1
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Christensen DV, Steegemans TS, D Pomar T, Chen YZ, Smith A, Strocov VN, Kalisky B, Pryds N. Extreme magnetoresistance at high-mobility oxide heterointerfaces with dynamic defect tunability. Nat Commun 2024; 15:4249. [PMID: 38762504 PMCID: PMC11102559 DOI: 10.1038/s41467-024-48398-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2023] [Accepted: 04/30/2024] [Indexed: 05/20/2024] Open
Abstract
Magnetic field-induced changes in the electrical resistance of materials reveal insights into the fundamental properties governing their electronic and magnetic behavior. Various classes of magnetoresistance have been realized, including giant, colossal, and extraordinary magnetoresistance, each with distinct physical origins. In recent years, extreme magnetoresistance (XMR) has been observed in topological and non-topological materials displaying a non-saturating magnetoresistance reaching 103-108% in magnetic fields up to 60 T. XMR is often intimately linked to a gapless band structure with steep bands and charge compensation. Here, we show that a linear XMR of 80,000% at 15 T and 2 K emerges at the high-mobility interface between the large band-gap oxides γ-Al2O3 and SrTiO3. Despite the chemically and electronically very dissimilar environment, the temperature/field phase diagrams of γ-Al2O3/SrTiO3 bear a striking resemblance to XMR semimetals. By comparing magnetotransport, microscopic current imaging, and momentum-resolved band structures, we conclude that the XMR in γ-Al2O3/SrTiO3 is not strongly linked to the band structure, but arises from weak disorder enforcing a squeezed guiding center motion of electrons. We also present a dynamic XMR self-enhancement through an autonomous redistribution of quasi-mobile oxygen vacancies. Our findings shed new light on XMR and introduce tunability using dynamic defect engineering.
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Affiliation(s)
- D V Christensen
- Department of Energy Conversion and Storage, Technical University of Denmark, DK-2800, Kongens Lyngby, Denmark.
| | - T S Steegemans
- Department of Energy Conversion and Storage, Technical University of Denmark, DK-2800, Kongens Lyngby, Denmark
| | - T D Pomar
- Department of Energy Conversion and Storage, Technical University of Denmark, DK-2800, Kongens Lyngby, Denmark
| | - Y Z Chen
- Department of Energy Conversion and Storage, Technical University of Denmark, DK-2800, Kongens Lyngby, Denmark
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
| | - A Smith
- Department of Energy Conversion and Storage, Technical University of Denmark, DK-2800, Kongens Lyngby, Denmark
| | - V N Strocov
- Swiss Light Source, Paul Scherrer Institute, 5232, Villigen-PSI, Switzerland
| | - B Kalisky
- Department of Physics and Institute of Nanotechnology and Advanced Materials, Bar-Ilan University, Ramat-Gan, 5290002, Israel
| | - N Pryds
- Department of Energy Conversion and Storage, Technical University of Denmark, DK-2800, Kongens Lyngby, Denmark
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2
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Caputo M, Studniarek M, Guedes EB, Schio L, Baiseitov K, Daffé N, Bachellier N, Chikina A, Di Santo G, Verdini A, Goldoni A, Muntwiler M, Piamonteze C, Floreano L, Radovic M, Dreiser J. Charge Transfer and Orbital Reconstruction at an Organic-Oxide Interface. NANO LETTERS 2023. [PMID: 38029285 DOI: 10.1021/acs.nanolett.3c03713] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/01/2023]
Abstract
The two-dimensional electron system (2DES) located at the surface of strontium titanate (STO) and at several other STO-based interfaces has been an established platform for the study of novel physical phenomena since its discovery. Here we report how the interfacing of STO and tetracyanoquinodimethane (TCNQ) results in a charge transfer that depletes the number of free carriers at the STO surface, with a strong impact on its electronic structure. Our study paves the way for efficient tuning of the electronic properties, which promises novel applications in the framework of oxide/organic-based electronics.
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Affiliation(s)
- Marco Caputo
- Elettra Sincrotrone Trieste, s.s. 14 km 163.5 in Area Science Park, 34149 Trieste, Italy
- MAX IV Laboratory, Lund University, PO Box 118, 22100 Lund, Sweden
| | - Michał Studniarek
- Swiss Light Source, Paul Scherrer Institut, Forschungsstrasse 111, 5232 Villigen PSI, Switzerland
| | - Eduardo Bonini Guedes
- Swiss Light Source, Paul Scherrer Institut, Forschungsstrasse 111, 5232 Villigen PSI, Switzerland
| | - Luca Schio
- Laboratorio TASC, Istituto Officina dei Materiali (IOM)-CNR, Area Science Park, S.S. 14 km 163.5, 34149 Trieste, Italy
| | - Kassymkhan Baiseitov
- Swiss Light Source, Paul Scherrer Institut, Forschungsstrasse 111, 5232 Villigen PSI, Switzerland
| | - Niéli Daffé
- Swiss Light Source, Paul Scherrer Institut, Forschungsstrasse 111, 5232 Villigen PSI, Switzerland
| | - Nicolas Bachellier
- Swiss Light Source, Paul Scherrer Institut, Forschungsstrasse 111, 5232 Villigen PSI, Switzerland
| | - Alla Chikina
- Swiss Light Source, Paul Scherrer Institut, Forschungsstrasse 111, 5232 Villigen PSI, Switzerland
| | - Giovanni Di Santo
- Elettra Sincrotrone Trieste, s.s. 14 km 163.5 in Area Science Park, 34149 Trieste, Italy
| | - Alberto Verdini
- Laboratorio TASC, Istituto Officina dei Materiali (IOM)-CNR, Area Science Park, S.S. 14 km 163.5, 34149 Trieste, Italy
| | - Andrea Goldoni
- Elettra Sincrotrone Trieste, s.s. 14 km 163.5 in Area Science Park, 34149 Trieste, Italy
| | - Matthias Muntwiler
- Swiss Light Source, Paul Scherrer Institut, Forschungsstrasse 111, 5232 Villigen PSI, Switzerland
| | - Cinthia Piamonteze
- Swiss Light Source, Paul Scherrer Institut, Forschungsstrasse 111, 5232 Villigen PSI, Switzerland
| | - Luca Floreano
- Laboratorio TASC, Istituto Officina dei Materiali (IOM)-CNR, Area Science Park, S.S. 14 km 163.5, 34149 Trieste, Italy
| | - Milan Radovic
- Swiss Light Source, Paul Scherrer Institut, Forschungsstrasse 111, 5232 Villigen PSI, Switzerland
| | - Jan Dreiser
- Swiss Light Source, Paul Scherrer Institut, Forschungsstrasse 111, 5232 Villigen PSI, Switzerland
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3
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Li H, Gan Y, Husanu MA, Dahm RT, Christensen DV, Radovic M, Sun J, Shi M, Shen B, Pryds N, Chen Y. Robust Electronic Structure of Manganite-Buffered Oxide Interfaces with Extreme Mobility Enhancement. ACS NANO 2022; 16:6437-6443. [PMID: 35312282 DOI: 10.1021/acsnano.2c00609] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
The electronic structure as well as the mechanism underlying the high-mobility two-dimensional electron gases (2DEGs) at complex oxide interfaces remain elusive. Herein, using soft X-ray angle-resolved photoemission spectroscopy (ARPES), we present the band dispersion of metallic states at buffered LaAlO3/SrTiO3 (LAO/STO) heterointerfaces where a single-unit-cell LaMnO3 (LMO) spacer not only enhances the electron mobility but also renders the electronic structure robust toward X-ray radiation. By tracing the evolution of band dispersion, orbital occupation, and electron-phonon interaction of the interfacial 2DEG, we find unambiguous evidence that the insertion of the LMO buffer strongly suppresses both the formation of oxygen vacancies as well as the electron-phonon interaction on the STO side. The latter effect makes the buffered sample different from any other STO-based interfaces and may explain the maximum mobility enhancement achieved at buffered oxide interfaces.
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Affiliation(s)
- Hang Li
- Department of Energy Conversion and Storage, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark
- Swiss Light Source, Paul Scherrer Institute, 5232 Villigen, PSI, Switzerland
| | - Yulin Gan
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, 100190 Beijing, China
| | - Marius-Adrian Husanu
- National Institute of Materials Physics, Atomistilor 405A, 077125 Magurele, Romania
| | - Rasmus Tindal Dahm
- Department of Energy Conversion and Storage, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark
| | | | - Milan Radovic
- Swiss Light Source, Paul Scherrer Institute, 5232 Villigen, PSI, Switzerland
| | - Jirong Sun
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, 100190 Beijing, China
| | - Ming Shi
- Swiss Light Source, Paul Scherrer Institute, 5232 Villigen, PSI, Switzerland
| | - Baogen Shen
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, 100190 Beijing, China
| | - Nini Pryds
- Department of Energy Conversion and Storage, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark
| | - Yunzhong Chen
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, 100190 Beijing, China
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4
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Chiu CC, Ho SZ, Lee JM, Shao YC, Shen Y, Liu YC, Chang YW, Zheng YZ, Huang R, Chang CF, Kuo CY, Duan CG, Huang SW, Yang JC, Chuang YD. Presence of Delocalized Ti 3d Electrons in Ultrathin Single-Crystal SrTiO 3. NANO LETTERS 2022; 22:1580-1586. [PMID: 35073104 DOI: 10.1021/acs.nanolett.1c04434] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Strontium titanate (STO), with a wide spectrum of emergent properties such as ferroelectricity and superconductivity, has received significant attention in the community of strongly correlated materials. In the strain-free STO film grown on the SrRuO3 buffer layer, the existing polar nanoregions can facilitate room-temperature ferroelectricity when the STO film thickness approaches 10 nm. Here we show that around this thickness scale, the freestanding STO films without the influence of a substrate show the tetragonal structure at room temperature, contrasting with the cubic structure seen in bulk form. The spectroscopic measurements reveal the modified Ti-O orbital hybridization that causes the Ti ion to deviate from its nominal 4+ valency (3d0 configuration) with excess delocalized 3d electrons. Additionally, the Ti ion in TiO6 octahedron exhibits an off-center displacement. The inherent symmetry lowering in ultrathin freestanding films offers an alternative way to achieve tunable electronic structures that are of paramount importance for future technological applications.
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Affiliation(s)
- Chun-Chien Chiu
- Department of Physics, National Cheng Kung University, Tainan 701, Taiwan
| | - Sheng-Zhu Ho
- Department of Physics, National Cheng Kung University, Tainan 701, Taiwan
| | - Jenn-Min Lee
- MAX IV Laboratory, Lund University, P.O. Box 118, 221 00 Lund, Sweden
| | - Yu-Cheng Shao
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
- National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan
| | - Yang Shen
- Key Laboratory of Polar Materials and Devices, Ministry of Education, Department of Electronics, East China Normal University, Shanghai 200241, China
| | - Yu-Chen Liu
- Department of Physics, National Cheng Kung University, Tainan 701, Taiwan
| | - Yao-Wen Chang
- Department of Physics, National Cheng Kung University, Tainan 701, Taiwan
| | - Yun-Zhe Zheng
- Key Laboratory of Polar Materials and Devices, Ministry of Education, Department of Electronics, East China Normal University, Shanghai 200241, China
| | - Rong Huang
- Key Laboratory of Polar Materials and Devices, Ministry of Education, Department of Electronics, East China Normal University, Shanghai 200241, China
| | - Chun-Fu Chang
- Max-Planck Institute for Chemical Physics of Solids, Dresden 01187, Germany
| | - Chang-Yang Kuo
- National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan
- Department of Electrophysics, National Chiao Tung University, Hsinchu 30010, Taiwan
| | - Chun-Gang Duan
- Key Laboratory of Polar Materials and Devices, Ministry of Education, Department of Electronics, East China Normal University, Shanghai 200241, China
| | - Shih-Wen Huang
- MAX IV Laboratory, Lund University, P.O. Box 118, 221 00 Lund, Sweden
- Swiss Light Source, Paul Scherrer Institut, CH5232 Villigen PSI, Switzerland
| | - Jan-Chi Yang
- Department of Physics, National Cheng Kung University, Tainan 701, Taiwan
- Center for Quantum Frontiers of Research & Technology (QFort), National Cheng Kung University, Tainan 70101, Taiwan
| | - Yi-De Chuang
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
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5
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Mallik S, Ménard GC, Saïz G, Gilmutdinov I, Vignolles D, Proust C, Gloter A, Bergeal N, Gabay M, Bibes M. From Low-Field Sondheimer Oscillations to High-Field Very Large and Linear Magnetoresistance in a SrTiO 3-Based Two-Dimensional Electron Gas. NANO LETTERS 2022; 22:65-72. [PMID: 34914397 DOI: 10.1021/acs.nanolett.1c03198] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Quantum materials harbor a cornucopia of exotic transport phenomena challenging our understanding of condensed matter. Among these, a giant, nonsaturating linear magnetoresistance (MR) has been reported in various systems, from Weyl semimetals to topological insulators. Its origin is often ascribed to unusual band structure effects, but it may also be caused by extrinsic sample disorder. Here, we report a very large linear MR in a SrTiO3 two-dimensional electron gas and, by combining transport measurements with electron spectromicroscopy, show that it is caused by nanoscale inhomogeneities that are self-organized during sample growth. Our data also reveal semiclassical Sondheimer oscillations arising from interferences between helicoidal electron trajectories, from which we determine the 2DEG thickness. Our results bring insight into the origin of linear MR in quantum materials, expand the range of functionalities of oxide 2DEGs, and suggest exciting routes to explore the interaction of linear MR with features like Rashba spin-orbit coupling.
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Affiliation(s)
- Srijani Mallik
- Unité Mixte de Physique, CNRS, Thales, Université Paris-Saclay, 1 Avenue Augustin Fresnel, 91767 Palaiseau, France
| | - Gerbold C Ménard
- Laboratoire de Physique et d'Etude des Matériaux, ESPCI Paris, PSL University, CNRS, Sorbonne Université, 75005 Paris, France
| | - Guilhem Saïz
- Laboratoire de Physique et d'Etude des Matériaux, ESPCI Paris, PSL University, CNRS, Sorbonne Université, 75005 Paris, France
| | - Ildar Gilmutdinov
- LNCMI-EMFL, CNRS, Université Grenoble Alpes, INSA-T, UPS, 31400 Toulouse, France
| | - David Vignolles
- LNCMI-EMFL, CNRS, Université Grenoble Alpes, INSA-T, UPS, 31400 Toulouse, France
| | - Cyril Proust
- LNCMI-EMFL, CNRS, Université Grenoble Alpes, INSA-T, UPS, 31400 Toulouse, France
| | - Alexandre Gloter
- Laboratoire de Physique des Solides, Université Paris-Saclay, CNRS UMR 8502, 91405 Orsay, France
| | - Nicolas Bergeal
- Laboratoire de Physique et d'Etude des Matériaux, ESPCI Paris, PSL University, CNRS, Sorbonne Université, 75005 Paris, France
| | - Marc Gabay
- Laboratoire de Physique des Solides, Université Paris-Saclay, CNRS UMR 8502, 91405 Orsay, France
| | - Manuel Bibes
- Unité Mixte de Physique, CNRS, Thales, Université Paris-Saclay, 1 Avenue Augustin Fresnel, 91767 Palaiseau, France
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6
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Guedes EB, Muff S, Brito WH, Caputo M, Li H, Plumb NC, Dil JH, Radović M. Universal Structural Influence on the 2D Electron Gas at SrTiO 3 Surfaces. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2021; 8:e2100602. [PMID: 34532983 PMCID: PMC8596100 DOI: 10.1002/advs.202100602] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/16/2021] [Revised: 06/23/2021] [Indexed: 05/28/2023]
Abstract
The 2-dimensional electron gas (2DEG) found at the surface of SrTiO3 and related interfaces has attracted significant attention as a promising basis for oxide electronics. In order to utilize its full potential, the response of this 2DEG to structural changes and surface modification must be understood in detail. Here, a study of the detailed electronic structure evolution of the 2DEG as a function of sample temperature and surface step density is presented. By comparing the experimental results with ab initio calculations, it is shown that local structure relaxations cause a metal-insulator transition of the system around 135 K. This study presents a new and simple way of tuning the 2DEG via surface vicinality and identifies how the operation of prospective devices will respond to changes in temperature.
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Affiliation(s)
- Eduardo B. Guedes
- Photon Science DivisionPaul Scherrer InstitutVilligenCH‐5232Switzerland
| | - Stefan Muff
- Photon Science DivisionPaul Scherrer InstitutVilligenCH‐5232Switzerland
| | - Walber H. Brito
- Departamento de FísicaUniversidade Federal de Minas GeraisC.P. 702Belo HorizonteMinas Gerais30123Brazil
| | - Marco Caputo
- Photon Science DivisionPaul Scherrer InstitutVilligenCH‐5232Switzerland
- Elettra‐Sincrotrone TriesteS.C.p.A, S.S 14‐km 163.5 in AREA Science Park, BasovizzaTrieste34149Italy
| | - Hang Li
- Photon Science DivisionPaul Scherrer InstitutVilligenCH‐5232Switzerland
- Department of Energy Conversion and StorageTechnical University of DenmarkKgs. Lyngby2800Denmark
| | - Nicholas C. Plumb
- Photon Science DivisionPaul Scherrer InstitutVilligenCH‐5232Switzerland
| | - J. Hugo Dil
- Photon Science DivisionPaul Scherrer InstitutVilligenCH‐5232Switzerland
- Institut de PhysiqueÉcole Polytechnique Fédérale de LausanneLausanneCH‐1015Switzerland
| | - Milan Radović
- Photon Science DivisionPaul Scherrer InstitutVilligenCH‐5232Switzerland
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7
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Chikina A, Christensen DV, Borisov V, Husanu MA, Chen Y, Wang X, Schmitt T, Radovic M, Nagaosa N, Mishchenko AS, Valentí R, Pryds N, Strocov VN. Band-Order Anomaly at the γ-Al 2O 3/SrTiO 3 Interface Drives the Electron-Mobility Boost. ACS NANO 2021; 15:4347-4356. [PMID: 33661601 DOI: 10.1021/acsnano.0c07609] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
The rich functionalities of transition-metal oxides and their interfaces bear an enormous technological potential. Its realization in practical devices requires, however, a significant improvement of yet relatively low electron mobility in oxide materials. Recently, a mobility boost of about 2 orders of magnitude has been demonstrated at the spinel-perovskite γ-Al2O3/SrTiO3 interface compared to the paradigm perovskite-perovskite LaAlO3/SrTiO3 interface. We explore the fundamental physics behind this phenomenon from direct measurements of the momentum-resolved electronic structure of this interface using resonant soft-X-ray angle-resolved photoemission. We find an anomaly in orbital ordering of the mobile electrons in γ-Al2O3/SrTiO3 which depopulates electron states in the top SrTiO3 layer. This rearrangement of the mobile electron system pushes the electron density away from the interface, which reduces its overlap with the interfacial defects and weakens the electron-phonon interaction, both effects contributing to the mobility boost. A crystal-field analysis shows that the band order alters owing to the symmetry breaking between the spinel γ-Al2O3 and perovskite SrTiO3. Band-order engineering, exploiting the fundamental symmetry properties, emerges as another route to boost the performance of oxide devices.
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Affiliation(s)
- Alla Chikina
- Swiss Light Source, Paul Scherrer Institute, 5232 Villigen-PSI, Switzerland
- Institute of Physics and Astronomy, Aarhus University, Ny Munkegade 120, 8000 Aarhus, Denmark
| | - Dennis V Christensen
- Department of Energy Conversion and Storage, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark
| | - Vladislav Borisov
- Institut für Theoretische Physik, Goethe-Universität Frankfurt am Main, Max-von-Laue-Strasse 1, 60438 Frankfurt am Main, Germany
- Department of Physics and Astronomy, Uppsala University, Box 516, 5120 Uppsala, Sweden
| | - Marius-Adrian Husanu
- Swiss Light Source, Paul Scherrer Institute, 5232 Villigen-PSI, Switzerland
- National Institute of Materials Physics, Atomistilor 405A, 077125 Magurele, Romania
| | - Yunzhong Chen
- Department of Energy Conversion and Storage, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Xiaoqiang Wang
- Swiss Light Source, Paul Scherrer Institute, 5232 Villigen-PSI, Switzerland
| | - Thorsten Schmitt
- Swiss Light Source, Paul Scherrer Institute, 5232 Villigen-PSI, Switzerland
| | - Milan Radovic
- Swiss Light Source, Paul Scherrer Institute, 5232 Villigen-PSI, Switzerland
| | - Naoto Nagaosa
- RIKEN Center for Emergent Matter Science, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
- Department of Applied Physics, University of Tokyo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - Andrey S Mishchenko
- RIKEN Center for Emergent Matter Science, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - Roser Valentí
- Institut für Theoretische Physik, Goethe-Universität Frankfurt am Main, Max-von-Laue-Strasse 1, 60438 Frankfurt am Main, Germany
| | - Nini Pryds
- Department of Energy Conversion and Storage, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark
| | - Vladimir N Strocov
- Swiss Light Source, Paul Scherrer Institute, 5232 Villigen-PSI, Switzerland
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8
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Kataoka N, Tanaka M, Hosoda W, Taniguchi T, Fujimori SI, Wakita T, Muraoka Y, Yokoya T. Soft x-ray irradiation induced metallization of layered TiNCl. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2020; 33:035501. [PMID: 32977314 DOI: 10.1088/1361-648x/abbbc3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/11/2020] [Accepted: 09/25/2020] [Indexed: 06/11/2023]
Abstract
We have performed soft x-ray spectroscopy in order to study the photoirradiation time dependence of the valence band structure and chemical states of layered transition metal nitride chloride TiNCl. Under the soft x-ray irradiation, the intensities of the states near the Fermi level (EF) and the Ti3+component increased, while the Cl 2pintensity decreased. Ti 2p-3dresonance photoemission spectroscopy confirmed a distinctive Fermi edge with Ti 3dcharacter. These results indicate the photo-induced metallization originates from deintercalation due to Cl desorption, and thus provide a new carrier doping method that controls the conducting properties of TiNCl.
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Affiliation(s)
- Noriyuki Kataoka
- Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan
| | - Masashi Tanaka
- Graduate School of Engineering, Kyushu Institute of Technology, Kitakyushu 804-8550, Japan
| | - Wataru Hosoda
- Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan
| | - Takumi Taniguchi
- Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan
| | - Shin-Ichi Fujimori
- Materials Sciences Research Center, Japan Atomic Energy Agency, Sayo, Hyogo 679-5148, Japan
| | - Takanori Wakita
- Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan
- Research Institute for Interdisciplinary Science, Okayama University, Okayama 700-8530, 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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9
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Jovic V, Moser S, Papadogianni A, Koch RJ, Rossi A, Jozwiak C, Bostwick A, Rotenberg E, Kennedy JV, Bierwagen O, Smith KE. The Itinerant 2D Electron Gas of the Indium Oxide (111) Surface: Implications for Carbon- and Energy-Conversion Applications. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2020; 16:e1903321. [PMID: 31489781 DOI: 10.1002/smll.201903321] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/26/2019] [Revised: 08/09/2019] [Indexed: 06/10/2023]
Abstract
Transparent conducting oxides (TCO) have integral and emerging roles in photovoltaic, thermoelectric energy conversion, and more recently, photocatalytic systems. The functional properties of TCOs, and thus their role in these applications, are often mediated by the bulk electronic band structure but are also strongly influenced by the electronic structure of the native surface 2D electron gas (2DEG), particularly under operating conditions. This study investigates the 2DEG, and its response to changes in chemistry, at the (111) surface of the model TCO In2 O3 , through angle resolved and core level X-ray photoemission spectroscopy. It is found that the itinerant charge carriers of the 2DEG reside in two quantum well subbands penetrating up to 65 Å below the surface. The charge carrier concentration of this 2DEG, and thus the high surface n-type conductivity, emerges from donor-type oxygen vacancies of surface character and proves to be remarkably robust against surface absorbents and contamination. The optical transparency, however, may rely on the presence of ubiquitous surface adsorbed oxygen groups and hydrogen defect states that passivate localized oxygen vacancy states in the bandgap of In2 O3 .
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Affiliation(s)
- Vedran Jovic
- National Isotope Center, GNS Science, MacDiarmid Institute for Advanced Materials and Nanotechnology, Lower Hutt, Wellington, 5010, New Zealand
- School of Chemical Sciences, The University of Auckland, Auckland, 1010, New Zealand
| | - Simon Moser
- Physikalisches Institut, Universität Würzburg, Würzburg, D-97074, Germany
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
| | - Alexandra Papadogianni
- Paul-Drude-Institut für Festkörperelektronik, Leibniz-Institut im Forschungsverbund Berlin e.V., Hausvogteiplatz 5-7, Berlin, 10117, Germany
| | - Roland J Koch
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
| | - Antonio Rossi
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
- Department of Physics, University of California, Davis, CA, 95616, USA
| | - Chris Jozwiak
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
| | - Aaron Bostwick
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
| | - Eli Rotenberg
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
| | - John V Kennedy
- National Isotope Center, GNS Science, MacDiarmid Institute for Advanced Materials and Nanotechnology, Lower Hutt, Wellington, 5010, New Zealand
| | - Oliver Bierwagen
- Paul-Drude-Institut für Festkörperelektronik, Leibniz-Institut im Forschungsverbund Berlin e.V., Hausvogteiplatz 5-7, Berlin, 10117, Germany
| | - Kevin E Smith
- Department of Physics, Boston University, Boston, MA, 02215, USA
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10
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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] [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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11
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Mathieu C, Gonzalez S, Lubin C, Copie O, Feyer V, Schneider CM, Barrett N. High-temperature 2D Fermi surface of SrTiO3
studied by energy-filtered PEEM. SURF INTERFACE ANAL 2018. [DOI: 10.1002/sia.6533] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Claire Mathieu
- SPEC, CEA, CNRS; Université Paris-Saclay, CEA Saclay; Gif-sur-Yvette Cedex France
| | - Sara Gonzalez
- SPEC, CEA, CNRS; Université Paris-Saclay, CEA Saclay; Gif-sur-Yvette Cedex France
- BaDElPh beamline; Elettra-Sincrotrone Trieste; S.S. 14 km 163.5 in AREA Science Park Basovizza I-34149 Trieste Italy
| | - Christophe Lubin
- SPEC, CEA, CNRS; Université Paris-Saclay, CEA Saclay; Gif-sur-Yvette Cedex France
| | - Olivier Copie
- Institut Jean Lamour; UMR 7198 CNRS/Université de Lorraine; Vandoeuvre-lès-Nancy France
| | - Vitaliy Feyer
- Peter Grünberg Institute (PGI-6); JARA-FIT, Research Center Jülich; Jülich Germany
- NanoESCA beamline; Elettra-Sincrotrone Trieste; S.S. 14 km 163.5 in AREA Science Park Basovizza I-34149 Trieste Italy
| | - Claus M. Schneider
- Peter Grünberg Institute (PGI-6); JARA-FIT, Research Center Jülich; Jülich Germany
| | - Nick Barrett
- SPEC, CEA, CNRS; Université Paris-Saclay, CEA Saclay; Gif-sur-Yvette Cedex France
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12
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Mechanical dissipation from charge and spin transitions in oxygen-deficient SrTiO 3 surfaces. Nat Commun 2018; 9:2946. [PMID: 30054477 PMCID: PMC6063934 DOI: 10.1038/s41467-018-05392-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2018] [Accepted: 06/26/2018] [Indexed: 11/15/2022] Open
Abstract
Bodies in relative motion separated by a gap of a few nanometers can experience a tiny friction force. This non-contact dissipation can have various origins and can be successfully measured by a sensitive pendulum atomic force microscope tip oscillating laterally above the surface. Here, we report on the observation of dissipation peaks at selected voltage-dependent tip-surface distances for oxygen-deficient strontium titanate (SrTiO3) surface at low temperatures (T = 5 K). The observed dissipation peaks are attributed to tip-induced charge and spin state transitions in quantum-dot-like entities formed by single oxygen vacancies (and clusters thereof, possibly through a collective mechanism) at the SrTiO3 surface, which in view of technological and fundamental research relevance of the material opens important avenues for further studies and applications. Non-contact atomic force microscope (AFM) dissipation contains rich information on the electron, phonon and spin states, but has been poorly understood. Here the authors demonstrated that tip-induced charge and spin state transitions in oxygen vacancies at SrTiO3 surface are revealed by AFM dissipation measurements.
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13
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Sopiha KV, Malyi OI, Persson C, Wu P. Suppression of surfaces states at cubic perovskite (001) surfaces by CO 2 adsorption. Phys Chem Chem Phys 2018; 20:18828-18836. [PMID: 29964284 DOI: 10.1039/c8cp02535e] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
By using first-principles approach, the interaction of CO2 with (001) surfaces of six cubic ABO3 perovskites (A = Ba, Sr and B = Ti, Zr, Hf) is studied in detail. We show that CO2 adsorption results in the formation of highly stable CO3-like complexes with similar geometries for all investigated compounds. This reaction leads to the suppression of the surfaces states, opening the band gaps of the slab systems up to the corresponding bulk energy limits. For most AO-terminated ABO3(001) perovskite surfaces, a CO2 coverage of 0.25 was found to be sufficient to fully suppress the surface states, whereas the same effect can only be achieved at 0.50 CO2 coverage for the BO2-terminated surfaces. The largest band gap modulation among the AO-terminated surfaces was found for SrHfO3(001) and BaHfO3(001), whereas the most profound effect among the BO2-terminated surfaces was identified for SrTiO3(001) and BaTiO3(001). Based on these results and considering practical difficulties associated with measuring conductivity of highly resistive materials, TiO2-terminated SrTiO3(001) and BaTiO3(001) were identified as the most prospective candidates for chemiresistive CO2 sensing applications.
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Affiliation(s)
- Kostiantyn V Sopiha
- Entropic Interface Group, Engineering Product Development, Singapore University of Technology and Design, 8 Somapah Road, 487372 Singapore, Singapore.
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14
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Aschaffenburg DJ, Chen X, Cuk T. Faradaic oxygen evolution from SrTiO 3 under nano- and femto-second pulsed light excitation. Chem Commun (Camb) 2018; 53:7254-7257. [PMID: 28660920 DOI: 10.1039/c7cc03061d] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
During photocatalytic water oxidation, n-SrTiO3(100) demonstrated near 100% Faradaic efficiency for O2 evolution with nano- (30 ns) and femto- (150 fs) second pulsed laser excitation of the band gap, despite surface rearrangements attributed to the high peak power (300 MW cm-2). Therefore, these results establish a methodology for tracking intermediates of the water oxidation cycle at the n-SrTiO3(100) surface from the picosecond time scales of charge transfer through to the millisecond time scales of O2 evolution.
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Affiliation(s)
- D J Aschaffenburg
- Department of Chemistry, University of California, Berkeley, Berkeley, California 94720, USA
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15
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Sopiha KV, Malyi OI, Persson C, Wu P. Band gap modulation of SrTiO 3 upon CO 2 adsorption. Phys Chem Chem Phys 2018; 19:16629-16637. [PMID: 28620658 DOI: 10.1039/c7cp01462g] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Herein, CO2 chemisorption on SrTiO3(001) surfaces is studied using ab initio calculations to establish new chemical sensing mechanisms. It was found that CO2 adsorption opens the band gap of the material. However, the mechanisms are different: the CO2 adsorption on the TiO2-terminated surface neutralizes the surface states at the valence band (VB) maximum, whereas for the SrO-terminated surface it suppresses the conduction band (CB) minimum. For the TiO2-terminated surface, the effect is explained by the passivation of dangling bonds, whereas for the SrO-terminated surface, the suppression is caused by surface relaxation. Modulation of the VB states implies a more direct change in charge distribution, and thus, the induced change in the band gap is more prominent at the TiO2 termination. Further, it has been shown that both CO2 adsorption energy and surface band gap are strongly dependent on CO2 coverage, suggesting that the observed effect can be utilized in sensing applications for a wide range of CO2 concentrations.
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Affiliation(s)
- Kostiantyn V Sopiha
- Engineering Product Development, Singapore University of Technology and Design, 8 Somapah Road, 487372 Singapore, Singapore.
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16
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Electrons and Polarons at Oxide Interfaces Explored by Soft-X-Ray ARPES. SPECTROSCOPY OF COMPLEX OXIDE INTERFACES 2018. [DOI: 10.1007/978-3-319-74989-1_6] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
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17
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Zhou F, Liu Y, Lai Z, Liao M, Zhou Y, Huang Y, Zhu J. Quantum confined two-dimensional electron/hole gas switching by facet orientation of perovskite oxides. RSC Adv 2018; 8:20477-20482. [PMID: 35542364 PMCID: PMC9080832 DOI: 10.1039/c8ra03928c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2018] [Accepted: 05/29/2018] [Indexed: 11/21/2022] Open
Abstract
The Polar discontinuity at heterointerface and the bare surface reconstructs the electronic phase of perovskite oxides.
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Affiliation(s)
- Fei Zhou
- School of Materials Science and Engineering
- Harbin Institute of Technology
- Harbin
- China
- MIIT Key Laboratory of Critical Materials Technology for New Energy Conversion and Storage
| | - Yong Liu
- School of Materials Science and Engineering
- Harbin Institute of Technology
- Harbin
- China
- National Key Laboratory for Precision Hot Processing of Metals
| | - Zhonghong Lai
- Analysis and Testing Center
- Harbin Institute of Technology
- Harbin
- China
| | - Mingqing Liao
- School of Materials Science and Engineering
- Harbin Institute of Technology
- Harbin
- China
| | - Yi Zhou
- School of Materials Science and Engineering
- Harbin Institute of Technology
- Harbin
- China
| | - Yudong Huang
- MIIT Key Laboratory of Critical Materials Technology for New Energy Conversion and Storage
- School of Chemistry and Chemical Engineering, Harbin Institute of Technology
- Harbin
- China
| | - Jingchuan Zhu
- School of Materials Science and Engineering
- Harbin Institute of Technology
- Harbin
- China
- National Key Laboratory of Science and Technology on Advanced Composites in Special Environments
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18
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Ikegami H, Kim K, Sato D, Kono K, Choi H, Monarkha YP. Anomalous Quasiparticle Reflection from the Surface of a ^{3}He-^{4}He Dilute Solution. PHYSICAL REVIEW LETTERS 2017; 119:195302. [PMID: 29219484 DOI: 10.1103/physrevlett.119.195302] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/31/2017] [Indexed: 06/07/2023]
Abstract
A free surface of a dilute ^{3}He-^{4}He liquid mixture is a unique system where two Fermi liquids with distinct dimensions coexist: a three-dimensional (3D) ^{3}He Fermi liquid in the bulk and a two-dimensional (2D) ^{3}He Fermi liquid at the surface. To investigate a novel effect generated by the interaction between the two Fermi liquids, the mobility of a Wigner crystal of electrons formed on the free surface of the mixture is studied. An anomalous enhancement of the mobility, compared with the case where the 3D and 2D systems do not interact with each other, is observed. The enhancement is explained by the nontrivial reflection of 3D quasiparticles from the surface covered with the 2D ^{3}He system.
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Affiliation(s)
- Hiroki Ikegami
- RIKEN Center for Emergent Matter Science (CEMS), Wako, Saitama 351-0198, Japan
| | - Kitak Kim
- Department of Physics, KAIST, Daejeon 34141, Republic of Korea
| | - Daisuke Sato
- RIKEN Center for Emergent Matter Science (CEMS), Wako, Saitama 351-0198, Japan
| | - Kimitoshi Kono
- RIKEN Center for Emergent Matter Science (CEMS), Wako, Saitama 351-0198, Japan
| | - Hyoungsoon Choi
- Department of Physics, KAIST, Daejeon 34141, Republic of Korea
| | - Yuriy P Monarkha
- Institute for Low Temperature Physics and Engineering, 47 Nauky Avenue, Kharkov 61103, Ukraine
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19
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Plumb NC, Radović M. Angle-resolved photoemission spectroscopy studies of metallic surface and interface states of oxide insulators. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2017; 29:433005. [PMID: 28961143 DOI: 10.1088/1361-648x/aa833f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Over the last decade, conducting states embedded in insulating transition metal oxides (TMOs) have served as gateways to discovering and probing surprising phenomena that can emerge in complex oxides, while also opening opportunities for engineering advanced devices. These states are commonly realized at thin film interfaces, such as the well-known case of LaAlO3 (LAO) grown on SrTiO3 (STO). In recent years, the use of angle-resolved photoemission spectroscopy (ARPES) to investigate the k-space electronic structure of such materials led to the discovery that metallic states can also be formed on the bare surfaces of certain TMOs. In this topical review, we report on recent studies of low-dimensional metallic states confined at insulating oxide surfaces and interfaces as seen from the perspective of ARPES, which provides a direct view of the occupied band structure. While offering a fairly broad survey of progress in the field, we draw particular attention to STO, whose surface is so far the best-studied, and whose electronic structure is probably of the most immediate interest, given the ubiquitous use of STO substrates as the basis for conducting oxide interfaces. The ARPES studies provide crucial insights into the electronic band structure, orbital character, dimensionality/confinement, spin structure, and collective excitations in STO surfaces and related oxide surface/interface systems. The obtained knowledge increases our understanding of these complex materials and gives new perspectives on how to manipulate their properties.
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Affiliation(s)
- Nicholas C Plumb
- Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
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20
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Wang Z, Zhong Z, McKeown Walker S, Ristic Z, Ma JZ, Bruno FY, Riccò S, Sangiovanni G, Eres G, Plumb NC, Patthey L, Shi M, Mesot J, Baumberger F, Radovic M. Atomically Precise Lateral Modulation of a Two-Dimensional Electron Liquid in Anatase TiO 2 Thin Films. NANO LETTERS 2017; 17:2561-2567. [PMID: 28282495 DOI: 10.1021/acs.nanolett.7b00317] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Engineering the electronic band structure of two-dimensional electron liquids (2DELs) confined at the surface or interface of transition metal oxides is key to unlocking their full potential. Here we describe a new approach to tailoring the electronic structure of an oxide surface 2DEL demonstrating the lateral modulation of electronic states with atomic scale precision on an unprecedented length scale comparable to the Fermi wavelength. To this end, we use pulsed laser deposition to grow anatase TiO2 films terminated by a (1 × 4) in-plane surface reconstruction. Employing photostimulated chemical surface doping we induce 2DELs with tunable carrier densities that are confined within a few TiO2 layers below the surface. Subsequent in situ angle-resolved photoemission experiments demonstrate that the (1 × 4) surface reconstruction provides a periodic lateral perturbation of the electron liquid. This causes strong backfolding of the electronic bands, opening of unidirectional gaps and a saddle point singularity in the density of states near the chemical potential.
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Affiliation(s)
- Z Wang
- Swiss Light Source, Paul Scherrer Institut , CH-5232 Villigen PSI, Switzerland
- Department of Quantum Matter Physics, University of Geneva , 24 Quai Ernest-Ansermet, 1211 Geneva 4, Switzerland
| | - Z Zhong
- Institut für Theoretische Physik und Astrophysik, Universität Würzburg , Am Hubland, Würzburg 97070 Germany
| | - S McKeown Walker
- Department of Quantum Matter Physics, University of Geneva , 24 Quai Ernest-Ansermet, 1211 Geneva 4, Switzerland
| | - Z Ristic
- Institute of Condensed Matter Physics, École Polytechnique Fédérale de Lausanne (EPFL) , CH-1015 Lausanne, Switzerland
| | - J-Z Ma
- Beijing National Laboratory for Condensed Matter Physics, and Institute of Physics, Chinese Academy of Sciences , Beijing 100190, China
| | - F Y Bruno
- Department of Quantum Matter Physics, University of Geneva , 24 Quai Ernest-Ansermet, 1211 Geneva 4, Switzerland
| | - S Riccò
- Department of Quantum Matter Physics, University of Geneva , 24 Quai Ernest-Ansermet, 1211 Geneva 4, Switzerland
| | - G Sangiovanni
- Institut für Theoretische Physik und Astrophysik, Universität Würzburg , Am Hubland, Würzburg 97070 Germany
| | - G Eres
- Materials Science and Technology Division, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States
| | - N C Plumb
- Swiss Light Source, Paul Scherrer Institut , CH-5232 Villigen PSI, Switzerland
| | - L Patthey
- Swiss Light Source, Paul Scherrer Institut , CH-5232 Villigen PSI, Switzerland
- SwissFEL, Paul Scherrer Institut , CH-5232 Villigen PSI, Switzerland
| | - M Shi
- Swiss Light Source, Paul Scherrer Institut , CH-5232 Villigen PSI, Switzerland
| | - J Mesot
- Swiss Light Source, Paul Scherrer Institut , CH-5232 Villigen PSI, Switzerland
- Institute of Condensed Matter Physics, École Polytechnique Fédérale de Lausanne (EPFL) , CH-1015 Lausanne, Switzerland
- Laboratory for Solid State Physics, ETH Zürich , CH-8093 Zürich, Switzerland
| | - F Baumberger
- Swiss Light Source, Paul Scherrer Institut , CH-5232 Villigen PSI, Switzerland
- Department of Quantum Matter Physics, University of Geneva , 24 Quai Ernest-Ansermet, 1211 Geneva 4, Switzerland
| | - M Radovic
- Swiss Light Source, Paul Scherrer Institut , CH-5232 Villigen PSI, Switzerland
- SwissFEL, Paul Scherrer Institut , CH-5232 Villigen PSI, Switzerland
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21
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Coey JMD, Venkatesan M, Stamenov P. Surface magnetism of strontium titanate. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2016; 28:485001. [PMID: 27666311 DOI: 10.1088/0953-8984/28/48/485001] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
SrTiO3 plays a central role in oxide electronics. It is the substrate of choice for functional oxide heterostructures based on perovskite-structure thin-film stacks, and its surface or interface with a polar oxide such as LaAlO3 can become a 2D conductor because of electronic reconstruction or the presence of oxygen defects. Inconsistent reports of magnetic order in SrTiO3 abound in the literature. Here, we report a systematic experimental study aimed at establishing how and when SrTiO3 can develop a magnetic moment at room temperature. Polished (1 0 0), (1 1 0) or (1 1 1) crystal slices from four different suppliers are characterized before and after vacuum annealing at 750 °C, both in single-crystal and powdered form. Impurity content is analysed at the surface and in the bulk. Besides the underlying intrinsic diamagnetism of SrTiO3, magnetic signals are of three types-a Curie law susceptibility due to dilute magnetic impurities at the ppm level, a hysteretic temperature-dependent ferromagnetic impurity contribution, and a practically anhysteretic defect-related temperature-independent component that saturates in about 200 mT. The latter component is intrinsic. It is often the largest, reaching 10 μ B nm-2 of the surface area or more and dominating the magnetic response in low fields at room temperature. It is associated with defects near the surface, and can be destroyed by treatment with Tiron (C6H4Na2O8S2), an electron donor molecule that forms a strong complex with titanium at the surface. The origin of this unusual high-temperature ferromagnetic-like response is discussed.
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Affiliation(s)
- J M D Coey
- School of Physics, Trinity College, Dublin 2, Ireland
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22
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Dudy L, Sing M, Scheiderer P, Denlinger JD, Schütz P, Gabel J, Buchwald M, Schlueter C, Lee TL, Claessen R. In Situ Control of Separate Electronic Phases on SrTiO3 Surfaces by Oxygen Dosing. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2016; 28:7443-7449. [PMID: 27332795 DOI: 10.1002/adma.201600046] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/05/2016] [Revised: 05/10/2016] [Indexed: 06/06/2023]
Abstract
Insulating SrTiO3 (STO) can host 2D electron systems (2DESs) on its surfaces, caused by oxygen defects. This study shows that the STO surface exhibits phase separation once the 2DES is formed and relates this inhomogeneity to recently reported magnetic order at STO surfaces and interfaces. The results open pathways to exploit oxygen defects for engineering the electronic and magnetic properties of oxides.
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Affiliation(s)
- Lenart Dudy
- Physikalisches Institut and Röntgen Center for Complex Material Systems (RCCM), Universität Würzburg, D-97074, Würzburg, Germany.
| | - Michael Sing
- Physikalisches Institut and Röntgen Center for Complex Material Systems (RCCM), Universität Würzburg, D-97074, Würzburg, Germany
| | - Philipp Scheiderer
- Physikalisches Institut and Röntgen Center for Complex Material Systems (RCCM), Universität Würzburg, D-97074, Würzburg, Germany
| | - Jonathan D Denlinger
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA, 94270, USA
| | - Philipp Schütz
- Physikalisches Institut and Röntgen Center for Complex Material Systems (RCCM), Universität Würzburg, D-97074, Würzburg, Germany
| | - Judith Gabel
- Physikalisches Institut and Röntgen Center for Complex Material Systems (RCCM), Universität Würzburg, D-97074, Würzburg, Germany
| | - Mathias Buchwald
- Physikalisches Institut and Röntgen Center for Complex Material Systems (RCCM), Universität Würzburg, D-97074, Würzburg, Germany
| | | | - Tien-Lin Lee
- Diamond Light Source Ltd, Didcot, Oxfordshire, OX11 0DE, UK
| | - Ralph Claessen
- Physikalisches Institut and Röntgen Center for Complex Material Systems (RCCM), Universität Würzburg, D-97074, Würzburg, Germany
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23
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Wang Z, McKeown Walker S, Tamai A, Wang Y, Ristic Z, Bruno FY, de la Torre A, Riccò S, Plumb NC, Shi M, Hlawenka P, Sánchez-Barriga J, Varykhalov A, Kim TK, Hoesch M, King PDC, Meevasana W, Diebold U, Mesot J, Moritz B, Devereaux TP, Radovic M, Baumberger F. Tailoring the nature and strength of electron-phonon interactions in the SrTiO3(001) 2D electron liquid. NATURE MATERIALS 2016; 15:835-839. [PMID: 27064529 DOI: 10.1038/nmat4623] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/25/2015] [Accepted: 03/10/2016] [Indexed: 06/05/2023]
Abstract
Surfaces and interfaces offer new possibilities for tailoring the many-body interactions that dominate the electrical and thermal properties of transition metal oxides. Here, we use the prototypical two-dimensional electron liquid (2DEL) at the SrTiO3(001) surface to reveal a remarkably complex evolution of electron-phonon coupling with the tunable carrier density of this system. At low density, where superconductivity is found in the analogous 2DEL at the LaAlO3/SrTiO3 interface, our angle-resolved photoemission data show replica bands separated by 100 meV from the main bands. This is a hallmark of a coherent polaronic liquid and implies long-range coupling to a single longitudinal optical phonon branch. In the overdoped regime the preferential coupling to this branch decreases and the 2DEL undergoes a crossover to a more conventional metallic state with weaker short-range electron-phonon interaction. These results place constraints on the theoretical description of superconductivity and allow a unified understanding of the transport properties in SrTiO3-based 2DELs.
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Affiliation(s)
- Z Wang
- Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
- Department of Quantum Matter Physics, University of Geneva, 24 Quai Ernest-Ansermet, 1211 Geneva 4, Switzerland
| | - S McKeown Walker
- Department of Quantum Matter Physics, University of Geneva, 24 Quai Ernest-Ansermet, 1211 Geneva 4, Switzerland
| | - A Tamai
- Department of Quantum Matter Physics, University of Geneva, 24 Quai Ernest-Ansermet, 1211 Geneva 4, Switzerland
| | - Y Wang
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
- Department of Applied Physics, Stanford University, Stanford, California 94305, USA
| | - Z Ristic
- Institute of Condensed Matter Physics, École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - F Y Bruno
- Department of Quantum Matter Physics, University of Geneva, 24 Quai Ernest-Ansermet, 1211 Geneva 4, Switzerland
| | - A de la Torre
- Department of Quantum Matter Physics, University of Geneva, 24 Quai Ernest-Ansermet, 1211 Geneva 4, Switzerland
| | - S Riccò
- Department of Quantum Matter Physics, University of Geneva, 24 Quai Ernest-Ansermet, 1211 Geneva 4, Switzerland
| | - N C Plumb
- Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
| | - M Shi
- Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
| | - P Hlawenka
- Helmholtz-Zentrum Berlin für Materialien und Energie, Elektronenspeicherring BESSY-II, 12489 Berlin, Germany
| | - J Sánchez-Barriga
- Helmholtz-Zentrum Berlin für Materialien und Energie, Elektronenspeicherring BESSY-II, 12489 Berlin, Germany
| | - A Varykhalov
- Helmholtz-Zentrum Berlin für Materialien und Energie, Elektronenspeicherring BESSY-II, 12489 Berlin, Germany
| | - T K Kim
- Diamond Light Source, Harwell Campus, Didcot OX11 0DE, UK
| | - M Hoesch
- Diamond Light Source, Harwell Campus, Didcot OX11 0DE, UK
| | - P D C King
- SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews, Fife KY16 9SS, UK
| | - W Meevasana
- School of Physics and NANOTEC-SUT Center of Excellence on Advanced Functional Nanomaterials, Suranaree University of Technology, Nakhon Ratchasima 30000, Thailand
| | - U Diebold
- Institute of Applied Physics, Vienna University of Technology, Wiedner Hauptstrasse 8-10/134, A-1040 Vienna, Austria
| | - J Mesot
- Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
- Institute of Condensed Matter Physics, École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
- Laboratory for Solid State Physics, ETH Zürich, CH-8093 Zürich, Switzerland
| | - B Moritz
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
| | - T P Devereaux
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
- Geballe Laboratory for Advanced Materials, Stanford University, Stanford, California 94305, USA
| | - M Radovic
- Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
- SwissFEL, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
| | - F Baumberger
- Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
- Department of Quantum Matter Physics, University of Geneva, 24 Quai Ernest-Ansermet, 1211 Geneva 4, Switzerland
- SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews, Fife KY16 9SS, UK
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24
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Hong S, Nakhmanson SM, Fong DD. Screening mechanisms at polar oxide heterointerfaces. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2016; 79:076501. [PMID: 27308889 DOI: 10.1088/0034-4885/79/7/076501] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The interfaces of polar oxide heterostructures can display electronic properties unique from the oxides they border, as they require screening from either internal or external sources of charge. The screening mechanism depends on a variety of factors, including the band structure at the interface, the presence of point defects or adsorbates, whether or not the oxide is ferroelectric, and whether or not an external field is applied. In this review, we discuss both theoretical and experimental aspects of different screening mechanisms, giving special emphasis to ways in which the mechanism can be altered to provide novel or tunable functionalities. We begin with a theoretical introduction to the problem and highlight recent progress in understanding the impact of point defects on polar interfaces. Different case studies are then discussed, for both the high thickness regime, where interfaces must be screened and each interface can be considered separately, and the low thickness regime, where the degree and nature of screening can be manipulated and the interfaces are close enough to interact. We end with a brief outlook toward new developments in this rapidly progressing field.
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Affiliation(s)
- Seungbum Hong
- Materials Science Division, Argonne National Laboratory, Argonne, IL 60439, USA. Department of Materials Science & Engineering, KAIST, Daejeon 305-701, Korea
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25
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Taniuchi T, Motoyui Y, Morozumi K, Rödel TC, Fortuna F, Santander-Syro AF, Shin S. Imaging of room-temperature ferromagnetic nano-domains at the surface of a non-magnetic oxide. Nat Commun 2016; 7:11781. [PMID: 27283225 PMCID: PMC4906390 DOI: 10.1038/ncomms11781] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2015] [Accepted: 04/28/2016] [Indexed: 12/03/2022] Open
Abstract
Two-dimensional electron gases at oxide surfaces or interfaces show exotic ordered states of matter, like superconductivity, magnetism or spin-polarized states, and are a promising platform for alternative oxide-based electronics. Here we directly image a dense population of randomly distributed ferromagnetic domains of ∼40 nm typical sizes at room temperature at the oxygen-deficient surface of SrTiO3, a non-magnetic transparent insulator in the bulk. We use laser-based photoemission electron microscopy, an experimental technique that gives selective spin detection of the surface carriers, even in bulk insulators, with a high spatial resolution of 2.6 nm. We furthermore find that the Curie temperature in this system is as high as 900 K. These findings open perspectives for applications in nano-domain magnetism and spintronics using oxide-based devices, for instance through the nano-engineering of oxygen vacancies at surfaces or interfaces of transition-metal oxides. The surfaces of transition metal oxides exhibit a wide range of functional behaviours, from magnetism to superconductivity. Here, the authors use high-resolution microscopy to image the temperature dependent development of nanoscale ferromagnetic domains on an oxygen-deficient SrTiO3 surface.
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Affiliation(s)
- T Taniuchi
- Institute for Solid State Physics, University of Tokyo, Chiba 277-8581, Japan.,CREST, Japan Science and Technology Agency, Tokyo 102-0075, Japan
| | - Y Motoyui
- Institute for Solid State Physics, University of Tokyo, Chiba 277-8581, Japan
| | - K Morozumi
- Institute for Solid State Physics, University of Tokyo, Chiba 277-8581, Japan
| | - T C Rödel
- CSNSM, CNRS/IN2P3 and Université Paris-Sud, Bâtiments 104 et 108, Orsay 91405, France.,Synchrotron SOLEIL, L'Orme des Merisiers, Saint-Aubin-BP48, Gif-sur-Yvette 91192, France
| | - F Fortuna
- CSNSM, CNRS/IN2P3 and Université Paris-Sud, Bâtiments 104 et 108, Orsay 91405, France
| | - A F Santander-Syro
- CSNSM, CNRS/IN2P3 and Université Paris-Sud, Bâtiments 104 et 108, Orsay 91405, France
| | - S Shin
- Institute for Solid State Physics, University of Tokyo, Chiba 277-8581, Japan.,CREST, Japan Science and Technology Agency, Tokyo 102-0075, Japan
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26
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Rödel TC, Fortuna F, Sengupta S, Frantzeskakis E, Le Fèvre P, Bertran F, Mercey B, Matzen S, Agnus G, Maroutian T, Lecoeur P, Santander-Syro AF. Universal Fabrication of 2D Electron Systems in Functional Oxides. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2016; 28:1976-1980. [PMID: 26753522 DOI: 10.1002/adma.201505021] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/12/2015] [Revised: 11/19/2015] [Indexed: 06/05/2023]
Abstract
2D electron systems (2DESs) in functional oxides are promising for applications, but their fabrication and use, essentially limited to SrTiO3 -based heterostructures, are hampered by the need for growing complex oxide overlayers thicker than 2 nm using evolved techniques. It is demonstrated that thermal deposition of a monolayer of an elementary reducing agent suffices to create 2DESs in numerous oxides.
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Affiliation(s)
- Tobias Chris Rödel
- CSNSM, Univ. Paris-Sud, CNRS/IN2P3, Université Paris-Saclay, 91405, Orsay, France
- Synchrotron SOLEIL, L'Orme des Merisiers, Saint-Aubin-BP48, 91192, Gif-sur-Yvette, France
| | - Franck Fortuna
- CSNSM, Univ. Paris-Sud, CNRS/IN2P3, Université Paris-Saclay, 91405, Orsay, France
| | - Shamashis Sengupta
- Laboratoire de Physique des Solides, Univ. Paris-Sud, CNRS, Université Paris-Saclay, 91405, Orsay, France
| | | | - Patrick Le Fèvre
- Synchrotron SOLEIL, L'Orme des Merisiers, Saint-Aubin-BP48, 91192, Gif-sur-Yvette, France
| | - François Bertran
- Synchrotron SOLEIL, L'Orme des Merisiers, Saint-Aubin-BP48, 91192, Gif-sur-Yvette, France
| | - Bernard Mercey
- CRISMAT, ENSICAEN-CNRS UMR6508, 6 bd. Maréchal Juin, 14050, Caen, France
| | - Sylvia Matzen
- Institut d'Electronique Fondamentale, Univ. Paris-Sud, CNRS, Université Paris-Saclay, 91405, Orsay, France
| | - Guillaume Agnus
- Institut d'Electronique Fondamentale, Univ. Paris-Sud, CNRS, Université Paris-Saclay, 91405, Orsay, France
| | - Thomas Maroutian
- Institut d'Electronique Fondamentale, Univ. Paris-Sud, CNRS, Université Paris-Saclay, 91405, Orsay, France
| | - Philippe Lecoeur
- Institut d'Electronique Fondamentale, Univ. Paris-Sud, CNRS, Université Paris-Saclay, 91405, Orsay, France
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27
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Chen C, Avila J, Frantzeskakis E, Levy A, Asensio MC. Observation of a two-dimensional liquid of Fröhlich polarons at the bare SrTiO3 surface. Nat Commun 2015; 6:8585. [PMID: 26489376 PMCID: PMC4639792 DOI: 10.1038/ncomms9585] [Citation(s) in RCA: 106] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2015] [Accepted: 09/08/2015] [Indexed: 11/24/2022] Open
Abstract
The polaron is a quasi-particle formed by a conduction electron (or hole) together with its self-induced polarization in a polar semiconductor or an ionic crystal. Among various polarizable examples of complex oxides, strontium titanate (SrTiO3) is one of the most studied. Here we examine the carrier type and the interplay of inner degrees of freedom (for example, charge, lattice, orbital) in SrTiO3. We report the experimental observation of Fröhlich polarons, or large polarons, at the bare SrTiO3 surface prepared by vacuum annealing. Systematic analyses of angle-resolved photoemission spectroscopy and X-ray absorption spectra show that these Fröhlich polarons are two-dimensional and only exist with inversion symmetry breaking by two-dimensional oxygen vacancies. Our discovery provides a rare solvable field theoretical model, and suggests the relevance of large (bi)polarons for superconductivity in perovskite oxides, as well as in high-temperature superconductors. A polaron is a quasiparticle formed through the strong interaction between an electron and the ions in a crystalline solid. Here, the authors observe Fröhlich polarons, formed by the coupling of electrons and long-wavelength optical phonons, in strontium titanate.
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Affiliation(s)
- Chaoyu Chen
- Synchrotron SOLEIL, Beamline ANTARES, L'Orme des Merisiers, Saint Aubin-BP 48, Gif surYvette 91192, France
| | - José Avila
- Synchrotron SOLEIL, Beamline ANTARES, L'Orme des Merisiers, Saint Aubin-BP 48, Gif surYvette 91192, France
| | - Emmanouil Frantzeskakis
- Synchrotron SOLEIL, Beamline ANTARES, L'Orme des Merisiers, Saint Aubin-BP 48, Gif surYvette 91192, France
| | - Anna Levy
- Synchrotron SOLEIL, Beamline ANTARES, L'Orme des Merisiers, Saint Aubin-BP 48, Gif surYvette 91192, France
| | - Maria C Asensio
- Synchrotron SOLEIL, Beamline ANTARES, L'Orme des Merisiers, Saint Aubin-BP 48, Gif surYvette 91192, France
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28
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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}. PHYSICAL REVIEW LETTERS 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] [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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29
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Diez M, Monteiro AMRVL, Mattoni G, Cobanera E, Hyart T, Mulazimoglu E, Bovenzi N, Beenakker CWJ, Caviglia AD. Giant Negative Magnetoresistance Driven by Spin-Orbit Coupling at the LaAlO3/SrTiO3 Interface. PHYSICAL REVIEW LETTERS 2015; 115:016803. [PMID: 26182114 DOI: 10.1103/physrevlett.115.016803] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/16/2015] [Indexed: 06/04/2023]
Abstract
The LaAlO3/SrTiO3 interface hosts a two-dimensional electron system that is unusually sensitive to the application of an in-plane magnetic field. Low-temperature experiments have revealed a giant negative magnetoresistance (dropping by 70%), attributed to a magnetic-field induced transition between interacting phases of conduction electrons with Kondo-screened magnetic impurities. Here we report on experiments over a broad temperature range, showing the persistence of the magnetoresistance up to the 20 K range--indicative of a single-particle mechanism. Motivated by a striking correspondence between the temperature and carrier density dependence of our magnetoresistance measurements we propose an alternative explanation. Working in the framework of semiclassical Boltzmann transport theory we demonstrate that the combination of spin-orbit coupling and scattering from finite-range impurities can explain the observed magnitude of the negative magnetoresistance, as well as the temperature and electron density dependence.
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Affiliation(s)
- M Diez
- Instituut-Lorentz, Universiteit Leiden, P.O. Box 9506, 2300 RA Leiden, Netherlands
| | - A M R V L Monteiro
- Kavli Institute of Nanoscience, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, Netherlands
| | - G Mattoni
- Kavli Institute of Nanoscience, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, Netherlands
| | - E Cobanera
- Instituut-Lorentz, Universiteit Leiden, P.O. Box 9506, 2300 RA Leiden, Netherlands
- Institute for Theoretical Physics, Center for Extreme Matter and Emergent Phenomena, Utrecht University, Leuvenlaan 4, 3584 CE Utrecht, Netherlands
| | - T Hyart
- Instituut-Lorentz, Universiteit Leiden, P.O. Box 9506, 2300 RA Leiden, Netherlands
- Department of Physics and Nanoscience Center, University of Jyväskylä, P.O. Box 35 (YFL), FI-40014 University of Jyväskylä, Finland
| | - E Mulazimoglu
- Kavli Institute of Nanoscience, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, Netherlands
| | - N Bovenzi
- Instituut-Lorentz, Universiteit Leiden, P.O. Box 9506, 2300 RA Leiden, Netherlands
| | - C W J Beenakker
- Instituut-Lorentz, Universiteit Leiden, P.O. Box 9506, 2300 RA Leiden, Netherlands
| | - A D Caviglia
- Kavli Institute of Nanoscience, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, Netherlands
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30
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Gor'kov LP. Antiferromagnetism of two-dimensional electronic gas on light-irradiated SrTiO3 and at LaAlO3/SrTiO3 interfaces. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2015; 27:252001. [PMID: 26020368 DOI: 10.1088/0953-8984/27/25/252001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
To gain an insight into the origin of tunable two-dimensional (2D) electronic liquid at the interfaces of transition-metal oxides, we address properties of a conducting layer on the light-irradiated surfaces of SrTiO3; the energy spectrum of the latter is known and consists of the titanium dxz/dyz and dxy bands. Recently, Santander-Syro et al (2014 Nature Mater. 13 1085) revealed that the dxy bands actually comprise two chiral branches with the Kramers degeneracy at the zone center lifted in the absence of a magnetic moment. We suggest that interacting electrons on the irradiated SrTiO3 go over into a magnetic phase as the result of one of the instabilities of the 2D Fermi liquid with exchange interactions, and point out the concrete antiferromagnetic order parameter. Large energy scales of the order of Fermi energy ∼0.1 eV inherent in this mechanism warrant stability of the magnetic ground state against ever-present effects of disorder. Arguments are given that electrons at the irradiated SrTiO3 surface and at the LaAlO3/SrTiO3 interfaces undergo a kind of first-order transformation into one and the same phase of the 2D electronic Fermi liquid with reduced magnetic symmetry.
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Affiliation(s)
- L P Gor'kov
- NHMFL, Florida State University, 1800 East Paul Dirac Drive, Tallahassee, FL 32310, USA. L.D. Landau Institute for Theoretical Physics of the RAS, Chernogolovka 142432, Russia
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31
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Chen Y, Trier F, Kasama T, Christensen DV, Bovet N, Balogh ZI, Li H, Thydén KTS, Zhang W, Yazdi S, Norby P, Pryds N, Linderoth S. Creation of high mobility two-dimensional electron gases via strain induced polarization at an otherwise nonpolar complex oxide interface. NANO LETTERS 2015; 15:1849-1854. [PMID: 25692804 DOI: 10.1021/nl504622w] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The discovery of two-dimensional electron gases (2DEGs) in SrTiO3-based heterostructures provides new opportunities for nanoelectronics. Herein, we create a new type of oxide 2DEG by the epitaxial-strain-induced polarization at an otherwise nonpolar perovskite-type interface of CaZrO3/SrTiO3. Remarkably, this heterointerface is atomically sharp and exhibits a high electron mobility exceeding 60,000 cm(2) V(-1) s(-1) at low temperatures. The 2DEG carrier density exhibits a critical dependence on the film thickness, in good agreement with the polarization induced 2DEG scheme.
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Affiliation(s)
- Yunzhong Chen
- Department of Energy Conversion and Storage, Technical University of Denmark , Risø Campus, 4000 Roskilde, Denmark
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32
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Santander-Syro AF, Fortuna F, Bareille C, Rödel TC, Landolt G, Plumb NC, Dil JH, Radović M. Giant spin splitting of the two-dimensional electron gas at the surface of SrTiO3. NATURE MATERIALS 2014; 13:1085-1090. [PMID: 25306421 DOI: 10.1038/nmat4107] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/29/2014] [Accepted: 09/05/2014] [Indexed: 06/04/2023]
Abstract
Two-dimensional electron gases (2DEGs) forming at the interfaces of transition metal oxides exhibit a range of properties, including tunable insulator-superconductor-metal transitions, large magnetoresistance, coexisting ferromagnetism and superconductivity, and a spin splitting of a few meV (refs 10, 11). Strontium titanate (SrTiO3), the cornerstone of such oxide-based electronics, is a transparent, non-magnetic, wide-bandgap insulator in the bulk, and has recently been found to host a surface 2DEG (refs 12-15). The most strongly confined carriers within this 2DEG comprise two subbands, separated by an energy gap of 90 meV and forming concentric circular Fermi surfaces. Using spin- and angle-resolved photoemission spectroscopy (SARPES), we show that the electron spins in these subbands have opposite chiralities. Although the Rashba effect might be expected to give rise to such spin textures, the giant splitting of almost 100 meV at the Fermi level is far larger than anticipated. Moreover, in contrast to a simple Rashba system, the spin-polarized subbands are non-degenerate at the Brillouin zone centre. This degeneracy can be lifted by time-reversal symmetry breaking, implying the possible existence of magnetic order. These results show that confined electronic states at oxide surfaces can be endowed with novel, non-trivial properties that are both theoretically challenging to anticipate and promising for technological applications.
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Affiliation(s)
- A F Santander-Syro
- CSNSM, Université Paris-Sud and CNRS/IN2P3, Bâtiments 104 et 108, 91405 Orsay cedex, France
| | - F Fortuna
- CSNSM, Université Paris-Sud and CNRS/IN2P3, Bâtiments 104 et 108, 91405 Orsay cedex, France
| | - C Bareille
- CSNSM, Université Paris-Sud and CNRS/IN2P3, Bâtiments 104 et 108, 91405 Orsay cedex, France
| | - T C Rödel
- 1] CSNSM, Université Paris-Sud and CNRS/IN2P3, Bâtiments 104 et 108, 91405 Orsay cedex, France [2] Synchrotron SOLEIL, L'Orme des Merisiers, Saint-Aubin-BP48, 91192 Gif-sur-Yvette, France
| | - G Landolt
- 1] Physik-Institut, Universität Zürich, Winterthurerstrasse 190 8057 Zürich, Switzerland [2] Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
| | - N C Plumb
- Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
| | - J H Dil
- 1] Physik-Institut, Universität Zürich, Winterthurerstrasse 190 8057 Zürich, Switzerland [2] Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland [3] Institute of Condensed Matter Physics, Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland
| | - M Radović
- 1] Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland [2] Institute of Condensed Matter Physics, Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland [3] SwissFEL, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
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33
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Walker SM, de la Torre A, Bruno FY, Tamai A, Kim TK, Hoesch M, Shi M, Bahramy MS, King PDC, Baumberger F. Control of a two-dimensional electron gas on SrTiO₃(111) by atomic oxygen. PHYSICAL REVIEW LETTERS 2014; 113:177601. [PMID: 25379937 DOI: 10.1103/physrevlett.113.177601] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/12/2014] [Indexed: 06/04/2023]
Abstract
We report on the formation of a two-dimensional electron gas (2DEG) at the bare surface of (111) oriented SrTiO3. Angle resolved photoemission experiments reveal highly itinerant carriers with a sixfold symmetric Fermi surface and strongly anisotropic effective masses. The electronic structure of the 2DEG is in good agreement with self-consistent tight-binding supercell calculations that incorporate a confinement potential due to surface band bending. We further demonstrate that alternate exposure of the surface to ultraviolet light and atomic oxygen allows tuning of the carrier density and the complete suppression of the 2DEG.
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Affiliation(s)
- S McKeown Walker
- Département de Physique de la Matière Condensée, Universitée de Genève, 24 Quai Ernest-Ansermet, 1211 Genève 4, Switzerland
| | - A de la Torre
- Département de Physique de la Matière Condensée, Universitée de Genève, 24 Quai Ernest-Ansermet, 1211 Genève 4, Switzerland
| | - F Y Bruno
- Département de Physique de la Matière Condensée, Universitée de Genève, 24 Quai Ernest-Ansermet, 1211 Genève 4, Switzerland
| | - A Tamai
- Département de Physique de la Matière Condensée, Universitée de Genève, 24 Quai Ernest-Ansermet, 1211 Genève 4, Switzerland
| | - T K Kim
- Diamond Light Source, Harwell Campus, Didcot OX11 0DE, United Kingdom
| | - M Hoesch
- Diamond Light Source, Harwell Campus, Didcot OX11 0DE, United Kingdom
| | - M Shi
- Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
| | - M S Bahramy
- Quantum-Phase Electronics Center, Department of Applied Physics, The University of Tokyo, Tokyo 113-8656, Japan and RIKEN Center for Emergent Matter Science (CEMS), Wako 351-0198, Japan
| | - P D C King
- SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews, Fife KY16 9SS, United Kingdom
| | - F Baumberger
- Département de Physique de la Matière Condensée, Universitée de Genève, 24 Quai Ernest-Ansermet, 1211 Genève 4, Switzerland and Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland and SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews, Fife KY16 9SS, United Kingdom
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