1
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Ok JM, Mohanta N, Zhang J, Yoon S, Okamoto S, Choi ES, Zhou H, Briggeman M, Irvin P, Lupini AR, Pai YY, Skoropata E, Sohn C, Li H, Miao H, Lawrie B, Choi WS, Eres G, Levy J, Lee HN. Correlated oxide Dirac semimetal in the extreme quantum limit. SCIENCE ADVANCES 2021; 7:eabf9631. [PMID: 34524855 PMCID: PMC8443170 DOI: 10.1126/sciadv.abf9631] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/01/2020] [Accepted: 07/23/2021] [Indexed: 05/25/2023]
Abstract
Quantum materials (QMs) with strong correlation and nontrivial topology are indispensable to next-generation information and computing technologies. Exploitation of topological band structure is an ideal starting point to realize correlated topological QMs. Here, we report that strain-induced symmetry modification in correlated oxide SrNbO3 thin films creates an emerging topological band structure. Dirac electrons in strained SrNbO3 films reveal ultrahigh mobility (μmax ≈ 100,000 cm2/Vs), exceptionally small effective mass (m* ~ 0.04me), and nonzero Berry phase. Strained SrNbO3 films reach the extreme quantum limit, exhibiting a sign of fractional occupation of Landau levels and giant mass enhancement. Our results suggest that symmetry-modified SrNbO3 is a rare example of correlated oxide Dirac semimetals, in which strong correlation of Dirac electrons leads to the realization of a novel correlated topological QM.
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Affiliation(s)
- Jong Mok Ok
- Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
| | | | - Jie Zhang
- Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
| | - Sangmoon Yoon
- Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
| | | | - Eun Sang Choi
- National High Magnetic Field Laboratory, Florida State University, Tallahassee, FL 32310, USA
| | - Hua Zhou
- Advanced Photon Source, Argonne National Laboratory, Lemont, IL 60439, USA
| | - Megan Briggeman
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA 15260, USA
- Pittsburgh Quantum Institute, Pittsburgh, PA 15260, USA
| | - Patrick Irvin
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA 15260, USA
- Pittsburgh Quantum Institute, Pittsburgh, PA 15260, USA
| | | | - Yun-Yi Pai
- Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
| | | | - Changhee Sohn
- Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
| | - Haoxiang Li
- Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
| | - Hu Miao
- Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
| | | | - Woo Seok Choi
- Department of Physics, Sungkyunkwan University, Suwon 16419, Korea
| | - Gyula Eres
- Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
| | - Jeremy Levy
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA 15260, USA
- Pittsburgh Quantum Institute, Pittsburgh, PA 15260, USA
| | - Ho Nyung Lee
- Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
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2
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Li D, Adamo C, Wang BY, Yoon H, Chen Z, Hong SS, Lu D, Cui Y, Hikita Y, Hwang HY. Stabilization of Sr 3Al 2O 6 Growth Templates for Ex Situ Synthesis of Freestanding Crystalline Oxide Membranes. NANO LETTERS 2021; 21:4454-4460. [PMID: 33989008 DOI: 10.1021/acs.nanolett.1c01194] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
A new synthetic approach has recently been developed for the fabrication of freestanding crystalline perovskite oxide nanomembranes, which involves the epitaxial growth of a water-soluble sacrificial layer. By utilizing an ultrathin capping layer of SrTiO3, here we show that this sacrificial layer, as grown by pulsed laser deposition, can be stabilized in air and therefore be used as transferrable templates for ex situ epitaxial growth using other techniques. We find that the stability of these templates depends on the thickness of the capping layer. On these templates, freestanding superconducting SrTiO3 membranes were synthesized ex situ using molecular beam epitaxy, enabled by the lower growth temperature which preserves the sacrificial layer. This study paves the way for the synthesis of an expanded selection of freestanding oxide membranes and heterostructures with a wide variety of ex situ growth techniques.
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Affiliation(s)
- Danfeng Li
- Geballe Laboratory for Advanced Materials, Stanford University, Stanford, California 94305, United States
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States
- Department of Physics, City University of Hong Kong, Kowloon, Hong Kong, China
| | - Carolina Adamo
- Geballe Laboratory for Advanced Materials, Stanford University, Stanford, California 94305, United States
| | - Bai Yang Wang
- Geballe Laboratory for Advanced Materials, Stanford University, Stanford, California 94305, United States
| | - Hyeok Yoon
- Geballe Laboratory for Advanced Materials, Stanford University, Stanford, California 94305, United States
| | - Zhuoyu Chen
- Geballe Laboratory for Advanced Materials, Stanford University, Stanford, California 94305, United States
| | - Seung Sae Hong
- Geballe Laboratory for Advanced Materials, Stanford University, Stanford, California 94305, United States
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States
| | - Di Lu
- Geballe Laboratory for Advanced Materials, Stanford University, Stanford, California 94305, United States
| | - Yi Cui
- Geballe Laboratory for Advanced Materials, Stanford University, Stanford, California 94305, United States
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States
| | - Yasuyuki Hikita
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States
| | - Harold Y Hwang
- Geballe Laboratory for Advanced Materials, Stanford University, Stanford, California 94305, United States
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States
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3
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Rischau CW, Li Y, Fauqué B, Inoue H, Kim M, Bell C, Hwang HY, Kapitulnik A, Behnia K. Universal Bound to the Amplitude of the Vortex Nernst Signal in Superconductors. PHYSICAL REVIEW LETTERS 2021; 126:077001. [PMID: 33666461 DOI: 10.1103/physrevlett.126.077001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/13/2020] [Revised: 11/05/2020] [Accepted: 01/07/2021] [Indexed: 06/12/2023]
Abstract
A liquid of superconducting vortices generates a transverse thermoelectric response. This Nernst signal has a tail deep in the normal state due to superconducting fluctuations. Here, we present a study of the Nernst effect in two-dimensional heterostructures of Nb-doped strontium titanate (STO) and in amorphous MoGe. The Nernst signal generated by ephemeral Cooper pairs above the critical temperature has the magnitude expected by theory in STO. On the other hand, the peak amplitude of the vortex Nernst signal below T_{c} is comparable in both and in numerous other superconductors despite the large distribution of the critical temperature and the critical magnetic fields. In four superconductors belonging to different families, the maximum Nernst signal corresponds to an entropy per vortex per layer of ≈k_{B}ln2.
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Affiliation(s)
- Carl Willem Rischau
- Laboratoire de Physique et d'Étude des Matériaux (ESPCI Paris-CNRS-Sorbonne Université), PSL Research University, 75005 Paris, France
| | - Yuke Li
- Laboratoire de Physique et d'Étude des Matériaux (ESPCI Paris-CNRS-Sorbonne Université), PSL Research University, 75005 Paris, France
| | - Benoît Fauqué
- JEIP, USR 3573 CNRS, Collège de France, PSL Research University, 75005 Paris, France
| | - Hisashi Inoue
- Geballe Laboratory for Advanced Materials, Stanford University, Stanford, California 94305, USA
| | - Minu Kim
- Geballe Laboratory for Advanced Materials, Stanford University, Stanford, California 94305, USA
| | - Christopher Bell
- Geballe Laboratory for Advanced Materials, Stanford University, Stanford, California 94305, USA
| | - Harold Y Hwang
- Geballe Laboratory for Advanced Materials, Stanford University, Stanford, California 94305, USA
| | - Aharon Kapitulnik
- Geballe Laboratory for Advanced Materials, Stanford University, Stanford, California 94305, USA
| | - Kamran Behnia
- Laboratoire de Physique et d'Étude des Matériaux (ESPCI Paris-CNRS-Sorbonne Université), PSL Research University, 75005 Paris, France
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4
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Chen X, Zhang T, Yu Y, Cai X, Gao T, Zhang T, Sun H, Gu C, Gu Z, Zhu Y, Zhou J, Nie Y, Pan X. Rewritable High-Mobility Electrons in Oxide Heterostructure of Layered Perovskite/Perovskite. ACS APPLIED MATERIALS & INTERFACES 2021; 13:7812-7821. [PMID: 33529011 DOI: 10.1021/acsami.1c00481] [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
Perovskite oxide SrTiO3 can be electron-doped and exhibits high mobility by introducing oxygen vacancies or dopants such as Nb or La. A reversible after-growth tuning of high mobility carriers in SrTiO3 is highly desired for the applications in high-speed electronic devices. Here, we report the observation of tunable high-mobility electrons in layered perovskite/perovskite (Srn+1TinO3n+1/SrTiO3) heterostructure. By use of Srn+1TinO3n+1 as the oxygen diffusion barrier, the oxygen vacancy concentration near the interface can be reversibly engineered by high-temperature annealing or infrared laser heating. Because of the identical elemental compositions (Sr, Ti, and O) throughout the whole heterostructure, interfacial ionic intermixing is absent, giving rise to an extremely high mobility (exceeding 55000 cm2 V-1 s-1 at 2 K) in this type of oxide heterostructure. This layered perovskite/perovskite heterostructure provides a promising platform for reconfigurable high-speed electronic devices.
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Affiliation(s)
- Xiaofeng Chen
- National Laboratory of Solid State Microstructures, Jiangsu Key Laboratory of Artificial Functional Materials, College of Engineering and Applied Sciences, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Tingting Zhang
- National Laboratory of Solid State Microstructures, Jiangsu Key Laboratory of Artificial Functional Materials, College of Engineering and Applied Sciences, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Yang Yu
- National Laboratory of Solid State Microstructures, Jiangsu Key Laboratory of Artificial Functional Materials, College of Engineering and Applied Sciences, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Xiangbin Cai
- Department of Physics, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China
| | - Tianyi Gao
- National Laboratory of Solid State Microstructures, Jiangsu Key Laboratory of Artificial Functional Materials, College of Engineering and Applied Sciences, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Tianwei Zhang
- National Laboratory of Solid State Microstructures, Jiangsu Key Laboratory of Artificial Functional Materials, College of Engineering and Applied Sciences, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Haoying Sun
- National Laboratory of Solid State Microstructures, Jiangsu Key Laboratory of Artificial Functional Materials, College of Engineering and Applied Sciences, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Chenyi Gu
- National Laboratory of Solid State Microstructures, Jiangsu Key Laboratory of Artificial Functional Materials, College of Engineering and Applied Sciences, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Zhengbin Gu
- National Laboratory of Solid State Microstructures, Jiangsu Key Laboratory of Artificial Functional Materials, College of Engineering and Applied Sciences, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Ye Zhu
- Department of Applied Physics, Research Institute for Smart Energy, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, China
| | - Jian Zhou
- National Laboratory of Solid State Microstructures, Jiangsu Key Laboratory of Artificial Functional Materials, College of Engineering and Applied Sciences, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Yuefeng Nie
- National Laboratory of Solid State Microstructures, Jiangsu Key Laboratory of Artificial Functional Materials, College of Engineering and Applied Sciences, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Xiaoqing Pan
- Department of Materials Science and Engineering, Department of Physics and Astronomy, University of California, Irvine, Irvine, California 92697, United States
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5
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Swartz AG, Cheung AKC, Yoon H, Chen Z, Hikita Y, Raghu S, Hwang HY. Superconducting Tunneling Spectroscopy of Spin-Orbit Coupling and Orbital Depairing in Nb:SrTiO_{3}. PHYSICAL REVIEW LETTERS 2018; 121:167003. [PMID: 30387624 DOI: 10.1103/physrevlett.121.167003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/12/2018] [Indexed: 06/08/2023]
Abstract
We have examined the intrinsic spin-orbit coupling and orbital depairing in thin films of Nb-doped SrTiO_{3} by superconducting tunneling spectroscopy. The orbital depairing is geometrically suppressed in the two-dimensional limit, enabling a quantitative evaluation of the Fermi level spin-orbit scattering using Maki's theory. The response of the superconducting gap under in-plane magnetic fields demonstrates short spin-orbit scattering times τ_{so}≤1.1 ps. Analysis of the orbital depairing indicates that the heavy electron band contributes significantly to pairing. These results suggest that the intrinsic spin-orbit scattering time in SrTiO_{3} is comparable to those associated with Rashba effects in SrTiO_{3} interfacial conducting layers and can be considered significant in all forms of superconductivity in SrTiO_{3}.
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Affiliation(s)
- Adrian G Swartz
- Geballe Laboratory for Advanced Materials, Stanford University, Stanford, California 94305, USA
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
- Department of Applied Physics, Stanford University, Stanford, California 94305, USA
| | - Alfred K C Cheung
- Department of Physics, Stanford University, Stanford, California 94305, USA
| | - Hyeok Yoon
- Geballe Laboratory for Advanced Materials, Stanford University, Stanford, California 94305, USA
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
- Department of Applied Physics, Stanford University, Stanford, California 94305, USA
| | - Zhuoyu Chen
- Geballe Laboratory for Advanced Materials, Stanford University, Stanford, California 94305, USA
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
- Department of Applied Physics, Stanford University, Stanford, California 94305, USA
| | - Yasuyuki Hikita
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
| | - Srinivas Raghu
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
- Department of Physics, Stanford University, Stanford, California 94305, USA
| | - Harold Y Hwang
- Geballe Laboratory for Advanced Materials, Stanford University, Stanford, California 94305, USA
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
- Department of Applied Physics, Stanford University, Stanford, California 94305, USA
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6
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Wang T, Wang X, Chen Z, Sun X, Wang P, Zheng X, Rong X, Yang L, Guo W, Wang D, Cheng J, Lin X, Li P, Li J, He X, Zhang Q, Li M, Zhang J, Yang X, Xu F, Ge W, Zhang X, Shen B. High-Mobility Two-Dimensional Electron Gas at InGaN/InN Heterointerface Grown by Molecular Beam Epitaxy. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2018; 5:1800844. [PMID: 30250812 PMCID: PMC6145405 DOI: 10.1002/advs.201800844] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/29/2018] [Indexed: 05/27/2023]
Abstract
Due to the intrinsic spontaneous and piezoelectric polarization effect, III-nitride semiconductor heterostructures are promising candidates for generating 2D electron gas (2DEG) system. Among III-nitrides, InN is predicted to be the best conductive-channel material because its electrons have the smallest effective mass and it exhibits large band offsets at the heterointerface of GaN/InN or AlN/InN. Until now, that prediction has remained theoretical, due to a giant gap between the optimal growth windows of InN and GaN, and the difficult epitaxial growth of InN in general. The experimental realization of 2DEG at an InGaN/InN heterointerface grown by molecular beam epitaxy is reported here. The directly probed electron mobility and the sheet electron density of the InGaN/InN heterostructure are determined by Hall-effect measurements at room temperature to be 2.29 × 103 cm2 V-1 s-1 and 2.14 × 1013 cm-2, respectively, including contribution from the InN bottom layer. The Shubnikov-de Haas results at 3 K confirm that the 2DEG has an electron density of 3.30 × 1012 cm-2 and a quantum mobility of 1.48 × 103 cm2 V-1 s-1. The experimental observations of 2DEG at the InGaN/InN heterointerface have paved the way for fabricating higher-speed transistors based on an InN channel.
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Affiliation(s)
- Tao Wang
- State Key Laboratory of Artificial Microstructure and Mesoscopic PhysicsSchool of PhysicsPeking UniversityBeijing100871P. R. China
- King Abdullah University of Science and TechnologyDivision of Physical Science and EngineeringThuwal23955–6900Kingdom of Saudi Arabia
| | - Xinqiang Wang
- State Key Laboratory of Artificial Microstructure and Mesoscopic PhysicsSchool of PhysicsPeking UniversityBeijing100871P. R. China
- Collaborative Innovation Center of Quantum MatterBeijing100871P. R. China
| | - Zhaoying Chen
- State Key Laboratory of Artificial Microstructure and Mesoscopic PhysicsSchool of PhysicsPeking UniversityBeijing100871P. R. China
| | - Xiaoxiao Sun
- State Key Laboratory of Artificial Microstructure and Mesoscopic PhysicsSchool of PhysicsPeking UniversityBeijing100871P. R. China
| | - Ping Wang
- State Key Laboratory of Artificial Microstructure and Mesoscopic PhysicsSchool of PhysicsPeking UniversityBeijing100871P. R. China
| | - Xiantong Zheng
- State Key Laboratory of Artificial Microstructure and Mesoscopic PhysicsSchool of PhysicsPeking UniversityBeijing100871P. R. China
| | - Xin Rong
- State Key Laboratory of Artificial Microstructure and Mesoscopic PhysicsSchool of PhysicsPeking UniversityBeijing100871P. R. China
| | - Liuyun Yang
- State Key Laboratory of Artificial Microstructure and Mesoscopic PhysicsSchool of PhysicsPeking UniversityBeijing100871P. R. China
| | - Weiwei Guo
- State Key Laboratory of Artificial Microstructure and Mesoscopic PhysicsSchool of PhysicsPeking UniversityBeijing100871P. R. China
| | - Ding Wang
- State Key Laboratory of Artificial Microstructure and Mesoscopic PhysicsSchool of PhysicsPeking UniversityBeijing100871P. R. China
- Microsystem & Terahertz Research CenterChina Academy of Engineering Physics (CAEP)Chengdu610200P. R. China
| | - Jianpeng Cheng
- State Key Laboratory of Artificial Microstructure and Mesoscopic PhysicsSchool of PhysicsPeking UniversityBeijing100871P. R. China
| | - Xi Lin
- Collaborative Innovation Center of Quantum MatterBeijing100871P. R. China
| | - Peng Li
- King Abdullah University of Science and TechnologyDivision of Physical Science and EngineeringThuwal23955–6900Kingdom of Saudi Arabia
| | - Jun Li
- King Abdullah University of Science and TechnologyDivision of Physical Science and EngineeringThuwal23955–6900Kingdom of Saudi Arabia
| | - Xin He
- King Abdullah University of Science and TechnologyDivision of Physical Science and EngineeringThuwal23955–6900Kingdom of Saudi Arabia
| | - Qiang Zhang
- King Abdullah University of Science and TechnologyDivision of Physical Science and EngineeringThuwal23955–6900Kingdom of Saudi Arabia
| | - Mo Li
- Microsystem & Terahertz Research CenterChina Academy of Engineering Physics (CAEP)Chengdu610200P. R. China
| | - Jian Zhang
- Microsystem & Terahertz Research CenterChina Academy of Engineering Physics (CAEP)Chengdu610200P. R. China
| | - Xuelin Yang
- State Key Laboratory of Artificial Microstructure and Mesoscopic PhysicsSchool of PhysicsPeking UniversityBeijing100871P. R. China
| | - Fujun Xu
- State Key Laboratory of Artificial Microstructure and Mesoscopic PhysicsSchool of PhysicsPeking UniversityBeijing100871P. R. China
| | - Weikun Ge
- State Key Laboratory of Artificial Microstructure and Mesoscopic PhysicsSchool of PhysicsPeking UniversityBeijing100871P. R. China
| | - Xixiang Zhang
- King Abdullah University of Science and TechnologyDivision of Physical Science and EngineeringThuwal23955–6900Kingdom of Saudi Arabia
| | - Bo Shen
- State Key Laboratory of Artificial Microstructure and Mesoscopic PhysicsSchool of PhysicsPeking UniversityBeijing100871P. R. China
- Collaborative Innovation Center of Quantum MatterBeijing100871P. R. China
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7
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Pai YY, Tylan-Tyler A, Irvin P, Levy J. Physics of SrTiO 3-based heterostructures and nanostructures: a review. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2018; 81:036503. [PMID: 29424362 DOI: 10.1088/1361-6633/aa892d] [Citation(s) in RCA: 51] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
This review provides a summary of the rich physics expressed within SrTiO3-based heterostructures and nanostructures. The intended audience is researchers who are working in the field of oxides, but also those with different backgrounds (e.g., semiconductor nanostructures). After reviewing the relevant properties of SrTiO3 itself, we will then discuss the basics of SrTiO3-based heterostructures, how they can be grown, and how devices are typically fabricated. Next, we will cover the physics of these heterostructures, including their phase diagram and coupling between the various degrees of freedom. Finally, we will review the rich landscape of quantum transport phenomena, as well as the devices that elicit them.
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Affiliation(s)
- Yun-Yi Pai
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA 15260, United States of America. Pittsburgh Quantum Institute, Pittsburgh, PA 15260, United States of America
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8
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Chung SB, Chan C, Yao H. Dislocation Majorana zero modes in perovskite oxide 2DEG. Sci Rep 2016; 6:25184. [PMID: 27139319 PMCID: PMC4853714 DOI: 10.1038/srep25184] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2015] [Accepted: 04/12/2016] [Indexed: 11/28/2022] Open
Abstract
Much of the current experimental efforts for detecting Majorana zero modes have been centered on probing the boundary of quantum wires with strong spin-orbit coupling. The same type of Majorana zero mode can also be realized at crystalline dislocations in 2D superconductors with the nontrivial weak topological indices. Unlike at an Abrikosov vortex, at such a dislocation, there is no other low-lying midgap state than the Majorana zero mode so that it avoids usual complications encountered in experimental detections such as scanning tunneling microscope (STM) measurements. We will show that, using the anisotropic dispersion of the t2g orbitals of Ti or Ta atoms, such a weak topological superconductivity can be realized when the surface two-dimensional electronic gas (2DEG) of SrTiO3 or KTaO3 becomes superconducting, which can occur through either intrinsic pairing or proximity to existing s-wave superconductors.
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Affiliation(s)
- Suk Bum Chung
- Center for Correlated Electron Systems, Institute for Basic Science (IBS), Seoul 151-742, Republic of Korea.,Department of Physics and Astronomy, Seoul National University, Seoul 151-747, Korea
| | - Cheung Chan
- Institute for Advanced Study, Tsinghua University, Beijing 100084, China
| | - Hong Yao
- Institute for Advanced Study, Tsinghua University, Beijing 100084, China
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9
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Kim G, Neumann M, Kim M, Le MD, Kang TD, Noh TW. Suppression of Three-Dimensional Charge Density Wave Ordering via Thickness Control. PHYSICAL REVIEW LETTERS 2015; 115:226402. [PMID: 26650312 DOI: 10.1103/physrevlett.115.226402] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/16/2015] [Indexed: 05/12/2023]
Abstract
Barium bismuth oxide (BaBiO_{3}) is the end member of two families of high-T_{c} superconductors, i.e., BaPb_{1-x}Bi_{x}O_{3} and Ba_{1-x}K_{x}BiO_{3}. The undoped parent compound is an insulator, exhibiting a charge density wave that is strongly linked to a static breathing distortion in the oxygen sublattice of the perovskite structure. We report a comprehensive spectroscopic and x-ray diffraction study of BaBiO_{3} thin films, showing that the minimum film thickness required to stabilize the breathing distortion and charge density wave is ≈11 unit cells, and that both phenomena are suppressed in thinner films. Our results constitute the first experimental observation of charge density wave suppression in bismuthate compounds without intentionally introducing dopants.
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Affiliation(s)
- Gideok Kim
- Center for Correlated Electron Systems, Institute for Basic Science (IBS), Seoul 151-742, Republic of Korea
- Department of Physics and Astronomy, Seoul National University, Seoul 151-742, Republic of Korea
| | - Michael Neumann
- Center for Correlated Electron Systems, Institute for Basic Science (IBS), Seoul 151-742, Republic of Korea
- Department of Physics and Astronomy, Seoul National University, Seoul 151-742, Republic of Korea
| | - Minu Kim
- Center for Correlated Electron Systems, Institute for Basic Science (IBS), Seoul 151-742, Republic of Korea
- Department of Physics and Astronomy, Seoul National University, Seoul 151-742, Republic of Korea
| | - Manh Duc Le
- Center for Correlated Electron Systems, Institute for Basic Science (IBS), Seoul 151-742, Republic of Korea
- Department of Physics and Astronomy, Seoul National University, Seoul 151-742, Republic of Korea
| | - Tae Dong Kang
- Center for Correlated Electron Systems, Institute for Basic Science (IBS), Seoul 151-742, Republic of Korea
- Department of Physics and Astronomy, Seoul National University, Seoul 151-742, Republic of Korea
| | - Tae Won Noh
- Center for Correlated Electron Systems, Institute for Basic Science (IBS), Seoul 151-742, Republic of Korea
- Department of Physics and Astronomy, Seoul National University, Seoul 151-742, Republic of Korea
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10
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Long-range electronic reconstruction to a dxz,yz-dominated Fermi surface below the LaAlO₃/SrTiO₃ interface. Sci Rep 2014; 4:5338. [PMID: 24939804 PMCID: PMC4061544 DOI: 10.1038/srep05338] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2014] [Accepted: 05/27/2014] [Indexed: 11/08/2022] Open
Abstract
Low dimensionality, broken symmetry and easily-modulated carrier concentrations provoke novel electronic phase emergence at oxide interfaces. However, the spatial extent of such reconstructions - i.e. the interfacial "depth" - remains unclear. Examining LaAlO₃/SrTiO₃ heterostructures at previously unexplored carrier densities n(2D) ≥ 6.9 × 10(14) cm(-2), we observe a Shubnikov-de Haas effect for small in-plane fields, characteristic of an anisotropic 3D Fermi surface with preferential dxz,yz orbital occupancy extending over at least 100 nm perpendicular to the interface. Quantum oscillations from the 3D Fermi surface of bulk doped SrTiO₃ emerge simultaneously at higher n(2D). We distinguish three areas in doped perovskite heterostructures: narrow (<20 nm) 2D interfaces housing superconductivity and/or other emergent phases, electronically isotropic regions far (>120 nm) from the interface and new intermediate zones where interfacial proximity renormalises the electronic structure relative to the bulk.
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11
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King PDC, McKeown Walker S, Tamai A, de la Torre A, Eknapakul T, Buaphet P, Mo SK, Meevasana W, Bahramy MS, Baumberger F. Quasiparticle dynamics and spin–orbital texture of the SrTiO3 two-dimensional electron gas. Nat Commun 2014; 5:3414. [DOI: 10.1038/ncomms4414] [Citation(s) in RCA: 126] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2013] [Accepted: 02/07/2014] [Indexed: 11/10/2022] Open
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Pentcheva R, Arras R, Otte K, Ruiz VG, Pickett WE. Termination control of electronic phases in oxide thin films and interfaces: LaAlO3/SrTiO3(001). PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2012; 370:4904-4926. [PMID: 22987035 DOI: 10.1098/rsta.2012.0202] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
A wealth of intriguing properties emerge in the seemingly simple system composed of the band insulators LaAlO(3) and SrTiO(3) such as a two-dimensional electron gas, superconductivity and magnetism. In this paper, we review the current insight obtained from first principles calculations on the mechanisms governing the behaviour of thin LaAlO(3) films on SrTiO(3)(001). In particular, we explore the strong dependence of the electronic properties on the surface and interface termination, the finite film thickness, lattice polarization and defects. A further aspect that is addressed is how the electronic behaviour and functionality can be tuned by an SrTiO(3) capping layer, adsorbates and metallic contacts. Lastly, we discuss recent reports on the coexistence of magnetism and superconductivity in this system for what they might imply about the electronic structure of this system.
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Affiliation(s)
- R Pentcheva
- Department of Earth and Environmental Sciences, Section Crystallography and Center of Nanoscience, University of Munich, Germany.
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A universal critical density underlying the physics of electrons at the LaAlO3/SrTiO3 interface. Nat Commun 2012; 3:1129. [DOI: 10.1038/ncomms2116] [Citation(s) in RCA: 253] [Impact Index Per Article: 21.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2012] [Accepted: 09/04/2012] [Indexed: 11/08/2022] Open
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King PDC, He RH, Eknapakul T, Buaphet P, Mo SK, Kaneko Y, Harashima S, Hikita Y, Bahramy MS, Bell C, Hussain Z, Tokura Y, Shen ZX, Hwang HY, Baumberger F, Meevasana W. Subband structure of a two-dimensional electron gas formed at the polar surface of the strong spin-orbit perovskite KTaO3. PHYSICAL REVIEW LETTERS 2012; 108:117602. [PMID: 22540511 DOI: 10.1103/physrevlett.108.117602] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/31/2011] [Indexed: 05/31/2023]
Abstract
We demonstrate the formation of a two-dimensional electron gas (2DEG) at the (100) surface of the 5d transition-metal oxide KTaO3. From angle-resolved photoemission, we find that quantum confinement lifts the orbital degeneracy of the bulk band structure and leads to a 2DEG composed of ladders of subband states of both light and heavy carriers. Despite the strong spin-orbit coupling, our measurements provide a direct upper bound for the potential Rashba spin splitting of only Δk(parallel)}~0.02 Å(-1) at the Fermi level. The polar nature of the KTaO3(100) surface appears to help mediate the formation of the 2DEG as compared to nonpolar SrTiO3(100).
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Affiliation(s)
- P D C King
- SUPA, School of Physics and Astronomy, University of St. Andrews, St. Andrews, Fife, United Kingdom
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Hwang HY, Iwasa Y, Kawasaki M, Keimer B, Nagaosa N, Tokura Y. Emergent phenomena at oxide interfaces. NATURE MATERIALS 2012; 11:103-13. [PMID: 22270825 DOI: 10.1038/nmat3223] [Citation(s) in RCA: 718] [Impact Index Per Article: 59.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Recent technical advances in the atomic-scale synthesis of oxide heterostructures have provided a fertile new ground for creating novel states at their interfaces. Different symmetry constraints can be used to design structures exhibiting phenomena not found in the bulk constituents. A characteristic feature is the reconstruction of the charge, spin and orbital states at interfaces on the nanometre scale. Examples such as interface superconductivity, magneto-electric coupling, and the quantum Hall effect in oxide heterostructures are representative of the scientific and technological opportunities in this rapidly emerging field.
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Affiliation(s)
- H Y Hwang
- Correlated Electron Research Group, RIKEN-Advanced Science Institute, Saitama 351-0198, Japan.
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