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Brinkman SS, Tan XL, Brekke B, Mathisen AC, Finnseth Ø, Schenk RJ, Hagiwara K, Huang MJ, Buck J, Kalläne M, Hoesch M, Rossnagel K, Ou Yang KH, Lin MT, Shu GJ, Chen YJ, Tusche C, Bentmann H. Chirality-Driven Orbital Angular Momentum and Circular Dichroism in CoSi. PHYSICAL REVIEW LETTERS 2024; 132:196402. [PMID: 38804933 DOI: 10.1103/physrevlett.132.196402] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/05/2024] [Accepted: 03/20/2024] [Indexed: 05/29/2024]
Abstract
Chiral crystals and molecules were recently predicted to form an intriguing platform for unconventional orbital physics. Here, we report the observation of chirality-driven orbital textures in the bulk electronic structure of CoSi, a prototype member of the cubic B20 family of chiral crystals. Using circular dichroism in soft x-ray angle-resolved photoemission, we demonstrate the formation of a bulk orbital-angular-momentum texture and monopolelike orbital-momentum locking that depends on crystal handedness. We introduce the intrinsic chiral circular dichroism, icCD, as a differential photoemission observable and a natural probe of chiral electron states. Our findings render chiral crystals promising for spin-orbitronics applications.
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Affiliation(s)
- Stefanie Suzanne Brinkman
- Center for Quantum Spintronics, Department of Physics, Norwegian University of Science and Technology, 7491 Trondheim, Norway
| | - Xin Liang Tan
- Center for Quantum Spintronics, Department of Physics, Norwegian University of Science and Technology, 7491 Trondheim, Norway
- Peter Grünberg Institut (PGI-6), Forschungszentrum Jülich, Jülich 52425, Germany
- Faculty of Physics, University of Duisburg-Essen, Duisburg 47057, Germany
| | - Bjørnulf Brekke
- Center for Quantum Spintronics, Department of Physics, Norwegian University of Science and Technology, 7491 Trondheim, Norway
| | - Anders Christian Mathisen
- Center for Quantum Spintronics, Department of Physics, Norwegian University of Science and Technology, 7491 Trondheim, Norway
| | - Øyvind Finnseth
- Department of Materials Science and Engineering, Norwegian University of Science and Technology, 7491 Trondheim, Norway
| | - Richard Justin Schenk
- Center for Quantum Spintronics, Department of Physics, Norwegian University of Science and Technology, 7491 Trondheim, Norway
| | - Kenta Hagiwara
- Peter Grünberg Institut (PGI-6), Forschungszentrum Jülich, Jülich 52425, Germany
- Faculty of Physics, University of Duisburg-Essen, Duisburg 47057, Germany
| | - Meng-Jie Huang
- Ruprecht Haensel Laboratory, Kiel University, 24098 Kiel, Germany
- Ruprecht Haensel Laboratory, DESY, 22607 Hamburg, Germany
- Deutsches Elektronen-Synchrotron DESY, Notkestraße 85, 22607 Hamburg, Germany
| | - Jens Buck
- Ruprecht Haensel Laboratory, Kiel University, 24098 Kiel, Germany
- Ruprecht Haensel Laboratory, DESY, 22607 Hamburg, Germany
- Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität zu Kiel, 24098 Kiel, Germany
| | - Matthias Kalläne
- Ruprecht Haensel Laboratory, Kiel University, 24098 Kiel, Germany
- Ruprecht Haensel Laboratory, DESY, 22607 Hamburg, Germany
- Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität zu Kiel, 24098 Kiel, Germany
| | - Moritz Hoesch
- Deutsches Elektronen-Synchrotron DESY, Notkestraße 85, 22607 Hamburg, Germany
| | - Kai Rossnagel
- Ruprecht Haensel Laboratory, Kiel University, 24098 Kiel, Germany
- Ruprecht Haensel Laboratory, DESY, 22607 Hamburg, Germany
- Deutsches Elektronen-Synchrotron DESY, Notkestraße 85, 22607 Hamburg, Germany
- Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität zu Kiel, 24098 Kiel, Germany
| | - Kui-Hon Ou Yang
- Department of Physics, National Taiwan University, Taipei 10617, Taiwan
| | - Minn-Tsong Lin
- Department of Physics, National Taiwan University, Taipei 10617, Taiwan
- Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan
- Research Center for Applied Sciences, Academia Sinica, Taipei 11529, Taiwan
| | - Guo-Jiun Shu
- Department of Materials and Mineral Resources Engineering, National Taipei University of Technology, Taipei 10608, Taiwan
| | - Ying-Jiun Chen
- Peter Grünberg Institut (PGI-6), Forschungszentrum Jülich, Jülich 52425, Germany
- Faculty of Physics, University of Duisburg-Essen, Duisburg 47057, Germany
- Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons and Peter Grünberg Institute, Forschungszentrum Jülich, 52425 Jülich, Germany
| | - Christian Tusche
- Peter Grünberg Institut (PGI-6), Forschungszentrum Jülich, Jülich 52425, Germany
- Faculty of Physics, University of Duisburg-Essen, Duisburg 47057, Germany
| | - Hendrik Bentmann
- Center for Quantum Spintronics, Department of Physics, Norwegian University of Science and Technology, 7491 Trondheim, Norway
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2
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Huang S, Ghosh N, Niu C, Chen YP, Ye PD, Xu X. Optically Gated Electrostatic Field-Effect Thermal Transistor. NANO LETTERS 2024; 24:5139-5145. [PMID: 38639471 DOI: 10.1021/acs.nanolett.3c05085] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/20/2024]
Abstract
Dynamic tuning of thermal transport in solids is scientifically intriguing with wide applications for thermal transport control in electronic devices. In this work, we demonstrate a thermal transistor, a device in which heat flow can be regulated using external control, realized in a topological insulator (TI) through the topological surface states. The tuning of thermal transport is achieved by using optical gating of a thin dielectric layer deposited on the TI film. The gate-dependent thermal conductivity is measured using micro-Raman thermometry. The transistor has a large ON/OFF ratio of 2.8 at room temperature and can be continuously and repetitively switched in tens of seconds by optical gating and potentially much faster by electrical gating. Such thermal transistors with a large ON/OFF ratio and fast switching times offer the possibilities of smart thermal devices for active thermal management and control in future electronic systems.
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Affiliation(s)
- Shouyuan Huang
- School of Mechanical Engineering, Purdue University, West Lafayette, Indiana 47907, United States
- Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, United States
| | - Neil Ghosh
- School of Mechanical Engineering, Purdue University, West Lafayette, Indiana 47907, United States
- Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, United States
| | - Chang Niu
- Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, United States
- Elmore Family School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47907, United States
| | - Yong P Chen
- Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, United States
- Elmore Family School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47907, United States
- Department of Physics and Astronomy, Purdue University, West Lafayette, Indiana 47907, United States
- Purdue Quantum Science and Engineering Institute, Purdue University, West Lafayette, Indiana 47907, United States
| | - Peide D Ye
- Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, United States
- Elmore Family School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47907, United States
- Purdue Quantum Science and Engineering Institute, Purdue University, West Lafayette, Indiana 47907, United States
| | - Xianfan Xu
- School of Mechanical Engineering, Purdue University, West Lafayette, Indiana 47907, United States
- Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, United States
- Elmore Family School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47907, United States
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Choi GS, Park S, An ES, Bae J, Shin I, Kang BT, Won CJ, Cheong SW, Lee HW, Lee GH, Cho WJ, Kim JS. Highly Efficient Room-Temperature Spin-Orbit-Torque Switching in a Van der Waals Heterostructure of Topological Insulator and Ferromagnet. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2024:e2400893. [PMID: 38520060 DOI: 10.1002/advs.202400893] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/01/2024] [Indexed: 03/25/2024]
Abstract
All-Van der Waals (vdW)-material-based heterostructures with atomically sharp interfaces offer a versatile platform for high-performing spintronic functionalities at room temperature. One of the key components is vdW topological insulators (TIs), which can produce a strong spin-orbit-torque (SOT) through the spin-momentum locking of their topological surface state (TSS). However, the relatively low conductance of the TSS introduces a current leakage problem through the bulk states of the TI or the adjacent ferromagnetic metal layers, reducing the interfacial charge-to-spin conversion efficiency (qICS). Here, a vdW heterostructure is used consisting of atomically-thin layers of a bulk-insulating TI Sn-doped Bi1.1Sb0.9Te2S1 and a room-temperature ferromagnet Fe3GaTe2, to enhance the relative current ratio on the TSS up to ≈20%. The resulting qICS reaches ≈1.65 nm-1 and the critical current density Jc ≈0.9 × 106 Acm-2 at 300 K, surpassing the performance of TI-based and heavy-metal-based SOT devices. These findings demonstrate that an all-vdW heterostructure with thickness optimization offers a promising platform for efficient current-controlled magnetization switching at room temperature.
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Affiliation(s)
- Gyu Seung Choi
- Department of Physics, Pohang University of Science and Technology, Pohang, 37673, Republic of Korea
- Center for Artificial Low Dimensional Electronic Systems, Institute for Basic Science (IBS), Pohang, 37673, Republic of Korea
| | - Sungyu Park
- Department of Physics, Pohang University of Science and Technology, Pohang, 37673, Republic of Korea
| | - Eun-Su An
- Department of Physics, Pohang University of Science and Technology, Pohang, 37673, Republic of Korea
- Center for Artificial Low Dimensional Electronic Systems, Institute for Basic Science (IBS), Pohang, 37673, Republic of Korea
| | - Juhong Bae
- Department of Physics, Pohang University of Science and Technology, Pohang, 37673, Republic of Korea
| | - Inseob Shin
- Department of Physics, Pohang University of Science and Technology, Pohang, 37673, Republic of Korea
| | - Beom Tak Kang
- Department of Physics, Pohang University of Science and Technology, Pohang, 37673, Republic of Korea
- Center for Artificial Low Dimensional Electronic Systems, Institute for Basic Science (IBS), Pohang, 37673, Republic of Korea
| | - Choong Jae Won
- Center for Complex Phase of Materials, Max Planck POSTECH/Korea Research Initiative, Pohang, 37673, Republic of Korea
- Laboratory for Pohang Emergent Materials, Department of Physics, POSTECH, Pohang, 37673, Republic of Korea
| | - Sang-Wook Cheong
- Center for Complex Phase of Materials, Max Planck POSTECH/Korea Research Initiative, Pohang, 37673, Republic of Korea
- Laboratory for Pohang Emergent Materials, Department of Physics, POSTECH, Pohang, 37673, Republic of Korea
- Rutgers Center for Emergent Materials and Department of Physics and Astronomy, Rutgers University, Piscataway, NJ, 08854, USA
| | - Hyun-Woo Lee
- Department of Physics, Pohang University of Science and Technology, Pohang, 37673, Republic of Korea
| | - Gil-Ho Lee
- Department of Physics, Pohang University of Science and Technology, Pohang, 37673, Republic of Korea
| | - Won Joon Cho
- Device Research Center, Samsung Advanced Institute of Technology (SAIT), Samsung Electronics Co., Ltd, 130 Samsung-ro, Yeongtong-gu, Suwon-si, Gyeonggi-do, 16678, Republic of Korea
| | - Jun Sung Kim
- Department of Physics, Pohang University of Science and Technology, Pohang, 37673, Republic of Korea
- Center for Artificial Low Dimensional Electronic Systems, Institute for Basic Science (IBS), Pohang, 37673, Republic of Korea
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4
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Wang X, Tian H, Li X, Wang F, Zhai L, Zhu X, Liu JM, Yang Y. Pressure-Induced Topological Phase Transition and Large Rashba Effect in Halide Double Perovskite. J Phys Chem Lett 2024; 15:1477-1483. [PMID: 38295292 DOI: 10.1021/acs.jpclett.3c03432] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2024]
Abstract
In general, hydrostatic pressure can suppress ferroelectric polarization and further reduce Rashba spin-splitting, considering the spin-orbit coupling effect. Here, we present the design of ferroelectric double perovskite Cs2SnSiI6, which exhibits the anomalous enhancement of Rashba spin-splitting parameters by pressure-induced ferroelectric topological order. The Rashba effect is nonlinear with the decrease in polarization under pressure and reaches a maximum at the pressure-induced Weyl semimetal (WSM) state between the transition from a normal insulator (NI) to a topological insulator (TI). Furthermore, we discover that controlling ferroelectric polarization with an electric field can also induce the topological transition with a large Rashba spin-splitting but under a lower critical pressure. These discoveries show a tunable gaint Rashba effect and pressure-induced topological phase transition for Cs2SnSiI6, which can promote future research on the interaction between the Rashba effect and topological order, and its application to new electronic and spintronic devices.
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Affiliation(s)
- Xinyu Wang
- The School of Mathematics and Physics, Jiangsu University of Technology, Changzhou 213001, China
| | - Hao Tian
- School of Physics and Electronic Engineering, Zhengzhou Normal University, Zhengzhou 450044, China
| | - Xu Li
- Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210093, China
- Jiangsu Key Laboratory of Artificial Functional Materials, Department of Materials Science and Engineering, Nanjing University, Nanjing 210093, China
| | - Fengfei Wang
- The School of Mathematics and Physics, Jiangsu University of Technology, Changzhou 213001, China
| | - Liangjun Zhai
- The School of Mathematics and Physics, Jiangsu University of Technology, Changzhou 213001, China
| | - Xiaoqin Zhu
- The School of Mathematics and Physics, Jiangsu University of Technology, Changzhou 213001, China
| | - Jun-Ming Liu
- Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210093, China
| | - Yurong Yang
- Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210093, China
- Jiangsu Key Laboratory of Artificial Functional Materials, Department of Materials Science and Engineering, Nanjing University, Nanjing 210093, China
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Krizman G, Zakusylo T, Sajeev L, Hajlaoui M, Takashiro T, Rosmus M, Olszowska N, Kołodziej JJ, Bauer G, Caha O, Springholz G. A Novel Ferroelectric Rashba Semiconductor. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2023:e2310278. [PMID: 38100676 DOI: 10.1002/adma.202310278] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/04/2023] [Revised: 12/08/2023] [Indexed: 12/17/2023]
Abstract
Fast, reversible, and low-power manipulation of the spin texture is crucial for next generation spintronic devices like non-volatile bipolar memories, switchable spin current injectors or spin field effect transistors. Ferroelectric Rashba semiconductors (FERSC) are the ideal class of materials for the realization of such devices. Their ferroelectric character enables an electronic control of the Rashba-type spin texture by means of the reversible and switchable polarization. Yet, only very few materials are established to belong to this class of multifunctional materials. Here, Pb1- x Gex Te is unraveled as a novel FERSC system down to nanoscale. The ferroelectric phase transition and concomitant lattice distortion are demonstrated by temperature dependent X-ray diffraction, and their effect on electronic properties are measured by angle-resolved photoemission spectroscopy. In few nanometer-thick epitaxial heterostructures, a large Rashba spin-splitting is exhibiting a wide tuning range as a function of temperature and Ge content. This work defines Pb1- x Gex Te as a high-potential FERSC system for spintronic applications.
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Affiliation(s)
- Gauthier Krizman
- Institut für Halbleiter und Festkörperphysik, Johannes Kepler Universität, Altenberger Strasse 69, Linz, 4040, Austria
| | - Tetiana Zakusylo
- Institut für Halbleiter und Festkörperphysik, Johannes Kepler Universität, Altenberger Strasse 69, Linz, 4040, Austria
| | - Lakshmi Sajeev
- Department of Condensed Matter Physics, Masaryk University, Kotlárská 2, Brno, 61137, Czech Republic
| | - Mahdi Hajlaoui
- Institut für Halbleiter und Festkörperphysik, Johannes Kepler Universität, Altenberger Strasse 69, Linz, 4040, Austria
| | - Takuya Takashiro
- Institut für Halbleiter und Festkörperphysik, Johannes Kepler Universität, Altenberger Strasse 69, Linz, 4040, Austria
| | - Marcin Rosmus
- National Synchrotron Radiation Centre SOLARIS, Jagiellonian University, Czerwone Maki 98, Krakow, 30-392, Poland
| | - Natalia Olszowska
- National Synchrotron Radiation Centre SOLARIS, Jagiellonian University, Czerwone Maki 98, Krakow, 30-392, Poland
| | - Jacek J Kołodziej
- National Synchrotron Radiation Centre SOLARIS, Jagiellonian University, Czerwone Maki 98, Krakow, 30-392, Poland
- Faculty of Physics, Astronomy and Applied Computer Science, Jagiellonian University, Ul. Prof. Stanislawa Lojasiewizca 11, Krakow, 30-348, Poland
| | - Günther Bauer
- Institut für Halbleiter und Festkörperphysik, Johannes Kepler Universität, Altenberger Strasse 69, Linz, 4040, Austria
| | - Ondrej Caha
- Department of Condensed Matter Physics, Masaryk University, Kotlárská 2, Brno, 61137, Czech Republic
| | - Gunther Springholz
- Institut für Halbleiter und Festkörperphysik, Johannes Kepler Universität, Altenberger Strasse 69, Linz, 4040, Austria
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Chen Z, Sui X, Li Z, Li Y, Liu X, Zhang Y. Quantum-sized topological insulators/semimetals enable ultrahigh and broadband saturable absorption. NANOSCALE HORIZONS 2023; 8:1686-1694. [PMID: 37702034 DOI: 10.1039/d3nh00282a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/14/2023]
Abstract
Two-dimensional topological insulators/semimetals have recently attracted much attention. However, quantum-sized topological insulators/semimetals with intrinsic characteristics have never been reported before. Herein, we report the high-yield production of topological insulator (i.e., Bi2Se3 and Sb2Te3) and semimetal (i.e., TiS2) quantum sheets (QSs) with monolayer structures and sub-4 nm lateral sizes. Both linear and nonlinear optical performances of the QSs are investigated. The QS dispersions present remarkable photoluminescence with excitation wavelength-, concentration-, and solvent-dependence. The solution-processed QSs-poly(methyl methacrylate) (PMMA) hybrid thin films demonstrate exceptional nonlinear saturation absorption (NSA). Particularly, Bi2Se3 QSs-PMMA enables record-high NSA performance with a broadband feature. Specifically, the (absolute) modulation depths up to 71.6 and 72.4% and saturation intensities down to 1.52 and 0.49 MW cm-2 are achieved at 532 and 800 nm, respectively. Such a phenomenal NSA performance would greatly facilitate their applications in mode-locked lasers and related fields.
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Affiliation(s)
- Zhexue Chen
- CAS Key Laboratory of Nanosystem and Hierarchical Fabrication, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing 100190, P. R. China.
- University of Chinese Academy of Sciences, Beijing 100049, P. R. China
| | - Xinyu Sui
- University of Chinese Academy of Sciences, Beijing 100049, P. R. China
- CAS Key Laboratory of Standardization and Measurement for Nanotechnology, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing 100190, P. R. China
| | - Zhangqiang Li
- CAS Key Laboratory of Nanosystem and Hierarchical Fabrication, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing 100190, P. R. China.
- University of Chinese Academy of Sciences, Beijing 100049, P. R. China
| | - Yueqi Li
- CAS Key Laboratory of Nanosystem and Hierarchical Fabrication, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing 100190, P. R. China.
- University of Chinese Academy of Sciences, Beijing 100049, P. R. China
| | - Xinfeng Liu
- University of Chinese Academy of Sciences, Beijing 100049, P. R. China
- CAS Key Laboratory of Standardization and Measurement for Nanotechnology, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing 100190, P. R. China
| | - Yong Zhang
- CAS Key Laboratory of Nanosystem and Hierarchical Fabrication, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing 100190, P. R. China.
- University of Chinese Academy of Sciences, Beijing 100049, P. R. China
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Kremer G, Mahmoudi A, M'Foukh A, Bouaziz M, Rahimi M, Della Rocca ML, Le Fèvre P, Dayen JF, Bertran F, Matzen S, Pala M, Chaste J, Oehler F, Ouerghi A. Quantum Confinement and Electronic Structure at the Surface of van der Waals Ferroelectric α-In 2Se 3. ACS NANO 2023; 17:18924-18931. [PMID: 37585336 DOI: 10.1021/acsnano.3c04186] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/18/2023]
Abstract
Two-dimensional (2D) ferroelectric (FE) materials are promising compounds for next-generation nonvolatile memories due to their low energy consumption and high endurance. Among them, α-In2Se3 has drawn particular attention due to its in- and out-of-plane ferroelectricity, whose robustness has been demonstrated down to the monolayer limit. This is a relatively uncommon behavior since most bulk FE materials lose their ferroelectric character at the 2D limit due to the depolarization field. Using angle resolved photoemission spectroscopy (ARPES), we unveil another unusual 2D phenomenon appearing in 2H α-In2Se3 single crystals, the occurrence of a highly metallic two-dimensional electron gas (2DEG) at the surface of vacuum-cleaved crystals. This 2DEG exhibits two confined states, which correspond to an electron density of approximately 1013 electrons/cm2, also confirmed by thermoelectric measurements. Combination of ARPES and density functional theory (DFT) calculations reveals a direct band gap of energy equal to 1.3 ± 0.1 eV, with the bottom of the conduction band localized at the center of the Brillouin zone, just below the Fermi level. Such strong n-type doping further supports the quantum confinement of electrons and the formation of the 2DEG.
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Affiliation(s)
- Geoffroy Kremer
- Université Paris-Saclay, CNRS, Centre de Nanosciences et de Nanotechnologies, 91120 Palaiseau, France
- Institut Jean Lamour, UMR 7198, CNRS-Université de Lorraine, Campus ARTEM, 2 allée André Guinier, BP 50840, 54011 Nancy, France
| | - Aymen Mahmoudi
- Université Paris-Saclay, CNRS, Centre de Nanosciences et de Nanotechnologies, 91120 Palaiseau, France
| | - Adel M'Foukh
- Université Paris-Saclay, CNRS, Centre de Nanosciences et de Nanotechnologies, 91120 Palaiseau, France
| | - Meryem Bouaziz
- Université Paris-Saclay, CNRS, Centre de Nanosciences et de Nanotechnologies, 91120 Palaiseau, France
| | - Mehrdad Rahimi
- Université Paris Cité, Laboratoire Matériaux et Phénomènes Quantiques, CNRS, UMR 7162, 75013 Paris, France
| | - Maria Luisa Della Rocca
- Université Paris Cité, Laboratoire Matériaux et Phénomènes Quantiques, CNRS, UMR 7162, 75013 Paris, France
| | - Patrick Le Fèvre
- SOLEIL Synchrotron, L'Orme des Merisiers, Départementale 128, F-91190 Saint-Aubin,France
| | - Jean-Francois Dayen
- Université de Strasbourg, IPCMS-CNRS UMR 7504, 23 Rue du Loess, 67034 Strasbourg, France
- Institut Universitaire de France, 1 rue Descartes, 75231 Cedex 05 Paris, France
| | - François Bertran
- SOLEIL Synchrotron, L'Orme des Merisiers, Départementale 128, F-91190 Saint-Aubin,France
| | - Sylvia Matzen
- Université Paris-Saclay, CNRS, Centre de Nanosciences et de Nanotechnologies, 91120 Palaiseau, France
| | - Marco Pala
- Université Paris-Saclay, CNRS, Centre de Nanosciences et de Nanotechnologies, 91120 Palaiseau, France
| | - Julien Chaste
- Université Paris-Saclay, CNRS, Centre de Nanosciences et de Nanotechnologies, 91120 Palaiseau, France
| | - Fabrice Oehler
- Université Paris-Saclay, CNRS, Centre de Nanosciences et de Nanotechnologies, 91120 Palaiseau, France
| | - Abdelkarim Ouerghi
- Université Paris-Saclay, CNRS, Centre de Nanosciences et de Nanotechnologies, 91120 Palaiseau, France
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8
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Trama M, Cataudella V, Perroni CA, Romeo F, Citro R. Effect of Confinement and Coulomb Interactions on the Electronic Structure of the (111) LaAlO 3/SrTiO 3 Interface. NANOMATERIALS (BASEL, SWITZERLAND) 2023; 13:819. [PMID: 36903699 PMCID: PMC10005189 DOI: 10.3390/nano13050819] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/17/2023] [Revised: 02/13/2023] [Accepted: 02/20/2023] [Indexed: 06/18/2023]
Abstract
A tight binding supercell approach is used for the calculation of the electronic structure of the (111) LaAlO3/SrTiO3 interface. The confinement potential at the interface is evaluated solving a discrete Poisson equation by means of an iterative method. In addition to the effect of the confinement, local Hubbard electron-electron terms are included at the mean-field level within a fully self-consistent procedure. The calculation carefully describes how the two-dimensional electron gas arises from the quantum confinement of electrons near the interface due to the band bending potential. The resulting electronic sub-bands and Fermi surfaces show full agreement with the electronic structure determined by angle-resolved photoelectron spectroscopy experiments. In particular, we analyse how the effect of local Hubbard interactions change the density distribution over the layers from the interface to the bulk. Interestingly, the two-dimensional electron gas at the interface is not depleted by local Hubbard interactions which indeed induce an enhancement of the electron density between the first layers and the bulk.
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Affiliation(s)
- Mattia Trama
- Physics Department “E.R. Caianiello”, Universitá degli Studi di Salerno, Via Giovanni Paolo II, 132, I-84084 Fisciano, Italy
- INFN—Sezione di Napoli, Complesso Universitario Monte S. Angelo, I-80126 Naples, Italy
- Institute for Theoretical Solid State Physics, IFW Dresden, Helmholtzstr. 20, 01069 Dresden, Germany
| | - Vittorio Cataudella
- Physics Department “Ettore Pancini”, Universitá degli Studi di Napoli “Federico II”, Complesso Universitario Monte S. Angelo, Via Cintia, I-80126 Naples, Italy
- CNR-SPIN Napoli Unit, Complesso Universitario Monte S. Angelo, Via Cintia, I-80126 Naples, Italy
| | - Carmine Antonio Perroni
- Physics Department “Ettore Pancini”, Universitá degli Studi di Napoli “Federico II”, Complesso Universitario Monte S. Angelo, Via Cintia, I-80126 Naples, Italy
- CNR-SPIN Napoli Unit, Complesso Universitario Monte S. Angelo, Via Cintia, I-80126 Naples, Italy
| | - Francesco Romeo
- Physics Department “E.R. Caianiello”, Universitá degli Studi di Salerno, Via Giovanni Paolo II, 132, I-84084 Fisciano, Italy
| | - Roberta Citro
- Physics Department “E.R. Caianiello”, Universitá degli Studi di Salerno, Via Giovanni Paolo II, 132, I-84084 Fisciano, Italy
- INFN—Sezione di Napoli, Complesso Universitario Monte S. Angelo, I-80126 Naples, Italy
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9
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Yi H, Hu LH, Wang Y, Xiao R, Cai J, Hickey DR, Dong C, Zhao YF, Zhou LJ, Zhang R, Richardella AR, Alem N, Robinson JA, Chan MHW, Xu X, Samarth N, Liu CX, Chang CZ. Crossover from Ising- to Rashba-type superconductivity in epitaxial Bi 2Se 3/monolayer NbSe 2 heterostructures. NATURE MATERIALS 2022; 21:1366-1372. [PMID: 36302957 DOI: 10.1038/s41563-022-01386-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/11/2022] [Accepted: 09/21/2022] [Indexed: 06/16/2023]
Abstract
A topological insulator (TI) interfaced with an s-wave superconductor has been predicted to host topological superconductivity. Although the growth of epitaxial TI films on s-wave superconductors has been achieved by molecular-beam epitaxy, it remains an outstanding challenge for synthesizing atomically thin TI/superconductor heterostructures, which are critical for engineering the topological superconducting phase. Here we used molecular-beam epitaxy to grow Bi2Se3 films with a controlled thickness on monolayer NbSe2 and performed in situ angle-resolved photoemission spectroscopy and ex situ magnetotransport measurements on these heterostructures. We found that the emergence of Rashba-type bulk quantum-well bands and spin-non-degenerate surface states coincides with a marked suppression of the in-plane upper critical magnetic field of the superconductivity in Bi2Se3/monolayer NbSe2 heterostructures. This is a signature of a crossover from Ising- to Rashba-type superconducting pairings, induced by altering the Bi2Se3 film thickness. Our work opens a route for exploring a robust topological superconducting phase in TI/Ising superconductor heterostructures.
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Affiliation(s)
- Hemian Yi
- Department of Physics, The Pennsylvania State University, University Park, PA, USA
| | - Lun-Hui Hu
- Department of Physics, The Pennsylvania State University, University Park, PA, USA
| | - Yuanxi Wang
- Department of Physics, The Pennsylvania State University, University Park, PA, USA
- Department of Physics, University of North Texas, Denton, TX, USA
| | - Run Xiao
- Department of Physics, The Pennsylvania State University, University Park, PA, USA
| | - Jiaqi Cai
- Department of Physics, University of Washington, Seattle, WA, USA
| | - Danielle Reifsnyder Hickey
- Department of Chemistry, The Pennsylvania State University, University Park, PA, USA
- Department of Materials Science and Engineering, The Pennsylvania State University, University Park, PA, USA
| | - Chengye Dong
- Department of Materials Science and Engineering, The Pennsylvania State University, University Park, PA, USA
| | - Yi-Fan Zhao
- Department of Physics, The Pennsylvania State University, University Park, PA, USA
| | - Ling-Jie Zhou
- Department of Physics, The Pennsylvania State University, University Park, PA, USA
| | - Ruoxi Zhang
- Department of Physics, The Pennsylvania State University, University Park, PA, USA
| | | | - Nasim Alem
- Department of Materials Science and Engineering, The Pennsylvania State University, University Park, PA, USA
| | - Joshua A Robinson
- Department of Materials Science and Engineering, The Pennsylvania State University, University Park, PA, USA
| | - Moses H W Chan
- Department of Physics, The Pennsylvania State University, University Park, PA, USA
| | - Xiaodong Xu
- Department of Physics, University of Washington, Seattle, WA, USA
- Department of Materials Science and Engineering, University of Washington, Seattle, WA, USA
| | - Nitin Samarth
- Department of Physics, The Pennsylvania State University, University Park, PA, USA
| | - Chao-Xing Liu
- Department of Physics, The Pennsylvania State University, University Park, PA, USA
| | - Cui-Zu Chang
- Department of Physics, The Pennsylvania State University, University Park, PA, USA.
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10
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Optical manipulation of Rashba-split 2-dimensional electron gas. Nat Commun 2022; 13:3096. [PMID: 35654938 PMCID: PMC9163084 DOI: 10.1038/s41467-022-30742-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2021] [Accepted: 05/16/2022] [Indexed: 11/17/2022] Open
Abstract
In spintronics, the two main approaches to actively control the electrons’ spin involve static magnetic or electric fields. An alternative avenue relies on the use of optical fields to generate spin currents, which can bolster spin-device performance, allowing for faster and more efficient logic. To date, research has mainly focused on the optical injection of spin currents through the photogalvanic effect, and little is known about the direct optical control of the intrinsic spin-splitting. To explore the optical manipulation of a material’s spin properties, we consider the Rashba effect. Using time- and angle-resolved photoemission spectroscopy (TR-ARPES), we demonstrate that an optical excitation can tune the Rashba-induced spin splitting of a two-dimensional electron gas at the surface of Bi2Se3. We establish that light-induced photovoltage and charge carrier redistribution - which in concert modulate the Rashba spin-orbit coupling strength on a sub-picosecond timescale - can offer an unprecedented platform for achieving optically-driven spin logic devices. The major challenge for the development of spin based information processing is to obtain efficient ways of controlling spin. Here, Michiardi et al show that the Rashba spin-splitting at the surface of Bi2Se3 topological insulator can be controlled via optical pulses on picosecond timescales.
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11
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Chen X, Wang H, Liu H, Wang C, Wei G, Fang C, Wang H, Geng C, Liu S, Li P, Yu H, Zhao W, Miao J, Li Y, Wang L, Nie T, Zhao J, Wu X. Generation and Control of Terahertz Spin Currents in Topology-Induced 2D Ferromagnetic Fe 3 GeTe 2 |Bi 2 Te 3 Heterostructures. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2022; 34:e2106172. [PMID: 34816497 DOI: 10.1002/adma.202106172] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/07/2021] [Revised: 11/10/2021] [Indexed: 06/13/2023]
Abstract
Future information technologies for low-dissipation quantum computation, high-speed storage, and on-chip communication applications require the development of atomically thin, ultracompact, and ultrafast spintronic devices in which information is encoded, stored, and processed using electron spin. Exploring low-dimensional magnetic materials, designing novel heterostructures, and generating and controlling ultrafast electron spin in 2D magnetism at room temperature, preferably in the unprecedented terahertz (THz) regime, is in high demand. Using THz emission spectroscopy driven by femtosecond laser pulses, optical THz spin-current bursts at room temperature in the 2D van der Waals ferromagnetic Fe3 GeTe2 (FGT) integrated with Bi2 Te3 as a topological insulator are successfully realized. The symmetry of the THz radiation is effectively controlled by the optical pumping incidence and external magnetic field directions, indicating that the THz generation mechanism is the inverse Edelstein effect contributed spin-to-charge conversion. Thickness-, temperature-, and structure-dependent nontrivial THz transients reveal that topology-enhanced interlayer exchange coupling increases the FGT Curie temperature to room temperature, which provides an effective approach for engineering THz spin-current pulses. These results contribute to the goal of all-optical generation, manipulation, and detection of ultrafast THz spin currents in room-temperature 2D magnetism, accelerating the development of atomically thin high-speed spintronic devices.
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Affiliation(s)
- Xinhou Chen
- School of Electronic and Information Engineering, Beihang University, Beijing, 100191, China
| | - Hangtian Wang
- Fert Beijing Institute, MIIT Key Laboratory of Spintronics, School of Integrated Circuit Science and Engineering, Beihang University, Beijing, 100191, China
| | - Haijiang Liu
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
| | - Chun Wang
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Gaoshuai Wei
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Chan Fang
- Fert Beijing Institute, MIIT Key Laboratory of Spintronics, School of Integrated Circuit Science and Engineering, Beihang University, Beijing, 100191, China
| | - Hanchen Wang
- Fert Beijing Institute, MIIT Key Laboratory of Spintronics, School of Integrated Circuit Science and Engineering, Beihang University, Beijing, 100191, China
| | - Chunyan Geng
- School of Electronic and Information Engineering, Beihang University, Beijing, 100191, China
| | - Shaojie Liu
- School of Cyber Science and Technology, Beihang University, Beijing, 100191, China
| | - Peiyan Li
- School of Electronic and Information Engineering, Beihang University, Beijing, 100191, China
| | - Haiming Yu
- Fert Beijing Institute, MIIT Key Laboratory of Spintronics, School of Integrated Circuit Science and Engineering, Beihang University, Beijing, 100191, China
| | - Weisheng Zhao
- Fert Beijing Institute, MIIT Key Laboratory of Spintronics, School of Integrated Circuit Science and Engineering, Beihang University, Beijing, 100191, China
- Hefei Innovation Research Institute, Beihang University, Hefei, 230013, China
| | - Jungang Miao
- School of Electronic and Information Engineering, Beihang University, Beijing, 100191, China
| | - Yutong Li
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China
- Songshan Lake Materials Laboratory, Dongguan, 523808, China
| | - Li Wang
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
| | - Tianxiao Nie
- Fert Beijing Institute, MIIT Key Laboratory of Spintronics, School of Integrated Circuit Science and Engineering, Beihang University, Beijing, 100191, China
- Hefei Innovation Research Institute, Beihang University, Hefei, 230013, China
| | - Jimin Zhao
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China
- Songshan Lake Materials Laboratory, Dongguan, 523808, China
| | - Xiaojun Wu
- School of Electronic and Information Engineering, Beihang University, Beijing, 100191, China
- School of Cyber Science and Technology, Beihang University, Beijing, 100191, China
- Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan, 430074, China
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12
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Ko W, Gai Z, Puretzky AA, Liang L, Berlijn T, Hachtel JA, Xiao K, Ganesh P, Yoon M, Li AP. Understanding Heterogeneities in Quantum Materials. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2022:e2106909. [PMID: 35170112 DOI: 10.1002/adma.202106909] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/31/2021] [Revised: 02/08/2022] [Indexed: 06/14/2023]
Abstract
Quantum materials are usually heterogeneous, with structural defects, impurities, surfaces, edges, interfaces, and disorder. These heterogeneities are sometimes viewed as liabilities within conventional systems; however, their electronic and magnetic structures often define and affect the quantum phenomena such as coherence, interaction, entanglement, and topological effects in the host system. Therefore, a critical need is to understand the roles of heterogeneities in order to endow materials with new quantum functions for energy and quantum information science applications. In this article, several representative examples are reviewed on the recent progress in connecting the heterogeneities to the quantum behaviors of real materials. Specifically, three intertwined topic areas are assessed: i) Reveal the structural, electronic, magnetic, vibrational, and optical degrees of freedom of heterogeneities. ii) Understand the effect of heterogeneities on the behaviors of quantum states in host material systems. iii) Control heterogeneities for new quantum functions. This progress is achieved by establishing the atomistic-level structure-property relationships associated with heterogeneities in quantum materials. The understanding of the interactions between electronic, magnetic, photonic, and vibrational states of heterogeneities enables the design of new quantum materials, including topological matter and quantum light emitters based on heterogenous 2D materials.
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Affiliation(s)
- Wonhee Ko
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee, 37831, USA
| | - Zheng Gai
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee, 37831, USA
| | - Alexander A Puretzky
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee, 37831, USA
| | - Liangbo Liang
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee, 37831, USA
| | - Tom Berlijn
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee, 37831, USA
| | - Jordan A Hachtel
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee, 37831, USA
| | - Kai Xiao
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee, 37831, USA
| | - Panchapakesan Ganesh
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee, 37831, USA
| | - Mina Yoon
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, 37831, USA
| | - An-Ping Li
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee, 37831, USA
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13
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Zhang J, Yang Z, Liu S, Xia W, Zhu T, Chen C, Wang C, Wang M, Mo SK, Yang L, Kou X, Guo Y, Zhang H, Liu Z, Chen Y. Direct Visualization and Manipulation of Tunable Quantum Well State in Semiconducting Nb 2SiTe 4. ACS NANO 2021; 15:15850-15857. [PMID: 34644492 DOI: 10.1021/acsnano.1c03666] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Quantum well states (QWSs) can form at the surface or interfaces of materials with confinement potential. They have broad applications in electronic and optical devices such as high mobility electron transistor, photodetector, and quantum well laser. The properties of the QWSs are usually the key factors for the performance of the devices. However, direct visualization and manipulation of such states are, in general, challenging. In this work, by using angle-resolved photoemission spectroscopy (ARPES) and scanning tunneling microscopy/spectroscopy (STM/STS), we directly probe the QWSs generated on the vacuum interface of a narrow band gap semiconductor Nb2SiTe4. Interestingly, the position and splitting of QWSs could be easily manipulated via potassium (K) dosage onto the sample surface. Our results suggest Nb2SiTe4 to be an intriguing semiconductor system to study and engineer the QWSs, which has great potential in device applications.
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Affiliation(s)
- Jing Zhang
- School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Zhilong Yang
- National Laboratory of Solid-State Microstructures, School of Physics and Collaborative Innovation Centre of Advanced Microstructures, Nanjing University, Nanjing, 210093, China
| | - Shuai Liu
- School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, China
- University of Chinese Academy of Sciences, Beijing 100049, China
- Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800, China
| | - Wei Xia
- School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, China
- ShanghaiTech Laboratory for Topological Physics, Shanghai 201210, China
| | - Tongshuai Zhu
- National Laboratory of Solid-State Microstructures, School of Physics and Collaborative Innovation Centre of Advanced Microstructures, Nanjing University, Nanjing, 210093, China
| | - Cheng Chen
- School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, China
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Chengwei Wang
- School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, China
- University of Chinese Academy of Sciences, Beijing 100049, China
- Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050, China
| | - Meixiao Wang
- School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, China
- ShanghaiTech Laboratory for Topological Physics, Shanghai 201210, China
| | - Sung-Kwan Mo
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Lexian Yang
- State Key Laboratory of Low Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
| | - Xufeng Kou
- ShanghaiTech Laboratory for Topological Physics, Shanghai 201210, China
- School of Information Science and Technology, ShanghaiTech University, Shanghai 201210, China
| | - Yanfeng Guo
- School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, China
| | - Haijun Zhang
- National Laboratory of Solid-State Microstructures, School of Physics and Collaborative Innovation Centre of Advanced Microstructures, Nanjing University, Nanjing, 210093, China
| | - Zhongkai Liu
- School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, China
- ShanghaiTech Laboratory for Topological Physics, Shanghai 201210, China
| | - Yulin Chen
- School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, China
- ShanghaiTech Laboratory for Topological Physics, Shanghai 201210, China
- State Key Laboratory of Low Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
- Department of Physics, University of Oxford, Oxford, OX1 3PU, U.K
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14
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Glinka YD, He T, Sun XW. Dynamic Opening of a Gap in Dirac Surface States of the Thin-Film 3D Topological Insulator Bi 2Se 3 Driven by the Dynamic Rashba Effect. J Phys Chem Lett 2021; 12:5593-5600. [PMID: 34109792 DOI: 10.1021/acs.jpclett.1c01601] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Optical control of Dirac surface states (SS) in topological insulators (TI) remains one of the most challenging problems governing their potential applications in novel electronic and spintronic devices. Here, using visible-range transient absorption spectroscopy exploiting ∼340 nm (∼3.65 eV) pumping, we provide evidence for dynamic opening of a gap in the Dirac SS of the thin-film 3D TI Bi2Se3, which has been induced by the dynamic Rashba effect occurring in the film bulk with increasing optical pumping power (photoexcited carrier density). The observed effect appears through the transient absorption band associated with inverse-bremsstrahlung-type free carrier absorption in the gapped Dirac SS. We have also recognized experimental signatures of the existence of the higher energy Dirac SS in the 3D TI Bi2Se3 (in addition to those known as SS1 and SS2) with energies of ∼2.7 and ∼3.9 eV (SS3 and SS4). It is evidenced that the dynamic gap opening has the same effect on the Dirac SS occurring at any energy.
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Affiliation(s)
- Yuri D Glinka
- Guangdong University Key Lab for Advanced Quantum Dot Displays and Lighting, Shenzhen Key Laboratory for Advanced Quantum Dot Displays and Lighting, Department of Electrical and Electronic Engineering, Southern University of Science and Technology, Shenzhen 518055, China
- Institute of Physics, National Academy of Sciences of Ukraine, Kiev 03028, Ukraine
| | - Tingchao He
- College of Physics and Energy, Shenzhen University, Shenzhen 518060, China
| | - Xiao Wei Sun
- Guangdong University Key Lab for Advanced Quantum Dot Displays and Lighting, Shenzhen Key Laboratory for Advanced Quantum Dot Displays and Lighting, Department of Electrical and Electronic Engineering, Southern University of Science and Technology, Shenzhen 518055, China
- Shenzhen Planck Innovation Technologies Pte Ltd., Longgang, Shenzhen 518112, China
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15
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Park H, Jeong K, Maeng I, Sim KI, Pathak S, Kim J, Hong SB, Jung TS, Kang C, Kim JH, Hong J, Cho MH. Enhanced Spin-to-Charge Conversion Efficiency in Ultrathin Bi 2Se 3 Observed by Spintronic Terahertz Spectroscopy. ACS APPLIED MATERIALS & INTERFACES 2021; 13:23153-23160. [PMID: 33945256 DOI: 10.1021/acsami.1c03168] [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
Owing to their remarkable spin-charge conversion (SCC) efficiency, topological insulators (TIs) are the most attractive candidates for spin-orbit torque generators. The simple method of enhancing SCC efficiency is to reduce the thickness of TI films to minimize the trivial bulk contribution. However, when the thickness reaches the ultrathin regime, the SCC efficiency decreases owing to intersurface hybridization. To overcome these contrary effects, we induced dehybridization of the ultrathin TI film by breaking the inversion symmetry between surfaces. For the TI film grown on an oxygen-deficient transition-metal oxide, the unbonded transition-metal d-orbitals affected only the bottom surface, resulting in asymmetric surface band structures. Spintronic terahertz emission spectroscopy, an emerging tool for investigating the SCC characteristics, revealed that the resulting SCC efficiency in symmetry-broken ultrathin Bi2Se3 was enhanced by up to ∼2.4 times.
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Affiliation(s)
- Hanbum Park
- Department of Physics, Yonsei University, Seoul 03722, Republic of Korea
| | - Kwangsik Jeong
- Department of Physics, Yonsei University, Seoul 03722, Republic of Korea
- Division of Physics and Semiconductor Science, Dongguk University, Seoul 04620, Republic of Korea
| | - InHee Maeng
- YUHS-KRIBB, Medical Convergence Research Institute, College of Medicine, Yonsei University, Seoul 03722, Republic of Korea
| | - Kyung Ik Sim
- Department of Physics, Yonsei University, Seoul 03722, Republic of Korea
- Center for Integrated Nanostructure Physics (CINAP), Institute for Basic Science (IBS), Suwon 16419, Republic of Korea
| | - Sachin Pathak
- Department of Physics, School of Engineering, University of Petroleum and Energy Studies, Dehradun 248007, Uttarakhand, India
- Department of Materials Science and Engineering, Yonsei University, Seoul 03722, Republic of Korea
| | - Jonghoon Kim
- Department of Physics, Yonsei University, Seoul 03722, Republic of Korea
| | - Seok-Bo Hong
- Department of Physics, Yonsei University, Seoul 03722, Republic of Korea
| | - Taek Sun Jung
- Department of Physics, Yonsei University, Seoul 03722, Republic of Korea
| | - Chul Kang
- Advanced Photonics Research Institute, Gwangju Institute of Science and Technology, Gwangju 61005, Republic of Korea
| | - Jae Hoon Kim
- Department of Physics, Yonsei University, Seoul 03722, Republic of Korea
| | - Jongill Hong
- Department of Materials Science and Engineering, Yonsei University, Seoul 03722, Republic of Korea
| | - Mann-Ho Cho
- Department of Physics, Yonsei University, Seoul 03722, Republic of Korea
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16
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Dai J, Frantzeskakis E, Aryal N, Chen KW, Fortuna F, Rault JE, Le Fèvre P, Balicas L, Miyamoto K, Okuda T, Manousakis E, Baumbach RE, Santander-Syro AF. Experimental Observation and Spin Texture of Dirac Node Arcs in Tetradymite Topological Metals. PHYSICAL REVIEW LETTERS 2021; 126:196407. [PMID: 34047592 DOI: 10.1103/physrevlett.126.196407] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/15/2020] [Revised: 03/08/2021] [Accepted: 04/15/2021] [Indexed: 06/12/2023]
Abstract
We report the observation of a nontrivial spin texture in Dirac node arcs, i.e., novel topological objects formed when Dirac cones of massless particles extend along an open one-dimensional line in momentum space. We find that such states are present in all the compounds of the tetradymite M_{2}Te_{2}X family (M=Ti, Zr, or Hf and X=P or As) regardless of the weak or strong character of the topological invariant. The Dirac node arcs in tetradymites are thus the simplest possible textbook example of a type-I Dirac system with a single spin-polarized node arc.
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Affiliation(s)
- J Dai
- Université Paris-Saclay, CNRS, Institut des Sciences Moléculaires d'Orsay, 91405 Orsay, France
| | - E Frantzeskakis
- Université Paris-Saclay, CNRS, Institut des Sciences Moléculaires d'Orsay, 91405 Orsay, France
| | - N Aryal
- National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32306, USA
- Department of Physics, Florida State University, Tallahassee, Florida 32306, USA
| | - K-W Chen
- National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32306, USA
- Department of Physics, Florida State University, Tallahassee, Florida 32306, USA
| | - F Fortuna
- Université Paris-Saclay, CNRS, Institut des Sciences Moléculaires d'Orsay, 91405 Orsay, France
| | - J E Rault
- Synchrotron SOLEIL, L'Orme des Merisiers, Saint-Aubin-BP48, 91192 Gif-sur-Yvette, France
| | - P Le Fèvre
- Synchrotron SOLEIL, L'Orme des Merisiers, Saint-Aubin-BP48, 91192 Gif-sur-Yvette, France
| | - L Balicas
- National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32306, USA
- Department of Physics, Florida State University, Tallahassee, Florida 32306, USA
| | - K Miyamoto
- National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32306, USA
- Department of Physics, Florida State University, Tallahassee, Florida 32306, USA
| | - T Okuda
- Hiroshima Synchrotron Radiation Center (HSRC), Hiroshima University, 2-313 Kagamiyama, Higashi-Hiroshima 739-0046, Japan
| | - E Manousakis
- National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32306, USA
- Department of Physics, Florida State University, Tallahassee, Florida 32306, USA
- Department of Physics, National and Kapodistrian University of Athens, Panepistimioupolis, Zografos, 157 84 Athens, Greece
| | - R E Baumbach
- National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32306, USA
- Department of Physics, Florida State University, Tallahassee, Florida 32306, USA
| | - A F Santander-Syro
- Université Paris-Saclay, CNRS, Institut des Sciences Moléculaires d'Orsay, 91405 Orsay, France
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17
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Hedayat H, Bugini D, Yi H, Chen C, Zhou X, Cerullo G, Dallera C, Carpene E. Ultrafast evolution of bulk, surface and surface resonance states in photoexcited [Formula: see text]. Sci Rep 2021; 11:4924. [PMID: 33649414 PMCID: PMC7921141 DOI: 10.1038/s41598-021-83848-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2020] [Accepted: 02/05/2021] [Indexed: 11/09/2022] Open
Abstract
We use circular dichroism (CD) in time- and angle-resolved photoemission spectroscopy (trARPES) to measure the femtosecond charge dynamics in the topological insulator (TI) [Formula: see text]. We detect clear CD signatures from topological surface states (TSS) and surface resonance (SR) states. In time-resolved measurements, independently from the pump polarization or intensity, the CD shows a dynamics which provides access to the unexplored electronic evolution in unoccupied states of [Formula: see text]. In particular, we are able to disentangle the unpolarized electron dynamics in the bulk states from the spin-textured TSS and SR states on the femtosecond timescale. Our study demonstrates that photoexcitation mainly involves the bulk states and is followed by sub-picosecond transport to the surface. This provides essential details on intra- and interband scattering in the relaxation process of TSS and SR states. Our results reveal the significant role of SRs in the subtle ultrafast interaction between bulk and surface states of TIs.
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Affiliation(s)
- Hamoon Hedayat
- IFN-CNR, Dipartimento di Fisica, Politecnico di Milano, 20133 Milan, Italy
- Dipartimento di Fisica, Politecnico di Milano, 20133 Milan, Italy
| | - Davide Bugini
- Dipartimento di Fisica, Politecnico di Milano, 20133 Milan, Italy
| | - Hemian Yi
- National Lab for Superconductivity, Institute of Physics, Chinese Academy of Science, Beijing, 100190 China
| | - Chaoyu Chen
- National Lab for Superconductivity, Institute of Physics, Chinese Academy of Science, Beijing, 100190 China
| | - Xingjiang Zhou
- National Lab for Superconductivity, Institute of Physics, Chinese Academy of Science, Beijing, 100190 China
| | - Giulio Cerullo
- Dipartimento di Fisica, Politecnico di Milano, 20133 Milan, Italy
| | - Claudia Dallera
- Dipartimento di Fisica, Politecnico di Milano, 20133 Milan, Italy
| | - Ettore Carpene
- IFN-CNR, Dipartimento di Fisica, Politecnico di Milano, 20133 Milan, Italy
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18
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Koo HC, Kim SB, Kim H, Park TE, Choi JW, Kim KW, Go G, Oh JH, Lee DK, Park ES, Hong IS, Lee KJ. Rashba Effect in Functional Spintronic Devices. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2020; 32:e2002117. [PMID: 32930418 DOI: 10.1002/adma.202002117] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/27/2020] [Revised: 05/28/2020] [Indexed: 06/11/2023]
Abstract
Exploiting spin transport increases the functionality of electronic devices and enables such devices to overcome physical limitations related to speed and power. Utilizing the Rashba effect at the interface of heterostructures provides promising opportunities toward the development of high-performance devices because it enables electrical control of the spin information. Herein, the focus is mainly on progress related to the two most compelling devices that exploit the Rashba effect: spin transistors and spin-orbit torque devices. For spin field-effect transistors, the gate-voltage manipulation of the Rashba effect and subsequent control of the spin precession are discussed, including for all-electric spin field-effect transistors. For spin-orbit torque devices, recent theories and experiments on interface-generated spin current are discussed. The future directions of manipulating the Rashba effect to realize fully integrated spin logic and memory devices are also discussed.
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Affiliation(s)
- Hyun Cheol Koo
- Center for Spintronics, Korea Institute of Science and Technology, Seoul, 02792, South Korea
- KU-KIST Graduate School of Converging Science and Technology, Korea University, Seoul, 02841, South Korea
| | - Seong Been Kim
- Center for Spintronics, Korea Institute of Science and Technology, Seoul, 02792, South Korea
- KU-KIST Graduate School of Converging Science and Technology, Korea University, Seoul, 02841, South Korea
| | - Hansung Kim
- Center for Spintronics, Korea Institute of Science and Technology, Seoul, 02792, South Korea
- KU-KIST Graduate School of Converging Science and Technology, Korea University, Seoul, 02841, South Korea
| | - Tae-Eon Park
- Center for Spintronics, Korea Institute of Science and Technology, Seoul, 02792, South Korea
| | - Jun Woo Choi
- Center for Spintronics, Korea Institute of Science and Technology, Seoul, 02792, South Korea
| | - Kyoung-Whan Kim
- Center for Spintronics, Korea Institute of Science and Technology, Seoul, 02792, South Korea
| | - Gyungchoon Go
- Department of Materials Science and Engineering, Korea University, Seoul, 02841, South Korea
| | - Jung Hyun Oh
- Department of Materials Science and Engineering, Korea University, Seoul, 02841, South Korea
| | - Dong-Kyu Lee
- Department of Materials Science and Engineering, Korea University, Seoul, 02841, South Korea
| | - Eun-Sang Park
- Center for Spintronics, Korea Institute of Science and Technology, Seoul, 02792, South Korea
- KU-KIST Graduate School of Converging Science and Technology, Korea University, Seoul, 02841, South Korea
| | - Ik-Sun Hong
- KU-KIST Graduate School of Converging Science and Technology, Korea University, Seoul, 02841, South Korea
| | - Kyung-Jin Lee
- KU-KIST Graduate School of Converging Science and Technology, Korea University, Seoul, 02841, South Korea
- Department of Materials Science and Engineering, Korea University, Seoul, 02841, South Korea
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19
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Sun R, Yang S, Yang X, Kumar A, Vetter E, Xue W, Li Y, Li N, Li Y, Zhang S, Ge B, Zhang XQ, He W, Kemper AF, Sun D, Cheng ZH. Visualizing Tailored Spin Phenomena in a Reduced-Dimensional Topological Superlattice. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2020; 32:e2005315. [PMID: 33145825 DOI: 10.1002/adma.202005315] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/05/2020] [Revised: 09/27/2020] [Indexed: 06/11/2023]
Abstract
Emergent topological insulators (TIs) and their design are in high demand for manipulating and transmitting spin information toward ultralow-power-consumption spintronic applications. Here, distinct topological states with tailored spin properties can be achieved in a single reduced-dimensional TI-superlattice, (Bi2 /Bi2 Se3 )-(Bi2 /Bi2 Se3 )N or (□/Bi2 Se3 )-(Bi2 /Bi2 Se3 )N (N is the repeating unit, □ represents an empty layer) by controlling the termination via molecular beam epitaxy. The Bi2 -terminated superlattice exhibits a single Dirac cone with a spin momentum splitting ≈0.5 Å-1 , producing a pronounced inverse Edelstein effect with a coherence length up to 1.26 nm. In contrast, the Bi2 Se3 -terminated superlattice is identified as a dual TI protected by coexisting time reversal and mirror symmetries, showing an unexpectedly long spin lifetime up to 1 ns. The work elucidates the key role of dimensionality and dual topological phases in selecting desired spin properties, suggesting a promise route for engineering topological superlattices for high-performance TI-spintronic devices.
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Affiliation(s)
- Rui Sun
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Shijia Yang
- Department of Physics, North Carolina State University, Raleigh, NC, 27695, USA
| | - Xu Yang
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China
| | - A Kumar
- Department of Physics, North Carolina State University, Raleigh, NC, 27695, USA
| | - Eric Vetter
- Department of Physics, North Carolina State University, Raleigh, NC, 27695, USA
- Department of Materials Science and Engineering, North Carolina State University, Raleigh, NC 27695, USA
| | - Wenhua Xue
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
| | - Yan Li
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Na Li
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Yang Li
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Shihao Zhang
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
| | - Binghui Ge
- Key Laboratory of Structure and Functional Regulation of Hybrid Materials of Ministry of Education, Institutes of Physical Science and Information Technology, Anhui University, Hefei, 230601, China
| | - Xiang-Qun Zhang
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
| | - Wei He
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
| | - Alexander F Kemper
- Department of Physics, North Carolina State University, Raleigh, NC, 27695, USA
| | - Dali Sun
- Department of Physics, North Carolina State University, Raleigh, NC, 27695, USA
- Organic and Carbon Electronics Lab (ORaCEL), North Carolina State University, Raleigh, NC, 27695, USA
| | - Zhao-Hua Cheng
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China
- Songshan Lake Materials Laboratory, Dongguan, 523808, China
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20
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Deep tuning of photo-thermoelectricity in topological surface states. Sci Rep 2020; 10:16761. [PMID: 33028944 PMCID: PMC7541493 DOI: 10.1038/s41598-020-73950-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2020] [Accepted: 09/22/2020] [Indexed: 11/08/2022] Open
Abstract
Three-dimensional topological insulators have been demonstrated in recent years, which possess intriguing gapless, spin-polarized Dirac states with linear dispersion only on the surface. The spin polarization of the topological surface states is also locked to its momentum, which allows controlling motion of electrons using optical helicity, i.e., circularly polarized light. The electrical and thermal transport can also be significantly tuned by the helicity-control of surface state electrons. Here, we report studies of photo-thermoelectric effect of the topological surface states in Bi2Te2Se thin films with large tunability using varied gate voltages and optical helicity. The Seebeck coefficient can be altered by more than five times compared to the case without spin injection. This deep tuning is originated from the optical helicity-induced photocurrent which is shown to be enhanced, reduced, turned off, and even inverted due to the change of the accessed band structures by electrical gating. The helicity-selected topological surface state thus has a large effect on thermoelectric transport, demonstrating great opportunities for realizing helicity control of optoelectronic and thermal devices.
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21
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Holtgrewe K, Mahatha SK, Sheverdyaeva PM, Moras P, Flammini R, Colonna S, Ronci F, Papagno M, Barla A, Petaccia L, Aliev ZS, Babanly MB, Chulkov EV, Sanna S, Hogan C, Carbone C. Topologization of β-antimonene on Bi 2Se 3 via proximity effects. Sci Rep 2020; 10:14619. [PMID: 32884112 PMCID: PMC7471962 DOI: 10.1038/s41598-020-71624-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2020] [Accepted: 08/19/2020] [Indexed: 11/09/2022] Open
Abstract
Topological surface states usually emerge at the boundary between a topological and a conventional insulator. Their precise physical character and spatial localization depend on the complex interplay between the chemical, structural and electronic properties of the two insulators in contact. Using a lattice-matched heterointerface of single and double bilayers of β-antimonene and bismuth selenide, we perform a comprehensive experimental and theoretical study of the chiral surface states by means of microscopy and spectroscopic measurements complemented by first-principles calculations. We demonstrate that, although β-antimonene is a trivial insulator in its free-standing form, it inherits the unique symmetry-protected spin texture from the substrate via a proximity effect that induces outward migration of the topological state. This "topologization" of β-antimonene is found to be driven by the hybridization of the bands from either side of the interface.
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Affiliation(s)
- K Holtgrewe
- Institut für Theoretische Physik and Center for Materials Research (LaMa), Justus-Liebig-Universität Gießen, Heinrich-Buff-Ring 16, 35392, Gießen, Germany
| | - S K Mahatha
- Istituto di Struttura Della Materia, Consiglio Nazionale Delle Ricerche, 34149, Trieste, Italy.
- Ruprecht Haensel Laboratory, Deutsches Elektronen-Synchrotron DESY, 22607, Hamburg, Germany.
| | - P M Sheverdyaeva
- Istituto di Struttura Della Materia, Consiglio Nazionale Delle Ricerche, 34149, Trieste, Italy
| | - P Moras
- Istituto di Struttura Della Materia, Consiglio Nazionale Delle Ricerche, 34149, Trieste, Italy
| | - R Flammini
- Istituto di Struttura Della Materia, Consiglio Nazionale Delle Ricerche, Via del Fosso del Cavaliere 100, 00133, Roma, Italy
| | - S Colonna
- Istituto di Struttura Della Materia, Consiglio Nazionale Delle Ricerche, Via del Fosso del Cavaliere 100, 00133, Roma, Italy
| | - F Ronci
- Istituto di Struttura Della Materia, Consiglio Nazionale Delle Ricerche, Via del Fosso del Cavaliere 100, 00133, Roma, Italy
| | - M Papagno
- Dipartimento di Fisica, CS, Università Della Calabria, Via P. Bucci, 87036, Arcavacata di Rende, Italy
| | - A Barla
- Istituto di Struttura Della Materia, Consiglio Nazionale Delle Ricerche, 34149, Trieste, Italy
| | - L Petaccia
- Elettra Sincrotrone Trieste, Strada Statale 14 km 163.5, 34149, Trieste, Italy
| | - Z S Aliev
- Azerbaijan State Oil and Industry University, AZ1010, Baku, Azerbaijan
| | - M B Babanly
- Institute Catalysis and Inorganic Chemistry, Azerbaijan National Academy of Science, AZ1143, Baku, Azerbaijan
| | - E V Chulkov
- Departamento de Fisica de Materiales, UPV/EHU, 20080, Donostia-San Sebastian, Basque Country, Spain
- Donostia International Physics Center (DIPC), P. de Manuel Lardizabal 4, 20018, San Sebastián, Basque Country, Spain
- Saint Petersburg State University, 198504, Saint Petersburg, Russia
- Institute of Strength Physics and Materials Science, Russian Academy of Sciences, 634021, Tomsk, Russia
| | - S Sanna
- Institut für Theoretische Physik and Center for Materials Research (LaMa), Justus-Liebig-Universität Gießen, Heinrich-Buff-Ring 16, 35392, Gießen, Germany
| | - C Hogan
- Istituto di Struttura Della Materia, Consiglio Nazionale Delle Ricerche, Via del Fosso del Cavaliere 100, 00133, Roma, Italy
| | - C Carbone
- Istituto di Struttura Della Materia, Consiglio Nazionale Delle Ricerche, 34149, Trieste, Italy
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22
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Lee KW, Lee CE. Surface reconstruction and band bending in hydrogen-adsorbed [Formula: see text] topological insulator. Sci Rep 2020; 10:14504. [PMID: 32879378 PMCID: PMC7468134 DOI: 10.1038/s41598-020-71398-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2020] [Accepted: 08/11/2020] [Indexed: 11/09/2022] Open
Abstract
We have investigated the effects of hydrogen adsorption on the [Formula: see text] topological insulator by using the density functional theory calculations. We found that hydrogen adsorption on the surface leads to surface reconstruction to reduce the band bending effect. Contrasting to a previous report that hydrogen adsorption transforms the single Dirac cone at the Brillouin zone center into three Dirac cones at the zone boundary, the Dirac cones at the zone center corresponding to the topological surface states were confirmed to be robust against the hydrogen adsorption and surface reconstruction. Hydrogen adsorption induces a Rashba-like spin-splitting of the topological surface state, and can introduce Rashba-like quantum well states within the bulk gap, which can be attributed to a semiconductor-like band bending at an interface.
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Affiliation(s)
- Kyu Won Lee
- Department of Physics, Korea University, Seoul, 02841 Republic of Korea
| | - Cheol Eui Lee
- Department of Physics, Korea University, Seoul, 02841 Republic of Korea
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23
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Bonell F, Goto M, Sauthier G, Sierra JF, Figueroa AI, Costache MV, Miwa S, Suzuki Y, Valenzuela SO. Control of Spin-Orbit Torques by Interface Engineering in Topological Insulator Heterostructures. NANO LETTERS 2020; 20:5893-5899. [PMID: 32584582 DOI: 10.1021/acs.nanolett.0c01850] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
(Bi1-xSbx)2Te3 topological insulators (TIs) are gathering increasing attention owing to their large charge-to-spin conversion efficiency and the ensuing spin-orbit torques (SOTs) that can be used to manipulate the magnetization of a ferromagnet (FM). The origin of the torques, however, remains elusive, while the implications of hybridized states and the strong material intermixing at the TI/FM interface are essentially unexplored. By combining interface chemical analysis and spin-transfer ferromagnetic resonance (ST-FMR) measurements, we demonstrate that intermixing plays a critical role in the generation of SOTs. By inserting a suitable normal metal spacer, material intermixing is reduced and the TI properties at the interface are largely improved, resulting in strong variations in the nature of the SOTs. A dramatic enhancement of a field-like torque, opposing and surpassing the Oersted-field torque, is observed, which can be attributed to the non-equilibrium spin density in Rashba-split surface bands and to the suppression of spin memory loss. These phenomena can play a relevant role at other interfaces, such as those comprising transition metal dichalcogenides.
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Affiliation(s)
- Frédéric Bonell
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC, and The Barcelona Institute of Science and Technology (BIST), Campus UAB, Bellaterra, 08193 Barcelona, Spain
| | - Minori Goto
- Graduate School of Engineering Science and Center for Spintronics Research Network (CSRN), Osaka University, Toyonaka, Osaka 560-8531, Japan
| | - Guillaume Sauthier
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC, and The Barcelona Institute of Science and Technology (BIST), Campus UAB, Bellaterra, 08193 Barcelona, Spain
| | - Juan F Sierra
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC, and The Barcelona Institute of Science and Technology (BIST), Campus UAB, Bellaterra, 08193 Barcelona, Spain
| | - Adriana I Figueroa
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC, and The Barcelona Institute of Science and Technology (BIST), Campus UAB, Bellaterra, 08193 Barcelona, Spain
| | - Marius V Costache
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC, and The Barcelona Institute of Science and Technology (BIST), Campus UAB, Bellaterra, 08193 Barcelona, Spain
| | - Shinji Miwa
- Graduate School of Engineering Science and Center for Spintronics Research Network (CSRN), Osaka University, Toyonaka, Osaka 560-8531, Japan
| | - Yoshishige Suzuki
- Graduate School of Engineering Science and Center for Spintronics Research Network (CSRN), Osaka University, Toyonaka, Osaka 560-8531, Japan
| | - Sergio O Valenzuela
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC, and The Barcelona Institute of Science and Technology (BIST), Campus UAB, Bellaterra, 08193 Barcelona, Spain
- Institució Catalana de Recerca i Estudis Avançats (ICREA), 08070 Barcelona, Spain
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24
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Stehno MP, Ngabonziza P, Myoren H, Brinkman A. Josephson Effect and Charge Distribution in Thin Bi 2 Te 3 Topological Insulators. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2020; 32:e1908351. [PMID: 32091158 DOI: 10.1002/adma.201908351] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/20/2019] [Revised: 01/24/2020] [Indexed: 06/10/2023]
Abstract
Thin layers of topological insulator materials are quasi-2D systems featuring a complex interplay between quantum confinement and topological band structure. To understand the role of the spatial distribution of carriers in electrical transport, the Josephson effect, magnetotransport, and weak anti-localization are studied in bottom-gated thin Bi2 Te3 topological insulator films. The experimental carrier densities are compared to a model based on the solutions of the self-consistent Schrödinger-Poisson equations and they are in excellent agreement. The modeling allows for a quantitative interpretation of the weak antilocalization correction to the conduction and of the critical current of Josephson junctions with weak links made from such films without any ad hoc assumptions.
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Affiliation(s)
- Martin P Stehno
- Faculty of Science and Technology and MESA+ Institute for Nanotechnology, University of Twente, 7500 AE, Enschede, The Netherlands
- Physikalisches Institut EP3, University of Würzburg, Am Hubland, 97070, Würzburg, Germany
| | - Prosper Ngabonziza
- Faculty of Science and Technology and MESA+ Institute for Nanotechnology, University of Twente, 7500 AE, Enschede, The Netherlands
- Max Planck Institute for Solid State Research, 70569, Stuttgart, Germany
- Department of Physics, University of Johannesburg, P.O. Box 524 Auckland Park, 2006, Johannesburg, South Africa
| | - Hiroaki Myoren
- Graduate school of Science and Engineering, Saitama University, 255 Shimo-Okubo, Sakura-ku, Saitama, 338-8570, Japan
| | - Alexander Brinkman
- Faculty of Science and Technology and MESA+ Institute for Nanotechnology, University of Twente, 7500 AE, Enschede, The Netherlands
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25
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From Photoemission Microscopy to an “All-in-One” Photoemission Experiment. E-JOURNAL OF SURFACE SCIENCE AND NANOTECHNOLOGY 2020. [DOI: 10.1380/ejssnt.2020.48] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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26
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Chen W. Edelstein and inverse Edelstein effects caused by the pristine surface states of topological insulators. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2020; 32:035809. [PMID: 31546243 DOI: 10.1088/1361-648x/ab46c6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
The Edelstein effect caused by the pristine surface states of three-dimensional topological insulators is investigated by means of a semiclassical approach. The combined effect of random impurity scattering and the spin-momentum locking of the gapless Dirac cone yields a current-induced surface spin accumulation that depends on the surface cleanliness, but is independent from chemical potential and temperature. Through combing the semiclassical approach with the Bloch equation, the inverse Edelstein effect that converts the spin pumping spin current into a charge current is well explained, and the conversion efficiency [Formula: see text] is revealed to be independent from the disorder. Consistency of these results with various experiments is elaborated in detail.
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Affiliation(s)
- Wei Chen
- Department of Physics, PUC-Rio, Rio de Janeiro 22451-900, Brazil
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27
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Hricovini K, Richter MC, Heckmann O, Nicolaï L, Mariot JM, Minár J. Topological electronic structure and Rashba effect in Bi thin layers: theoretical predictions and experiments. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2019; 31:283001. [PMID: 30933942 DOI: 10.1088/1361-648x/ab1529] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
The goal of the present review is to cross-compare theoretical predictions with selected experimental results on bismuth thin films exhibiting topological properties and a strong Rashba effect. The theoretical prediction that a single free-standing Bi(1 1 1) bilayer is a topological insulator has triggered a large series of studies of ultrathin Bi(1 1 1) films grown on various substrates. Using selected examples we review theoretical predictions of atomic and electronic structure of Bi thin films exhibiting topological properties due to interaction with a substrate. We also survey experimental signatures of topological surface states and Rashba effect, as obtained mostly by angle- and spin-resolved photoelectron spectroscopy.
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Affiliation(s)
- K Hricovini
- Laboratoire de Physique des Matériaux et des Surfaces, Université de Cergy-Pontoise, 5 mail Gay-Lussac, 95031 Cergy-Pontoise, France. DRF, IRAMIS, SPEC-CNRS/UMR 3680, Bât. 772, L'Orme des Merisiers, CEA Saclay, 91191 Gif-sur-Yvette Cedex, France
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28
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Plucinski L. Band structure engineering in 3D topological insulators. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2019; 31:183001. [PMID: 30731442 DOI: 10.1088/1361-648x/ab052c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
The discovery of novel topological phases has revolutionized the way we think about electronic matter. Topologically protected states have been demonstrated for many materials, however, creating materials that exhibit desired properties often remains a challenge. For example, one of the key challenges in three dimensional topological insulators has been the realization of insulating bulk, such that the unique properties of surface states could be fully employed in electron transport applications. Further challenges are in creating materials that simultaneously exhibit states protected by various symmetries on their different surfaces, inducing magnetic exchange coupling into the topological materials, as well as potentially creating non-trivial transient electronic states. This review presents theoretical concepts and a selection of experimental results from the point view of a spectroscopist, and as such might be useful for physicists who want to get familiar with the key concepts in a self-contained form with formalism reduced to readily understandable concepts.
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Affiliation(s)
- L Plucinski
- Peter Grünberg Institut PGI-6, Forschungszentrum Jülich, D-52425 Jülich, Germany. Jülich Aachen Research Alliance-Fundamentals of Future Information Technologies (JARA-FIT), 52425 Jülich, Germany
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29
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On the understanding of current-induced spin polarization of three-dimensional topological insulators. Nat Commun 2019; 10:1461. [PMID: 30931922 PMCID: PMC6443799 DOI: 10.1038/s41467-019-09271-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2018] [Accepted: 02/28/2019] [Indexed: 11/12/2022] Open
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30
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Mooshammer F, Sandner F, Huber MA, Zizlsperger M, Weigand H, Plankl M, Weyrich C, Lanius M, Kampmeier J, Mussler G, Grützmacher D, Boland JL, Cocker TL, Huber R. Nanoscale Near-Field Tomography of Surface States on (Bi 0.5Sb 0.5) 2Te 3. NANO LETTERS 2018; 18:7515-7523. [PMID: 30419748 DOI: 10.1021/acs.nanolett.8b03008] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Three-dimensional topological insulators (TIs) have attracted tremendous interest for their possibility to host massless Dirac Fermions in topologically protected surface states (TSSs), which may enable new kinds of high-speed electronics. However, recent reports have outlined the importance of band bending effects within these materials, which results in an additional two-dimensional electron gas (2DEG) with finite mass at the surface. TI surfaces are also known to be highly inhomogeneous on the nanoscale, which is masked in conventional far-field studies. Here, we use near-field microscopy in the mid-infrared spectral range to probe the local surface properties of custom-tailored (Bi0.5Sb0.5)2Te3 structures with nanometer precision in all three spatial dimensions. Applying nanotomography and nanospectroscopy, we reveal a few-nanometer-thick layer of high surface conductivity and retrieve its local dielectric function without assuming any model for the spectral response. This allows us to directly distinguish between different types of surface states. An intersubband transition within the massive 2DEG formed by quantum confinement in the bent conduction band manifests itself as a sharp, surface-bound, Lorentzian-shaped resonance. An additional broadband background in the imaginary part of the dielectric function may be caused by the TSS. Tracing the intersubband resonance with nanometer spatial precision, we observe changes of its frequency, likely originating from local variations of doping or/and the mixing ratio between Bi and Sb. Our results highlight the importance of studying the surfaces of these novel materials on the nanoscale to directly access the local optical and electronic properties via the dielectric function.
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Affiliation(s)
- Fabian Mooshammer
- Department of Physics , University of Regensburg , 93040 Regensburg , Germany
| | - Fabian Sandner
- Department of Physics , University of Regensburg , 93040 Regensburg , Germany
| | - Markus A Huber
- Department of Physics , University of Regensburg , 93040 Regensburg , Germany
| | - Martin Zizlsperger
- Department of Physics , University of Regensburg , 93040 Regensburg , Germany
| | - Helena Weigand
- Department of Physics , University of Regensburg , 93040 Regensburg , Germany
| | - Markus Plankl
- Department of Physics , University of Regensburg , 93040 Regensburg , Germany
| | - Christian Weyrich
- Peter Grünberg Institut 9 , Forschungszentrum Jülich & JARA Jülich-Aachen Research Alliance , 52425 Jülich , Germany
| | - Martin Lanius
- Peter Grünberg Institut 9 , Forschungszentrum Jülich & JARA Jülich-Aachen Research Alliance , 52425 Jülich , Germany
| | - Jörn Kampmeier
- Peter Grünberg Institut 9 , Forschungszentrum Jülich & JARA Jülich-Aachen Research Alliance , 52425 Jülich , Germany
| | - Gregor Mussler
- Peter Grünberg Institut 9 , Forschungszentrum Jülich & JARA Jülich-Aachen Research Alliance , 52425 Jülich , Germany
| | - Detlev Grützmacher
- Peter Grünberg Institut 9 , Forschungszentrum Jülich & JARA Jülich-Aachen Research Alliance , 52425 Jülich , Germany
| | - Jessica L Boland
- Department of Physics , University of Regensburg , 93040 Regensburg , Germany
| | - Tyler L Cocker
- Department of Physics and Astronomy , Michigan State University , East Lansing , Michigan 48824 , United States
| | - Rupert Huber
- Department of Physics , University of Regensburg , 93040 Regensburg , Germany
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31
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Dc M, Grassi R, Chen JY, Jamali M, Reifsnyder Hickey D, Zhang D, Zhao Z, Li H, Quarterman P, Lv Y, Li M, Manchon A, Mkhoyan KA, Low T, Wang JP. Room-temperature high spin-orbit torque due to quantum confinement in sputtered Bi xSe (1-x) films. NATURE MATERIALS 2018; 17:800-807. [PMID: 30061733 DOI: 10.1038/s41563-018-0136-z] [Citation(s) in RCA: 94] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/04/2017] [Accepted: 06/21/2018] [Indexed: 05/17/2023]
Abstract
The spin-orbit torque (SOT) that arises from materials with large spin-orbit coupling promises a path for ultralow power and fast magnetic-based storage and computational devices. We investigated the SOT from magnetron-sputtered BixSe(1-x) thin films in BixSe(1-x)/Co20Fe60B20 heterostructures by using d.c. planar Hall and spin-torque ferromagnetic resonance (ST-FMR) methods. Remarkably, the spin torque efficiency (θS) was determined to be as large as 18.62 ± 0.13 and 8.67 ± 1.08 using the d.c. planar Hall and ST-FMR methods, respectively. Moreover, switching of the perpendicular CoFeB multilayers using the SOT from the BixSe(1-x) was observed at room temperature with a low critical magnetization switching current density of 4.3 × 105 A cm-2. Quantum transport simulations using a realistic sp3 tight-binding model suggests that the high SOT in sputtered BixSe(1-x) is due to the quantum confinement effect with a charge-to-spin conversion efficiency that enhances with reduced size and dimensionality. The demonstrated θS, ease of growth of the films on a silicon substrate and successful growth and switching of perpendicular CoFeB multilayers on BixSe(1-x) films provide an avenue for the use of BixSe(1-x) as a spin density generator in SOT-based memory and logic devices.
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Affiliation(s)
- Mahendra Dc
- School of Physics and Astronomy, University of Minnesota, Minneapolis, MN, USA
| | - Roberto Grassi
- Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, MN, USA
| | - Jun-Yang Chen
- Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, MN, USA
| | - Mahdi Jamali
- Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, MN, USA
| | | | - Delin Zhang
- Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, MN, USA
| | - Zhengyang Zhao
- Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, MN, USA
| | - Hongshi Li
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, MN, USA
| | - P Quarterman
- Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, MN, USA
| | - Yang Lv
- Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, MN, USA
| | - Mo Li
- Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, MN, USA
| | - Aurelien Manchon
- King Abdullah University of Science and Technology (KAUST), Physical Science and Engineering Division (PSE), Thuwal, Saudi Arabia
- King Abdullah University of Science and Technology (KAUST), Computer, Electrical and Mathematical Sciences and Engineering Division (CEMSE), Thuwal, Saudi Arabia
| | - K Andre Mkhoyan
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, MN, USA
| | - Tony Low
- Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, MN, USA
| | - Jian-Ping Wang
- School of Physics and Astronomy, University of Minnesota, Minneapolis, MN, USA.
- Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, MN, USA.
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, MN, USA.
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32
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Gou J, Kong LJ, Li WB, Sheng SX, Li H, Meng S, Cheng P, Wu KH, Chen L. Scanning tunneling microscopy investigations of unoccupied surface states in two-dimensional semiconducting β-√3 × √3-Bi/Si(111) surface. Phys Chem Chem Phys 2018; 20:20188-20193. [PMID: 30027957 DOI: 10.1039/c8cp01356j] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Two-dimensional surface structures often host a surface state in the bulk gap, which plays a crucial role in the surface electron transport. The diversity of in-gap surface states extends the category of two-dimensional systems and gives us more choices in material applications. In this article, we investigated the surface states of β-√3 × √3-Bi/Si(111) surface by scanning tunneling microscopy. Two nearly free electron states in the bulk gap of silicon were found in the unoccupied states. Combined with first-principles calculations, these two states were verified to be the Bi-contributed surface states and electron-accumulation-induced quantum well states. Due to the spin-orbit coupling of Bi atoms, Bi-contributed surface states exhibit free-electron Rashba splitting. The in-gap surface states with spin splitting can possibly be used for spin polarized electronics applications.
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Affiliation(s)
- Jian Gou
- Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China.
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33
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Iyer V, Chen YP, Xu X. Ultrafast Surface State Spin-Carrier Dynamics in the Topological Insulator Bi_{2}Te_{2}Se. PHYSICAL REVIEW LETTERS 2018; 121:026807. [PMID: 30085694 DOI: 10.1103/physrevlett.121.026807] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/14/2018] [Revised: 05/06/2018] [Indexed: 06/08/2023]
Abstract
Topological insulators are promising candidates for optically driven spintronic devices, because photoexcitation of spin polarized surface states is governed by angular momentum selection rules. We carry out femtosecond midinfrared spectroscopy on thin films of the topological insulator Bi_{2}Te_{2}Se, which has a higher surface state conductivity compared to conventionally studied Bi_{2}Se_{3} and Bi_{2}Te_{3}. Both charge and spin dynamics are probed utilizing circularly polarized light. With a sub-band-gap excitation, clear helicity-dependent dynamics is observed only in thin (<20 nm) flakes. On the other hand, such dependence is observed for both thin and thick flakes with above-band-gap excitation. The helicity dependence is attributed to asymmetric excitation of the Dirac-like surface states. The observed long-lasting asymmetry over 10 ps even at room temperature indicates low backscattering of surface state carriers which can be exploited for spintronic devices.
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Affiliation(s)
- Vasudevan Iyer
- Department of Mechanical Engineering and Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, USA
| | - Yong P Chen
- Department of Physics and Astronomy and School of Electrical and Computer Engineering and Birck Nanotechnology Center and Purdue Quantum Center, Purdue University, West Lafayette, Indiana 47907, USA
| | - Xianfan Xu
- Department of Mechanical Engineering and Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, USA
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34
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Li CH, van 't Erve OMJ, Yan C, Li L, Jonker BT. Electrical Detection of Charge-to-spin and Spin-to-Charge Conversion in a Topological Insulator Bi 2Te 3 Using BN/Al 2O 3 Hybrid Tunnel Barrier. Sci Rep 2018; 8:10265. [PMID: 29980749 PMCID: PMC6035191 DOI: 10.1038/s41598-018-28547-y] [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: 02/02/2018] [Accepted: 06/18/2018] [Indexed: 11/18/2022] Open
Abstract
One of the most striking properties of three-dimensional topological insulators (TIs) is spin-momentum locking, where the spin is locked at right angles to momentum and hence an unpolarized charge current creates a net spin polarization. Alternatively, if a net spin is injected into the TI surface state system, it is distinctively associated with a unique carrier momentum and hence should generate a charge accumulation, as in the so-called inverse Edelstein effect. Here using a Fe/Al2O3/BN tunnel barrier, we demonstrate both effects in a single device in Bi2Te3: the electrical detection of the spin accumulation generated by an unpolarized current flowing through the surface states, and that of the charge accumulation generated by spins injected into the surface state system. This work is the first to utilize BN as part of a hybrid tunnel barrier on TI, where we observed a high spin polarization of 93% for the TI surfaces states. The reverse spin-to-charge measurement is an independent confirmation that spin and momentum are locked in the surface states of TI, and offers additional avenues for spin manipulation. It further demonstrates the robustness and versatility of electrical access to the spin system within TI surface states, an important step towards its utilization in TI-based spintronics devices.
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Affiliation(s)
- C H Li
- Materials Science and Technology Division, Naval Research Laboratory, Washington, DC, 20375, USA.
| | - O M J van 't Erve
- Materials Science and Technology Division, Naval Research Laboratory, Washington, DC, 20375, USA
| | - C Yan
- Department of Physics and Astronomy, West Virginia University, Morgantown, WV, 26506, USA
| | - L Li
- Department of Physics and Astronomy, West Virginia University, Morgantown, WV, 26506, USA
| | - B T Jonker
- Materials Science and Technology Division, Naval Research Laboratory, Washington, DC, 20375, USA
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35
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Liu Y, Besbas J, Wang Y, He P, Chen M, Zhu D, Wu Y, Lee JM, Wang L, Moon J, Koirala N, Oh S, Yang H. Direct visualization of current-induced spin accumulation in topological insulators. Nat Commun 2018; 9:2492. [PMID: 29950680 PMCID: PMC6021425 DOI: 10.1038/s41467-018-04939-6] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2017] [Accepted: 06/07/2018] [Indexed: 11/08/2022] Open
Abstract
Charge-to-spin conversion in various materials is the key for the fundamental understanding of spin-orbitronics and efficient magnetization manipulation. Here we report the direct spatial imaging of current-induced spin accumulation at the channel edges of Bi2Se3 and BiSbTeSe2 topological insulators as well as Pt by a scanning photovoltage microscope at room temperature. The spin polarization is along the out-of-plane direction with opposite signs for the two channel edges. The accumulated spin direction reverses sign upon changing the current direction and the detected spin signal shows a linear dependence on the magnitude of currents, indicating that our observed phenomena are current-induced effects. The spin Hall angle of Bi2Se3, BiSbTeSe2, and Pt is determined to be 0.0085, 0.0616, and 0.0085, respectively. Our results open up the possibility of optically detecting the current-induced spin accumulations, and thus point towards a better understanding of the interaction between spins and circularly polarized light.
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Affiliation(s)
- Yang Liu
- Department of Electrical and Computer Engineering, National University of Singapore, Singapore, 117576, Singapore
| | - Jean Besbas
- Department of Electrical and Computer Engineering, National University of Singapore, Singapore, 117576, Singapore
| | - Yi Wang
- Department of Electrical and Computer Engineering, National University of Singapore, Singapore, 117576, Singapore
| | - Pan He
- Department of Electrical and Computer Engineering, National University of Singapore, Singapore, 117576, Singapore
| | - Mengji Chen
- Department of Electrical and Computer Engineering, National University of Singapore, Singapore, 117576, Singapore
| | - Dapeng Zhu
- Department of Electrical and Computer Engineering, National University of Singapore, Singapore, 117576, Singapore
| | - Yang Wu
- Department of Electrical and Computer Engineering, National University of Singapore, Singapore, 117576, Singapore
| | - Jong Min Lee
- Department of Electrical and Computer Engineering, National University of Singapore, Singapore, 117576, Singapore
| | - Lan Wang
- RMIT University, School of Science, Department of Physics, Melbourne, VIC, 3001, Australia
| | - Jisoo Moon
- Department of Physics and Astronomy, Rutgers, The State University of New Jersey, Piscataway, NJ, 08854, USA
| | - Nikesh Koirala
- Department of Physics and Astronomy, Rutgers, The State University of New Jersey, Piscataway, NJ, 08854, USA
| | - Seongshik Oh
- Department of Physics and Astronomy, Rutgers, The State University of New Jersey, Piscataway, NJ, 08854, USA
| | - Hyunsoo Yang
- Department of Electrical and Computer Engineering, National University of Singapore, Singapore, 117576, Singapore.
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36
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Alexander-Webber JA, Huang J, Beilsten-Edmands J, Čermák P, Drašar Č, Nicholas RJ, Coldea AI. Multi-band magnetotransport in exfoliated thin films of Cu x Bi 2Se 3. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2018; 30:155302. [PMID: 29469818 DOI: 10.1088/1361-648x/aab193] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
We report magnetotransport studies in thin (<100 nm) exfoliated films of Cu x Bi2Se3 and we detect an unusual electronic transition at low temperatures. Bulk crystals show weak superconductivity with [Formula: see text] K and a possible electronic phase transition around 200 K. Following exfoliation, superconductivity is supressed and a strongly temperature dependent multi-band conductivity is observed for T < 30 K. This transition between competing conducting channels may be enhanced due to the presence of electronic ordering, and could be affected by the presence of an effective internal stress due to Cu intercalation. By fitting to the weak antilocalisation conductivity correction at low magnetic fields we confirm that the low temperature regime maintains a quantum phase coherence length [Formula: see text] nm indicating the presence of topologically protected surface states.
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Affiliation(s)
- J A Alexander-Webber
- Department of Engineering, University of Cambridge, 9 J.J. Thomson Avenue, Cambridge CB3 0FA, United Kingdom
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37
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Clark OJ, Neat MJ, Okawa K, Bawden L, Marković I, Mazzola F, Feng J, Sunko V, Riley JM, Meevasana W, Fujii J, Vobornik I, Kim TK, Hoesch M, Sasagawa T, Wahl P, Bahramy MS, King PDC. Fermiology and Superconductivity of Topological Surface States in PdTe_{2}. PHYSICAL REVIEW LETTERS 2018; 120:156401. [PMID: 29756894 DOI: 10.1103/physrevlett.120.156401] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/14/2017] [Revised: 01/17/2018] [Indexed: 05/12/2023]
Abstract
We study the low-energy surface electronic structure of the transition-metal dichalcogenide superconductor PdTe_{2} by spin- and angle-resolved photoemission, scanning tunneling microscopy, and density-functional theory-based supercell calculations. Comparing PdTe_{2} with its sister compound PtSe_{2}, we demonstrate how enhanced interlayer hopping in the Te-based material drives a band inversion within the antibonding p-orbital manifold well above the Fermi level. We show how this mediates spin-polarized topological surface states which form rich multivalley Fermi surfaces with complex spin textures. Scanning tunneling spectroscopy reveals type-II superconductivity at the surface, and moreover shows no evidence for an unconventional component of its superconducting order parameter, despite the presence of topological surface states.
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Affiliation(s)
- O J Clark
- SUPA, School of Physics and Astronomy, University of St. Andrews, St. Andrews KY16 9SS, United Kingdom
| | - M J Neat
- SUPA, School of Physics and Astronomy, University of St. Andrews, St. Andrews KY16 9SS, United Kingdom
| | - K Okawa
- Materials and Structures Laboratory, Tokyo Institute of Technology, Kanagawa 226-8503, Japan
| | - L Bawden
- SUPA, School of Physics and Astronomy, University of St. Andrews, St. Andrews KY16 9SS, United Kingdom
| | - I Marković
- SUPA, School of Physics and Astronomy, University of St. Andrews, St. Andrews KY16 9SS, United Kingdom
- Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, 01187 Dresden, Germany
| | - F Mazzola
- SUPA, School of Physics and Astronomy, University of St. Andrews, St. Andrews KY16 9SS, United Kingdom
| | - J Feng
- SUPA, School of Physics and Astronomy, University of St. Andrews, St. Andrews KY16 9SS, United Kingdom
- Suzhou Institute of Nano-Tech. and Nanobionics (SINANO), CAS, 398 Ruoshui Road, SEID, SIP, Suzhou 215123, China
| | - V Sunko
- SUPA, School of Physics and Astronomy, University of St. Andrews, St. Andrews KY16 9SS, United Kingdom
- Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, 01187 Dresden, Germany
| | - J M Riley
- SUPA, School of Physics and Astronomy, University of St. Andrews, St. Andrews KY16 9SS, United Kingdom
- Diamond Light Source, Harwell Campus, Didcot OX11 0DE, United Kingdom
| | - W Meevasana
- School of Physics and Center of Excellence on Advanced Functional Materials, Suranaree University of Technology, Nakhon Ratchasima, 30000, Thailand
- ThEP, Commission of Higher Education, Bangkok 10400, Thailand
| | - J Fujii
- Istituto Officina dei Materiali (IOM)-CNR, Laboratorio TASC, in Area Science Park, S.S.14, Km 163.5, I-34149 Trieste, Italy
| | - I Vobornik
- Istituto Officina dei Materiali (IOM)-CNR, Laboratorio TASC, in Area Science Park, S.S.14, Km 163.5, I-34149 Trieste, Italy
| | - 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
| | - T Sasagawa
- Materials and Structures Laboratory, Tokyo Institute of Technology, Kanagawa 226-8503, Japan
| | - P Wahl
- SUPA, School of Physics and Astronomy, University of St. Andrews, St. Andrews KY16 9SS, United Kingdom
| | - M S Bahramy
- Quantum-Phase Electronics Center and Department of Applied Physics, The University of Tokyo, Tokyo 113-8656, Japan
- 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 KY16 9SS, United Kingdom
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38
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Yu J, Zeng X, Zhang L, Yin C, Chen Y, Liu Y, Cheng S, Lai Y, He K, Xue Q. Inverse spin Hall effect induced by linearly polarized light in the topological insulator Bi 2Se 3. OPTICS EXPRESS 2018; 26:4832-4841. [PMID: 29475328 DOI: 10.1364/oe.26.004832] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/22/2017] [Accepted: 02/06/2018] [Indexed: 06/08/2023]
Abstract
The inverse spin Hall effect (ISHE) induced by the normal incidence of linearly-polarized infrared radiation has been observed in the topological insulator Bi2Se3. A model has been proposed to explain the phenomenon, and the spin transverse force has been determined by the model fitting. The anomalous linear photogalvanic effect (ALPGE) is also observed, and the photoinduced momentum anisotropy is extracted. Furthermore, the ISHE and ALPGE are investigated at different temperatures between 77 and 300 K, and the temperature dependence of the spin transverse force and photoinduced momentum anisotropy are obtained. This study suggests a new way to investigate the inverse spin Hall effect via linearly polarized light even at room temperature.
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39
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Fanchiang YT, Chen KHM, Tseng CC, Chen CC, Cheng CK, Yang SR, Wu CN, Lee SF, Hong M, Kwo J. Strongly exchange-coupled and surface-state-modulated magnetization dynamics in Bi 2Se 3/yttrium iron garnet heterostructures. Nat Commun 2018; 9:223. [PMID: 29335558 PMCID: PMC5768741 DOI: 10.1038/s41467-017-02743-2] [Citation(s) in RCA: 47] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2017] [Accepted: 12/20/2017] [Indexed: 12/03/2022] Open
Abstract
Harnessing the spin–momentum locking of topological surface states in conjunction with magnetic materials is the first step to realize novel topological insulator-based devices. Here, we report strong interfacial coupling in Bi2Se3/yttrium iron garnet (YIG) bilayers manifested as large interfacial in-plane magnetic anisotropy (IMA) and enhancement of damping probed by ferromagnetic resonance. The interfacial IMA and damping enhancement reaches a maximum when the Bi2Se3 film approaches its two-dimensional limit, indicating that topological surface states play an important role in the magnetization dynamics of YIG. Temperature-dependent ferromagnetic resonance of Bi2Se3/YIG reveals signatures of the magnetic proximity effect of TC as high as 180 K, an emerging low-temperature perpendicular magnetic anisotropy competing the high-temperature IMA, and an increasing exchange effective field of YIG steadily increasing toward low temperature. Our study sheds light on the effects of topological insulators on magnetization dynamics, essential for the development of topological insulator-based spintronic devices. Understanding the effects of topological insulators on magnetization dynamics of adjacent magnetic materials is essential for novel spintronic devices. Here, Fanchiang et al. report thickness dependence of interfacial in-plane magnetic anisotropy and damping enhancement in Bi2Se3/yttrium iron garnet (YIG) bilayers, indicating an important role of topological surface states in the magnetization dynamics of YIG.
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Affiliation(s)
- Y T Fanchiang
- Department of Physics, National Taiwan University, Taipei, 10617, Taiwan
| | - K H M Chen
- Department of Physics, National Tsing Hua University, Hsinchu, 30013, Taiwan
| | - C C Tseng
- Department of Physics, National Tsing Hua University, Hsinchu, 30013, Taiwan
| | - C C Chen
- Department of Physics, National Tsing Hua University, Hsinchu, 30013, Taiwan
| | - C K Cheng
- Department of Physics, National Taiwan University, Taipei, 10617, Taiwan
| | - S R Yang
- Department of Physics, National Tsing Hua University, Hsinchu, 30013, Taiwan
| | - C N Wu
- Department of Physics, National Tsing Hua University, Hsinchu, 30013, Taiwan
| | - S F Lee
- Institute of Physics, Academia Sinica, Taipei, 11529, Taiwan.
| | - M Hong
- Department of Physics, National Taiwan University, Taipei, 10617, Taiwan.
| | - J Kwo
- Department of Physics, National Tsing Hua University, Hsinchu, 30013, Taiwan.
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40
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Yilmaz T, Hines W, Alraddadi S, Budnick JI, Sinkovic B. Origin of the temperature dependence of the energy gap in Cr-doped Bi 2Se 3. Phys Chem Chem Phys 2018. [DOI: 10.1039/c7cp08049b] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Recent progress in impurity-doped topological insulators has shown that the gap at the Dirac point shrinks with reducing temperature.
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Affiliation(s)
- Turgut Yilmaz
- Department of Physics, University of Connecticut
- Storrs
- USA
- Department of Physics, Science and Literature Faculty, Uludag University
- Bursa 16059
| | - William Hines
- Department of Physics, University of Connecticut
- Storrs
- USA
| | - Shoroog Alraddadi
- Department of Physics, Umm Al-Qura University
- Makkah 24382
- Kingdom of Saudi Arabia
| | | | - Boris Sinkovic
- Department of Physics, University of Connecticut
- Storrs
- USA
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41
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Yu J, Zeng X, Zhang L, He K, Cheng S, Lai Y, Huang W, Chen Y, Yin C, Xue Q. Photoinduced Inverse Spin Hall Effect of Surface States in the Topological Insulator Bi 2Se 3. NANO LETTERS 2017; 17:7878-7885. [PMID: 29141404 DOI: 10.1021/acs.nanolett.7b04172] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The three-dimensional (3D) topological insulator (TI) Bi2Se3 exhibits topologically protected, linearly dispersing Dirac surface states (SSs). To access the intriguing properties of these SSs, it is important to distinguish them from the coexisting two-dimensional electron gas (2DEG) on the surface. Here, we use circularly polarized light to induce the inverse spin Hall effect in a Bi2Se3 thin film at different temperatures (i.e., from 77 to 300 K). It is demonstrated that the photoinduced inverse spin Hall effect (PISHE) of the top SSs and the 2DEG can be separated based on their opposite signs. The temperature and power dependence of the PISHE also confirms our method. Furthermore, it is found that the PISHE in the 2DEG is dominated by the extrinsic mechanism, as revealed by the temperature dependence of the PISHE.
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Affiliation(s)
- Jinling Yu
- Institute of Micro/Nano Devices and Solar Cells, School of Physics and Information Engineering, Fuzhou University , Fuzhou 350108, Fujian, China
| | - Xiaolin Zeng
- Institute of Micro/Nano Devices and Solar Cells, School of Physics and Information Engineering, Fuzhou University , Fuzhou 350108, Fujian, China
| | - Liguo Zhang
- Department of Physics, State Key Laboratory of Low Dimensional Quantum Physics, Tsinghua University , Beijing 100084, China
| | - Ke He
- Department of Physics, State Key Laboratory of Low Dimensional Quantum Physics, Tsinghua University , Beijing 100084, China
| | - Shuying Cheng
- Institute of Micro/Nano Devices and Solar Cells, School of Physics and Information Engineering, Fuzhou University , Fuzhou 350108, Fujian, China
- Jiangsu Collaborative Innovation Center of Photovolatic Science and Engineering, Changzhou University , Changzhou 213164, Jiangsu China
| | - Yunfeng Lai
- Institute of Micro/Nano Devices and Solar Cells, School of Physics and Information Engineering, Fuzhou University , Fuzhou 350108, Fujian, China
- Jiangsu Collaborative Innovation Center of Photovolatic Science and Engineering, Changzhou University , Changzhou 213164, Jiangsu China
| | - Wei Huang
- Key Laboratory of Semiconductor Materials Science, Institute of Semiconductors, Chinese Academy of Sciences , Beijing 100083, China
| | - Yonghai Chen
- Key Laboratory of Semiconductor Materials Science, Institute of Semiconductors, Chinese Academy of Sciences , Beijing 100083, China
- College of Materials Science and Optoelectronic Technology, University of Chinese Academy of Sciences , Beijing 100049, China
| | - Chunming Yin
- School of Physics, University of New South Wales , Sydney, New South Wales 2052, Australia
- CAS Key Laboratory of Microscale Magnetic Resonance, Department of Modern Physics, Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China , Hefei 230026, China
| | - Qikun Xue
- Department of Physics, State Key Laboratory of Low Dimensional Quantum Physics, Tsinghua University , Beijing 100084, China
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42
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Wang Y, Zhu D, Wu Y, Yang Y, Yu J, Ramaswamy R, Mishra R, Shi S, Elyasi M, Teo KL, Wu Y, Yang H. Room temperature magnetization switching in topological insulator-ferromagnet heterostructures by spin-orbit torques. Nat Commun 2017; 8:1364. [PMID: 29118331 PMCID: PMC5677620 DOI: 10.1038/s41467-017-01583-4] [Citation(s) in RCA: 86] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2017] [Accepted: 09/29/2017] [Indexed: 12/24/2022] Open
Abstract
Topological insulators with spin-momentum-locked topological surface states are expected to exhibit a giant spin-orbit torque in the topological insulator/ferromagnet systems. To date, the topological insulator spin-orbit torque-driven magnetization switching is solely reported in a Cr-doped topological insulator at 1.9 K. Here we directly show giant spin-orbit torque-driven magnetization switching in a Bi2Se3/NiFe heterostructure at room temperature captured using a magneto-optic Kerr effect microscope. We identify a large charge-to-spin conversion efficiency of ~1-1.75 in the thin Bi2Se3 films, where the topological surface states are dominant. In addition, we find the current density required for the magnetization switching is extremely low, ~6 × 105 A cm-2, which is one to two orders of magnitude smaller than that with heavy metals. Our demonstration of room temperature magnetization switching of a conventional 3d ferromagnet using Bi2Se3 may lead to potential innovations in topological insulator-based spintronic applications.
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Affiliation(s)
- Yi Wang
- Department of Electrical and Computer Engineering, National University of Singapore, Singapore, 117576, Singapore
| | - Dapeng Zhu
- Department of Electrical and Computer Engineering, National University of Singapore, Singapore, 117576, Singapore
| | - Yang Wu
- Department of Electrical and Computer Engineering, National University of Singapore, Singapore, 117576, Singapore
| | - Yumeng Yang
- Department of Electrical and Computer Engineering, National University of Singapore, Singapore, 117576, Singapore
| | - Jiawei Yu
- Department of Electrical and Computer Engineering, National University of Singapore, Singapore, 117576, Singapore
| | - Rajagopalan Ramaswamy
- Department of Electrical and Computer Engineering, National University of Singapore, Singapore, 117576, Singapore
| | - Rahul Mishra
- Department of Electrical and Computer Engineering, National University of Singapore, Singapore, 117576, Singapore
| | - Shuyuan Shi
- Department of Electrical and Computer Engineering, National University of Singapore, Singapore, 117576, Singapore.,Centre for Advanced 2D Materials, National University of Singapore, 6 Science Drive 2, Singapore, 117546, Singapore
| | - Mehrdad Elyasi
- Department of Electrical and Computer Engineering, National University of Singapore, Singapore, 117576, Singapore
| | - Kie-Leong Teo
- Department of Electrical and Computer Engineering, National University of Singapore, Singapore, 117576, Singapore
| | - Yihong Wu
- Department of Electrical and Computer Engineering, National University of Singapore, Singapore, 117576, Singapore
| | - Hyunsoo Yang
- Department of Electrical and Computer Engineering, National University of Singapore, Singapore, 117576, Singapore. .,Centre for Advanced 2D Materials, National University of Singapore, 6 Science Drive 2, Singapore, 117546, Singapore.
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43
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Kim SH, Jin KH, Kho BW, Park BG, Liu F, Kim JS, Yeom HW. Atomically Abrupt Topological p-n Junction. ACS NANO 2017; 11:9671-9677. [PMID: 28825806 DOI: 10.1021/acsnano.7b03880] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Topological insulators (TI's) are a new class of quantum matter with extraordinary surface electronic states, which bear great potential for spintronics and error-tolerant quantum computing. In order to put a TI into any practical use, these materials need to be fabricated into devices whose basic units are often p-n junctions. Interesting electronic properties of a 'topological' p-n junction were proposed theoretically such as the junction electronic state and the spin rectification. However, the fabrication of a lateral topological p-n junction has been challenging because of materials, process, and fundamental reasons. Here, we demonstrate an innovative approach to realize a p-n junction of topological surface states (TSS's) of a three-dimensional (3D) topological insulator (TI) with an atomically abrupt interface. When a ultrathin Sb film is grown on a 3D TI of Bi2Se3 with a typical n-type TSS, the surface develops a strongly p-type TSS through the substantial hybridization between the 2D Sb film and the Bi2Se3 surface. Thus, the Bi2Se3 surface covered partially with Sb films bifurcates into areas of n- and p-type TSS's as separated by atomic step edges with a lateral electronic junction of as short as 2 nm. This approach opens a different avenue toward various electronic and spintronic devices based on well-defined topological p-n junctions with the scalability down to atomic dimensions.
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Affiliation(s)
- Sung Hwan Kim
- Center for Artificial Low Dimensional Electronic Systems, Institute for Basic Science (IBS) , Pohang 37673, Republic of Korea
| | - Kyung-Hwan Jin
- Department of Materials Science and Engineering, University of Utah , Salt Lake City, Utah 84112, United States
| | | | | | - Feng Liu
- Department of Materials Science and Engineering, University of Utah , Salt Lake City, Utah 84112, United States
- Collaborative Innovation Center of Quantum Matter , Beijing 100084, China
| | | | - Han Woong Yeom
- Center for Artificial Low Dimensional Electronic Systems, Institute for Basic Science (IBS) , Pohang 37673, Republic of Korea
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44
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Pan Y, Wang QZ, Yeats AL, Pillsbury T, Flanagan TC, Richardella A, Zhang H, Awschalom DD, Liu CX, Samarth N. Helicity dependent photocurrent in electrically gated (Bi 1-x Sb x ) 2Te 3 thin films. Nat Commun 2017; 8:1037. [PMID: 29051541 PMCID: PMC5648839 DOI: 10.1038/s41467-017-00711-4] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2016] [Accepted: 07/20/2017] [Indexed: 11/09/2022] Open
Abstract
Circularly polarized photons are known to generate a directional helicity-dependent photocurrent in three-dimensional topological insulators at room temperature. Surprisingly, the phenomenon is readily observed at photon energies that excite electrons to states far above the spin-momentum locked Dirac cone and the underlying mechanism for the helicity-dependent photocurrent is still not understood. Here we show a comprehensive study of the helicity-dependent photocurrent in (Bi1-x Sb x )2Te3 thin films as a function of the incidence angle of the optical excitation, its wavelength and the gate-tuned chemical potential. Our observations allow us to unambiguously identify the circular photo-galvanic effect as the dominant mechanism for the helicity-dependent photocurrent. Additionally, we use an analytical model to relate the directional nature of the photocurrent to asymmetric optical transitions between the topological surface states and bulk bands. The insights we obtain are important for engineering opto-spintronic devices that rely on optical steering of spin and charge currents.
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Affiliation(s)
- Yu Pan
- Department of Physics and Materials Research Institute, The Pennsylvania State University, University Park, PA, 16802-6300, USA
| | - Qing-Ze Wang
- Department of Physics and Materials Research Institute, The Pennsylvania State University, University Park, PA, 16802-6300, USA
| | - Andrew L Yeats
- Institute for Molecular Engineering, University of Chicago, Chicago, IL, 60637, USA
| | - Timothy Pillsbury
- Department of Physics and Materials Research Institute, The Pennsylvania State University, University Park, PA, 16802-6300, USA
| | - Thomas C Flanagan
- Department of Physics and Materials Research Institute, The Pennsylvania State University, University Park, PA, 16802-6300, USA
| | - Anthony Richardella
- Department of Physics and Materials Research Institute, The Pennsylvania State University, University Park, PA, 16802-6300, USA
| | - Haijun Zhang
- National Laboratory of Solid State Microstructures, School of Physics and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, 210093, China
| | - David D Awschalom
- Institute for Molecular Engineering, University of Chicago, Chicago, IL, 60637, USA
| | - Chao-Xing Liu
- Department of Physics and Materials Research Institute, The Pennsylvania State University, University Park, PA, 16802-6300, USA
| | - Nitin Samarth
- Department of Physics and Materials Research Institute, The Pennsylvania State University, University Park, PA, 16802-6300, USA.
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45
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Marmolejo-Tejada JM, Dolui K, Lazić P, Chang PH, Smidstrup S, Stradi D, Stokbro K, Nikolić BK. Proximity Band Structure and Spin Textures on Both Sides of Topological-Insulator/Ferromagnetic-Metal Interface and Their Charge Transport Probes. NANO LETTERS 2017; 17:5626-5633. [PMID: 28795576 DOI: 10.1021/acs.nanolett.7b02511] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The control of recently observed spintronic effects in topological-insulator/ferromagnetic-metal (TI/FM) heterostructures is thwarted by the lack of understanding of band structure and spin textures around their interfaces. Here we combine density functional theory with Green's function techniques to obtain the spectral function at any plane passing through atoms of Bi2Se3 and Co or Cu layers comprising the interface. Instead of naively assumed Dirac cone gapped by the proximity exchange field spectral function, we find that the Rashba ferromagnetic model describes the spectral function on the surface of Bi2Se3 in contact with Co near the Fermi level EF0, where circular and snowflake-like constant energy contours coexist around which spin locks to momentum. The remnant of the Dirac cone is hybridized with evanescent wave functions from metallic layers and pushed, due to charge transfer from Co or Cu layers, a few tenths of an electron-volt below EF0 for both Bi2Se3/Co and Bi2Se3/Cu interfaces while hosting distorted helical spin texture wounding around a single circle. These features explain recent observation of sensitivity of spin-to-charge conversion signal at TI/Cu interface to tuning of EF0. Crucially for spin-orbit torque in TI/FM heterostructures, few monolayers of Co adjacent to Bi2Se3 host spectral functions very different from the bulk metal, as well as in-plane spin textures (despite Co magnetization being out-of-plane) due to proximity spin-orbit coupling in Co induced by Bi2Se3. We predict that out-of-plane tunneling anisotropic magnetoresistance in Cu/Bi2Se3/Co vertical heterostructure can serve as a sensitive probe of the type of spin texture residing at EF0.
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Affiliation(s)
- Juan Manuel Marmolejo-Tejada
- Department of Physics and Astronomy, University of Delaware , Newark, Delaware 19716-2570, United States
- School of Electrical and Electronics Engineering, Universidad del Valle , Cali, AA 25360, Colombia
| | - Kapildeb Dolui
- Department of Physics and Astronomy, University of Delaware , Newark, Delaware 19716-2570, United States
| | - Predrag Lazić
- Rudjer Bošković Institute , P.O. Box 180, Bijenička c. 54, 10 002 Zagreb, Croatia
| | - Po-Hao Chang
- Department of Physics and Astronomy, University of Nebraska Lincoln , Lincoln, Nebraska 68588, United States
| | - Søren Smidstrup
- QuantumWise A/S, Fruebjergvej 3, Box 4, DK-2100 Copenhagen, Denmark
| | - Daniele Stradi
- QuantumWise A/S, Fruebjergvej 3, Box 4, DK-2100 Copenhagen, Denmark
| | - Kurt Stokbro
- QuantumWise A/S, Fruebjergvej 3, Box 4, DK-2100 Copenhagen, Denmark
| | - Branislav K Nikolić
- Department of Physics and Astronomy, University of Delaware , Newark, Delaware 19716-2570, United States
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46
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Battiato M, Aguilera I, Sánchez-Barriga J. Generalized GW+Boltzmann Approach for the Description of Ultrafast Electron Dynamics in Topological Insulators. MATERIALS 2017; 10:ma10070810. [PMID: 28773171 PMCID: PMC5551853 DOI: 10.3390/ma10070810] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/27/2017] [Revised: 06/27/2017] [Accepted: 07/11/2017] [Indexed: 11/17/2022]
Abstract
Quantum-phase transitions between trivial insulators and topological insulators differ from ordinary metal-insulator transitions in that they arise from the inversion of the bulk band structure due to strong spin–orbit coupling. Such topological phase transitions are unique in nature as they lead to the emergence of topological surface states which are characterized by a peculiar spin texture that is believed to play a central role in the generation and manipulation of dissipationless surface spin currents on ultrafast timescales. Here, we provide a generalized GW+Boltzmann approach for the description of ultrafast dynamics in topological insulators driven by electron–electron and electron–phonon scatterings. Taking the prototypical insulator Bi2Te3 as an example, we test the robustness of our approach by comparing the theoretical prediction to results of time- and angle-resolved photoemission experiments. From this comparison, we are able to demonstrate the crucial role of the excited spin texture in the subpicosecond relaxation of transient electrons, as well as to accurately obtain the magnitude and strength of electron–electron and electron–phonon couplings. Our approach could be used as a generalized theory for three-dimensional topological insulators in the bulk-conducting transport regime, paving the way for the realization of a unified theory of ultrafast dynamics in topological materials.
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Affiliation(s)
- Marco Battiato
- Institute of Solid State Physics, Vienna University of Technology, A-1040 Vienna, Austria.
| | - Irene Aguilera
- Peter Grünberg Institute and Institute for Advanced Simulation, Forschungszentrum Jülich and JARA, D-52425 Jülich, Germany.
| | - Jaime Sánchez-Barriga
- Helmholtz-Zentrum Berlin für Materialien und Energie, Albert-Einstein-Str. 15, 12489 Berlin, Germany.
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47
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Bigi C, Das PK, Benedetti D, Salvador F, Krizmancic D, Sergo R, Martin A, Panaccione G, Rossi G, Fujii J, Vobornik I. Very efficient spin polarization analysis (VESPA): new exchange scattering-based setup for spin-resolved ARPES at APE-NFFA beamline at Elettra. JOURNAL OF SYNCHROTRON RADIATION 2017; 24:750-756. [PMID: 28664881 PMCID: PMC5493025 DOI: 10.1107/s1600577517006907] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/18/2016] [Accepted: 05/08/2017] [Indexed: 05/06/2023]
Abstract
Complete photoemission experiments, enabling measurement of the full quantum set of the photoelectron final state, are in high demand for studying materials and nanostructures whose properties are determined by strong electron and spin correlations. Here the implementation of the new spin polarimeter VESPA (Very Efficient Spin Polarization Analysis) at the APE-NFFA beamline at Elettra is reported, which is based on the exchange coupling between the photoelectron spin and a ferromagnetic surface in a reflectometry setup. The system was designed to be integrated with a dedicated Scienta-Omicron DA30 electron energy analyzer allowing for two simultaneous reflectometry measurements, along perpendicular axes, that, after magnetization switching of the two targets, allow the three-dimensional vectorial reconstruction of the spin polarization to be performed while operating the DA30 in high-resolution mode. VESPA represents the very first installation for spin-resolved ARPES (SPARPES) at the Elettra synchrotron in Trieste, and is being heavily exploited by SPARPES users since autumn 2015.
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Affiliation(s)
- Chiara Bigi
- Department of Physics, Università degli Studi di Milano, I-20133 Milano, Italy
- CNR-IOM Laboratorio TASC, I-34149 Trieste, Italy
| | - Pranab K. Das
- CNR-IOM Laboratorio TASC, I-34149 Trieste, Italy
- International Centre for Theoretical Physics (ICTP), I-34151 Trieste, Italy
| | | | | | | | - Rudi Sergo
- Elettra Sincrotrone Trieste, I-34149 Trieste, Italy
| | | | | | - Giorgio Rossi
- Department of Physics, Università degli Studi di Milano, I-20133 Milano, Italy
- CNR-IOM Laboratorio TASC, I-34149 Trieste, Italy
| | - Jun Fujii
- CNR-IOM Laboratorio TASC, I-34149 Trieste, Italy
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48
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Feng YP, Shen L, Yang M, Wang A, Zeng M, Wu Q, Chintalapati S, Chang CR. Prospects of spintronics based on 2D materials. WILEY INTERDISCIPLINARY REVIEWS-COMPUTATIONAL MOLECULAR SCIENCE 2017. [DOI: 10.1002/wcms.1313] [Citation(s) in RCA: 101] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Affiliation(s)
- Yuan Ping Feng
- Department of Physics; National University of Singapore; Singapore
- Centre for Advanced Two-dimensional Materials; National University of Singapore; Singapore
| | - Lei Shen
- Department of Mechanical Engineering; National University of Singapore; Singapore
- Engineering Science Programme; National University of Singapore; Singapore
| | - Ming Yang
- Institute of Materials Science and Engineering; A*STAR; Singapore
| | - Aizhu Wang
- Department of Physics; National University of Singapore; Singapore
- Department of Electrical and Computer Engineering; National University of Singapore; Singapore
| | | | - Qingyun Wu
- Department of Materials Science and Engineering; National University of Singapore; Singapore
| | - Sandhya Chintalapati
- Centre for Advanced Two-dimensional Materials; National University of Singapore; Singapore
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49
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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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50
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Kubota Y, Murata K, Miyawaki J, Ozawa K, Onbasli MC, Shirasawa T, Feng B, Yamamoto S, Liu RY, Yamamoto S, Mahatha SK, Sheverdyaeva P, Moras P, Ross CA, Suga S, Harada Y, Wang KL, Matsuda I. Interface electronic structure at the topological insulator-ferrimagnetic insulator junction. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2017; 29:055002. [PMID: 27911879 DOI: 10.1088/1361-648x/29/5/055002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
An interface electron state at the junction between a three-dimensional topological insulator film, Bi2Se3, and a ferrimagnetic insulator film, Y3Fe5O12 (YIG), was investigated by measurements of angle-resolved photoelectron spectroscopy and x-ray absorption magnetic circular dichroism. The surface state of the Bi2Se3 film was directly observed and localized 3d spin states of the Fe3+ in the YIG film were confirmed. The proximity effect is likely described in terms of the exchange interaction between the localized Fe 3d electrons in the YIG film and delocalized electrons of the surface and bulk states in the Bi2Se3 film.
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Affiliation(s)
- Y Kubota
- Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba 277-8581, Japan
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