japan
| | - Takanori Wakita
- 1] The Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan [2] Research Laboratory for Surface Science, Okayama University, 3-1-1 Tsushima-naka, Okayama 700-8530, Japan
| | - Yuji Muraoka
- 1] The Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan [2] Research Laboratory for Surface Science, Okayama University, 3-1-1 Tsushima-naka, Okayama 700-8530, Japan
| | - Takayoshi Yokoya
- 1] The Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan [2] Research Laboratory for Surface Science, Okayama University, 3-1-1 Tsushima-naka, Okayama 700-8530, Japan
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44
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Sakano M, Bahramy MS, Katayama A, Shimojima T, Murakawa H, Kaneko Y, Malaeb W, Shin S, Ono K, Kumigashira H, Arita R, Nagaosa N, Hwang HY, Tokura Y, Ishizaka K. Strongly spin-orbit coupled two-dimensional electron gas emerging near the surface of polar semiconductors. Phys Rev Lett 2013; 110:107204. [PMID: 23521291 DOI: 10.1103/physrevlett.110.107204] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/28/2012] [Indexed: 06/01/2023]
Abstract
We investigate the two-dimensional highly spin-polarized electron accumulation layers commonly appearing near the surface of n-type polar semiconductors BiTeX (X=I, Br, and Cl) by angular-resolved photoemission spectroscopy. Because of the polarity and the strong spin-orbit interaction built in the bulk atomic configurations, the quantized conduction-band subbands show giant Rashba-type spin splitting. The characteristic 2D confinement effect is clearly observed also in the valence bands down to the binding energy of 4 eV. The X-dependent Rashba spin-orbit coupling is directly estimated from the observed spin-split subbands, which roughly scales with the inverse of the band-gap size in BiTeX.
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Affiliation(s)
- M Sakano
- Department of Applied Physics, The University of Tokyo, Tokyo 113-8656, Japan
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Yokoya T, Yoshida R, Utsumi Y, Tsubota K, Okazaki H, Wakita T, Mizuguchi Y, Takano Y, Muro T, Kato Y, Kumigashira H, Oshima M, Harima H, Aiura Y, Sato H, Ino A, Namatame H, Taniguchi M, Hirai M, Muraoka Y. Te concentration dependent photoemission and inverse-photoemission study of FeSe 1-xTe x. Sci Technol Adv Mater 2012; 13:054403. [PMID: 27877521 PMCID: PMC5099622 DOI: 10.1088/1468-6996/13/5/054403] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/30/2012] [Accepted: 11/05/2012] [Indexed: 06/03/2023]
Abstract
We have characterized the electronic structure of FeSe1-x Te x for various x values using soft x-ray photoemission spectroscopy (SXPES), high-resolution photoemission spectroscopy (HRPES) and inverse photoemission spectroscopy (IPES). The SXPES valence band spectral shape shows that the 2 eV feature in FeSe, which was ascribed to the lower Hubbard band in previous theoretical studies, becomes less prominent with increasing x. HRPES exhibits systematic x dependence of the structure near the Fermi level (EF): its splitting near EF and filling of the pseudogap in FeSe. IPES shows two features, near EF and approximately 6 eV above EF; the former may be related to the Fe 3d states hybridized with chalcogenide p states, while the latter may consist of plane-wave-like and Se d components. In the incident electron energy dependence of IPES, the density of states near EF for FeSe and FeTe has the Fano lineshape characteristic of resonant behavior. These compounds exhibit different resonance profiles, which may reflect the differences in their electronic structures. By combining the PES and IPES data the on-site Coulomb energy was estimated at 3.5 eV for FeSe.
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Affiliation(s)
- Takayoshi Yokoya
- The Graduate School of Natural Science and Technology, Okayama University, 3-1-1 Tsushima-naka, Okayama 700-8530, Japan
- Japan Science and Technology Agency-Transformative Research Project on Iron Pnictides (JST-TRIP), Tsukuba, Ibaraki 305-0047, Japan
- Core Research for Evolutional Science and Technology (CREST) Japan Science and Technology Agency, Okayama 700-8530, Japan
- Research Laboratory for Surface Science, Okayama University, 3-1-1 Tsushima-naka, Okayama 700-8530, Japan
| | - Rikiya Yoshida
- The Graduate School of Natural Science and Technology, Okayama University, 3-1-1 Tsushima-naka, Okayama 700-8530, Japan
| | - Yuki Utsumi
- Graduate School of Science, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima 739-8526, Japan
| | - Koji Tsubota
- The Graduate School of Natural Science and Technology, Okayama University, 3-1-1 Tsushima-naka, Okayama 700-8530, Japan
| | - Hiroyuki Okazaki
- The Graduate School of Natural Science and Technology, Okayama University, 3-1-1 Tsushima-naka, Okayama 700-8530, Japan
- Core Research for Evolutional Science and Technology (CREST) Japan Science and Technology Agency, Okayama 700-8530, Japan
| | - Takanori Wakita
- The Graduate School of Natural Science and Technology, Okayama University, 3-1-1 Tsushima-naka, Okayama 700-8530, Japan
- Japan Science and Technology Agency-Transformative Research Project on Iron Pnictides (JST-TRIP), Tsukuba, Ibaraki 305-0047, Japan
- Core Research for Evolutional Science and Technology (CREST) Japan Science and Technology Agency, Okayama 700-8530, Japan
- Research Laboratory for Surface Science, Okayama University, 3-1-1 Tsushima-naka, Okayama 700-8530, Japan
| | - Yoshikazu Mizuguchi
- Japan Science and Technology Agency-Transformative Research Project on Iron Pnictides (JST-TRIP), Tsukuba, Ibaraki 305-0047, Japan
- National Institute for Materials Science, Tsukuba, Ibaraki 305-0047, Japan
- University of TsukubaGraduate School of Pure and Applied Sciences, Tsukuba, Ibaraki 305-8577, Japan
| | - Yoshihiko Takano
- Japan Science and Technology Agency-Transformative Research Project on Iron Pnictides (JST-TRIP), Tsukuba, Ibaraki 305-0047, Japan
- National Institute for Materials Science, Tsukuba, Ibaraki 305-0047, Japan
- University of TsukubaGraduate School of Pure and Applied Sciences, Tsukuba, Ibaraki 305-8577, Japan
| | - Takayuki Muro
- Japan Synchrotron Radiation Research Institute, Sayo, Hyogo 679-5198, Japan
| | - Yukako Kato
- Japan Synchrotron Radiation Research Institute, Sayo, Hyogo 679-5198, Japan
| | - Hiroshi Kumigashira
- Core Research for Evolutional Science and Technology (CREST) Japan Science and Technology Agency, Okayama 700-8530, Japan
- Department of Applied Chemistry, The University of Tokyo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - Masaharu Oshima
- Core Research for Evolutional Science and Technology (CREST) Japan Science and Technology Agency, Okayama 700-8530, Japan
- Department of Applied Chemistry, The University of Tokyo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - Hisatomo Harima
- Japan Science and Technology Agency-Transformative Research Project on Iron Pnictides (JST-TRIP), Tsukuba, Ibaraki 305-0047, Japan
- Department of Physics, Graduate School of Science, Kobe University, Kobe, Hyogo 657-8501, Japan
| | - Yoshihiro Aiura
- Japan Science and Technology Agency-Transformative Research Project on Iron Pnictides (JST-TRIP), Tsukuba, Ibaraki 305-0047, Japan
- National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki 305-8568, Japan
| | - Hitoshi Sato
- Japan Science and Technology Agency-Transformative Research Project on Iron Pnictides (JST-TRIP), Tsukuba, Ibaraki 305-0047, Japan
- Hiroshima Synchrotron Radiation Center, Hiroshima University, Higashihiroshima, Hiroshima 739-0046, Japan
| | - Akihiro Ino
- Japan Science and Technology Agency-Transformative Research Project on Iron Pnictides (JST-TRIP), Tsukuba, Ibaraki 305-0047, Japan
- Graduate School of Science, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima 739-8526, Japan
| | - Hirofumi Namatame
- Hiroshima Synchrotron Radiation Center, Hiroshima University, Higashihiroshima, Hiroshima 739-0046, Japan
| | - Masaki Taniguchi
- Graduate School of Science, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima 739-8526, Japan
- Hiroshima Synchrotron Radiation Center, Hiroshima University, Higashihiroshima, Hiroshima 739-0046, Japan
| | - Masaaki Hirai
- The Graduate School of Natural Science and Technology, Okayama University, 3-1-1 Tsushima-naka, Okayama 700-8530, Japan
- Japan Science and Technology Agency-Transformative Research Project on Iron Pnictides (JST-TRIP), Tsukuba, Ibaraki 305-0047, Japan
- Core Research for Evolutional Science and Technology (CREST) Japan Science and Technology Agency, Okayama 700-8530, Japan
- Research Laboratory for Surface Science, Okayama University, 3-1-1 Tsushima-naka, Okayama 700-8530, Japan
| | - Yuji Muraoka
- The Graduate School of Natural Science and Technology, Okayama University, 3-1-1 Tsushima-naka, Okayama 700-8530, Japan
- Japan Science and Technology Agency-Transformative Research Project on Iron Pnictides (JST-TRIP), Tsukuba, Ibaraki 305-0047, Japan
- Core Research for Evolutional Science and Technology (CREST) Japan Science and Technology Agency, Okayama 700-8530, Japan
- Research Laboratory for Surface Science, Okayama University, 3-1-1 Tsushima-naka, Okayama 700-8530, Japan
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Aizaki S, Yoshida T, Yoshimatsu K, Takizawa M, Minohara M, Ideta S, Fujimori A, Gupta K, Mahadevan P, Horiba K, Kumigashira H, Oshima M. Self-energy on the low- to high-energy electronic structure of correlated metal SrVO3. Phys Rev Lett 2012; 109:056401. [PMID: 23006190 DOI: 10.1103/physrevlett.109.056401] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/20/2011] [Indexed: 06/01/2023]
Abstract
The correlated electronic structure of SrVO(3) has been investigated by angle-resolved photoemission spectroscopy using in situ prepared thin films. Pronounced features of band renormalization have been observed: a sharp kink ∼60 meV below the Fermi level (E(F)) and a broad so-called "high-energy kink" ∼0.3 eV below E(F) as in the high-T(c) cuprates, although SrVO(3) does not show magnetic fluctuations. We have deduced the self-energy in a wide energy range by applying the Kramers-Kronig relation to the observed spectra. The obtained self-energy clearly shows a large energy scale of ∼0.7 eV, which is attributed to electron-electron interaction and gives rise to the ∼0.3 eV kink in the band dispersion as well as the incoherent peak ∼1.5 eV below E(F). The present analysis enables us to obtain a consistent picture for both the incoherent spectra and the band renormalization.
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Affiliation(s)
- S Aizaki
- Department of Physics, The University of Tokyo, Japan
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47
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Horiba K, Nakamura Y, Nagamura N, Toyoda S, Kumigashira H, Oshima M, Amemiya K, Senba Y, Ohashi H. Scanning photoelectron microscope for nanoscale three-dimensional spatial-resolved electron spectroscopy for chemical analysis. Rev Sci Instrum 2011; 82:113701. [PMID: 22128978 DOI: 10.1063/1.3657156] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
In order to achieve nondestructive observation of the three-dimensional spatially resolved electronic structure of solids, we have developed a scanning photoelectron microscope system with the capability of depth profiling in electron spectroscopy for chemical analysis (ESCA). We call this system 3D nano-ESCA. For focusing the x-ray, a Fresnel zone plate with a diameter of 200 μm and an outermost zone width of 35 nm is used. In order to obtain the angular dependence of the photoelectron spectra for the depth-profile analysis without rotating the sample, we adopted a modified VG Scienta R3000 analyzer with an acceptance angle of 60° as a high-resolution angle-resolved electron spectrometer. The system has been installed at the University-of-Tokyo Materials Science Outstation beamline, BL07LSU, at SPring-8. From the results of the line-scan profiles of the poly-Si/high-k gate patterns, we achieved a total spatial resolution better than 70 nm. The capability of our system for pinpoint depth-profile analysis and high-resolution chemical state analysis is demonstrated.
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Affiliation(s)
- K Horiba
- Department of Applied Chemistry, The University of Tokyo, Tokyo 113-8656, Japan.
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48
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Yoshimatsu K, Horiba K, Kumigashira H, Yoshida T, Fujimori A, Oshima M. Metallic Quantum Well States in Artificial Structures of Strongly Correlated Oxide. Science 2011; 333:319-22. [DOI: 10.1126/science.1205771] [Citation(s) in RCA: 120] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
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Maruyama S, Takeyama Y, Taniguchi H, Fukumoto H, Itoh M, Kumigashira H, Oshima M, Yamamoto T, Matsumoto Y. Molecular beam deposition of nanoscale ionic liquids in ultrahigh vacuum. ACS Nano 2010; 4:5946-52. [PMID: 20863104 DOI: 10.1021/nn101036v] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
We propose a new approach to nanoscience and technology for ionic liquids (ILs): molecular beam deposition of IL in ultrahigh vacuum by using a continuous wave infrared (CW-IR) laser deposition technique. This approach has made it possible to prepare a variety of "nano-IL" with the given composition on the substrate: a nanodroplet, on one hand, the volume of which goes down to 1 aL and, on the other hand, an ultrathin film with a thickness to several 100 nm or less. The result of fractional distillation of a binary mixture of ILs, investigated by nuclear magnetic resonance as well as electrospray ionization time-of-flight mass spectrometry, indicates that this deposition process is based on the thermal evaporation of ILs, and thus this process also can be used as a new purification method of ILs in vacuum. Furthermore, the fabrication of binary mixture droplets of two ILs on the substrate by alternating deposition of two ILs was demonstrated; the homogeneity of the composition was confirmed even for one single droplet by high-spatial-resolution Raman spectroscopy.
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Affiliation(s)
- Shingo Maruyama
- Materials and Structures Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503, Japan
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50
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Yoshimatsu K, Okabe T, Kumigashira H, Okamoto S, Aizaki S, Fujimori A, Oshima M. Dimensional-crossover-driven metal-insulator transition in SrVO3 ultrathin films. Phys Rev Lett 2010; 104:147601. [PMID: 20481962 DOI: 10.1103/physrevlett.104.147601] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/12/2009] [Indexed: 05/29/2023]
Abstract
We have investigated the changes occurring in the electronic structure of digitally controlled SrVO(3) ultrathin films across the metal-insulator transition (MIT) by the film thickness using in situ photoemission spectroscopy. With decreasing film thickness, a pseudogap is formed at E(F) through spectral weight transfer from the coherent part to the incoherent part. The pseudogap finally evolves into an energy gap that is indicative of the MIT in a SrVO(3) ultrathin film. The observed spectral behavior is reproduced by layer dynamical-mean-field-theory calculations, and it indicates that the observed MIT is caused by the reduction in the bandwidth due to the dimensional crossover.
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Affiliation(s)
- K Yoshimatsu
- Department of Applied Chemistry, University of Tokyo, Bunkyo-ku, Tokyo 113-8656, Japan
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