1
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Arnault EG, Al-Tawhid AH, Salmani-Rezaie S, Muller DA, Kumah DP, Bahramy MS, Finkelstein G, Ahadi K. Anisotropic superconductivity at KTaO 3(111) interfaces. SCIENCE ADVANCES 2023; 9:eadf1414. [PMID: 36791191 PMCID: PMC9931206 DOI: 10.1126/sciadv.adf1414] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/01/2022] [Accepted: 01/17/2023] [Indexed: 06/18/2023]
Abstract
A two-dimensional, anisotropic superconductivity was recently found at the KTaO3(111) interfaces. The nature of the anisotropic superconducting transition remains a subject of debate. To investigate the origins of the observed behavior, we grew epitaxial KTaO3(111)-based heterostructures. We show that the superconductivity is robust against the in-plane magnetic field and violates the Pauli limit. We also show that the Cooper pairs are more resilient when the bias is along [11[Formula: see text]] (I ∥ [11[Formula: see text]]) and the magnetic field is along [1[Formula: see text]0] (B ∥ [1[Formula: see text]0]). We discuss the anisotropic nature of superconductivity in the context of electronic structure, orbital character, and spin texture at the KTaO3(111) interfaces. The results point to future opportunities to enhance superconducting transition temperatures and critical fields in crystalline, two-dimensional superconductors with strong spin-orbit coupling.
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Affiliation(s)
| | - Athby H. Al-Tawhid
- Department of Materials Science and Engineering, North Carolina State University, Raleigh, NC 27265, USA
| | - Salva Salmani-Rezaie
- School of Applied and Engineering Physics, Cornell University, Ithaca, NY 14853, USA
- Kavli Institute at Cornell for Nanoscale Science, Cornell University, Ithaca, NY 14853, USA
| | - David A. Muller
- School of Applied and Engineering Physics, Cornell University, Ithaca, NY 14853, USA
- Kavli Institute at Cornell for Nanoscale Science, Cornell University, Ithaca, NY 14853, USA
| | - Divine P. Kumah
- Department of Physics, North Carolina State University, Raleigh, NC 27695, USA
| | - Mohammad S. Bahramy
- Department of Physics and Astronomy, The University of Manchester, Oxford Road, Manchester M13 9PL, UK
| | | | - Kaveh Ahadi
- Department of Materials Science and Engineering, North Carolina State University, Raleigh, NC 27265, USA
- Department of Physics, North Carolina State University, Raleigh, NC 27695, USA
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2
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Qin TX, You EM, Zhang JY, Wang HL, Zhang KHL, Mao BW, Tian ZQ. Revealing the Interaction of Charge Carrier-Phonon Coupling by Quantification of Electronic Properties at the SrTiO 3/TiO 2 Heterointerface. NANO LETTERS 2022; 22:2755-2761. [PMID: 35315673 DOI: 10.1021/acs.nanolett.1c04698] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Oxide heterointerfaces with high carrier density can interact strongly with the lattice phonons, generating considerable plasmon-phonon coupling and thereby perturbing the fascinating optical and electronic properties, such as two-dimensional electron gas, ferromagnetism, and superconductivity. Here we use infrared-spectroscopic nanoimaging based on scattering-type scanning near-field optical microscopy (s-SNOM) to quantify the interaction of electron-phonon coupling and the spatial distribution of local charge carriers at the SrTiO3/TiO2 interface. We found an increased high-frequency dielectric constant (ε∞ = 7.1-9.0) and charge carrier density (n = 6.5 × 1019 to 1.5 × 1020 cm-3) near the heterointerface. Moreover, quantitative information between the charge carrier density and extension thickness across the heterointerface has been extracted by monochromatic near-field imaging. A direct evaluation of the relationship between the thickness and the interaction of charge carrier-phonon coupling of the heterointerface would provide valuable information for the development of oxide-based electronic devices.
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Affiliation(s)
- Ting-Xiao Qin
- State Key Laboratory of Physical Chemistry of Solid Surfaces, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, People's Republic of China
- Beijing Academy of Quantum Information Sciences, Beijing 100193, People's Republic of China
| | - En-Ming You
- State Key Laboratory of Physical Chemistry of Solid Surfaces, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, People's Republic of China
| | - Jia-Ye Zhang
- State Key Laboratory of Physical Chemistry of Solid Surfaces, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, People's Republic of China
| | - Hai-Long Wang
- State Key Laboratory of Physical Chemistry of Solid Surfaces, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, People's Republic of China
- Innovation Laboratory for Sciences and Technologies of Energy Materials of Fujian Province (IKKEM), Xiamen 361101, People's Republic of China
| | - Kelvin H L Zhang
- State Key Laboratory of Physical Chemistry of Solid Surfaces, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, People's Republic of China
- Innovation Laboratory for Sciences and Technologies of Energy Materials of Fujian Province (IKKEM), Xiamen 361101, People's Republic of China
| | - Bing-Wei Mao
- State Key Laboratory of Physical Chemistry of Solid Surfaces, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, People's Republic of China
| | - Zhong-Qun Tian
- State Key Laboratory of Physical Chemistry of Solid Surfaces, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, People's Republic of China
- Innovation Laboratory for Sciences and Technologies of Energy Materials of Fujian Province (IKKEM), Xiamen 361101, People's Republic of China
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3
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Ma J, Yang R, Chen H. A large modulation of electron-phonon coupling and an emergent superconducting dome in doped strong ferroelectrics. Nat Commun 2021; 12:2314. [PMID: 33875661 PMCID: PMC8055897 DOI: 10.1038/s41467-021-22541-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2020] [Accepted: 03/17/2021] [Indexed: 11/09/2022] Open
Abstract
We use first-principles methods to study doped strong ferroelectrics (taking BaTiO3 as a prototype). Here, we find a strong coupling between itinerant electrons and soft polar phonons in doped BaTiO3, contrary to Anderson/Blount’s weakly coupled electron mechanism for "ferroelectric-like metals”. As a consequence, across a polar-to-centrosymmetric phase transition in doped BaTiO3, the total electron-phonon coupling is increased to about 0.6 around the critical concentration, which is sufficient to induce phonon-mediated superconductivity of about 2 K. Lowering the crystal symmetry of doped BaTiO3 by imposing epitaxial strain can further increase the superconducting temperature via a sizable coupling between itinerant electrons and acoustic phonons. Our work demonstrates a viable approach to modulating electron-phonon coupling and inducing phonon-mediated superconductivity in doped strong ferroelectrics and potentially in polar metals. Our results also show that the weakly coupled electron mechanism for "ferroelectric-like metals” is not necessarily present in doped strong ferroelectrics. Usually the coupling between polar phonons and itinerant electrons is weak in polar metals. Here, the authors show that in doped ferroelectrics (approximate polar metals), this coupling can be increased across the structural phase transition and as a result, phonon-mediated superconductivity emerges.
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Affiliation(s)
- Jiaji Ma
- NYU-ECNU Institute of Physics, NYU Shanghai, Shanghai, China
| | - Ruihan Yang
- NYU-ECNU Institute of Physics, NYU Shanghai, Shanghai, China
| | - Hanghui Chen
- NYU-ECNU Institute of Physics, NYU Shanghai, Shanghai, China. .,Department of Physics, New York University, New York, NY, USA.
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4
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Rose MA, Šmíd B, Vorokhta M, Slipukhina I, Andrä M, Bluhm H, Duchoň T, Ležaić M, Chambers SA, Dittmann R, Mueller DN, Gunkel F. Identifying Ionic and Electronic Charge Transfer at Oxide Heterointerfaces. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2021; 33:e2004132. [PMID: 33263190 DOI: 10.1002/adma.202004132] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/17/2020] [Revised: 08/31/2020] [Indexed: 06/12/2023]
Abstract
The ability to tailor oxide heterointerfaces has led to novel properties in low-dimensional oxide systems. A fundamental understanding of these properties is based on the concept of electronic charge transfer. However, the electronic properties of oxide heterointerfaces crucially depend on their ionic constitution and defect structure: ionic charges contribute to charge transfer and screening at oxide interfaces, triggering a thermodynamic balance of ionic and electronic structures. Quantitative understanding of the electronic and ionic roles regarding charge-transfer phenomena poses a central challenge. Here, the electronic and ionic structure is simultaneously investigated at the prototypical charge-transfer heterointerface, LaAlO3 /SrTiO3 . Applying in situ photoemission spectroscopy under oxygen ambient, ionic and electronic charge transfer is deconvoluted in response to the oxygen atmosphere at elevated temperatures. In this way, both the rich and variable chemistry of complex oxides and the associated electronic properties are equally embraced. The interfacial electron gas is depleted through an ionic rearrangement in the strontium cation sublattice when oxygen is applied, resulting in an inverse and reversible balance between cation vacancies and electrons, while the mobility of ionic species is found to be considerably enhanced as compared to the bulk. Triggered by these ionic phenomena, the electronic transport and magnetic signature of the heterointerface are significantly altered.
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Affiliation(s)
- Marc-André Rose
- Institute for Electronic Materials (IWE 2), and Juelich-Aachen Research Alliance for Fundamentals on Future Information Technology (JARA-FIT), RWTH Aachen University, 52074, Aachen, Germany
- Peter Grünberg Institute 7, Forschungszentrum Jülich GmbH, and JARA-FIT, 52425, Jülich, Germany
| | - Břetislav Šmíd
- Department of Surface and Plasma Science, Faculty of Mathematics and Physics, Charles University, Prague, 180 00, Czech Republic
| | - Mykhailo Vorokhta
- Department of Surface and Plasma Science, Faculty of Mathematics and Physics, Charles University, Prague, 180 00, Czech Republic
| | - Ivetta Slipukhina
- Peter Grünberg Institute 1 and Institute for Advanced Simulation, Forschungszentrum Jülich GmbH and JARA-FIT, 52425, Jülich, Germany
| | - Michael Andrä
- Peter Grünberg Institute 7, Forschungszentrum Jülich GmbH, and JARA-FIT, 52425, Jülich, Germany
| | - Hendrik Bluhm
- Chemical Sciences Division, Lawrence Berkeley National Lab., Berkeley, CA, 94720, USA
- Department of Inorganic Chemistry, Fritz Haber Institute of the Max Planck Society, 14195, Berlin, Germany
| | - Tomáš Duchoň
- Peter Grünberg Institute 6, and JARA-FIT, Forschungszentrum Jülich GmbH, 52425, Jülich, Germany
| | - Marjana Ležaić
- Peter Grünberg Institute 1 and Institute for Advanced Simulation, Forschungszentrum Jülich GmbH and JARA-FIT, 52425, Jülich, Germany
| | - Scott A Chambers
- Physical and Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland, WA, 99354, USA
| | - Regina Dittmann
- Peter Grünberg Institute 7, Forschungszentrum Jülich GmbH, and JARA-FIT, 52425, Jülich, Germany
| | - David N Mueller
- Peter Grünberg Institute 7, Forschungszentrum Jülich GmbH, and JARA-FIT, 52425, Jülich, Germany
- Peter Grünberg Institute 6, and JARA-FIT, Forschungszentrum Jülich GmbH, 52425, Jülich, Germany
| | - Felix Gunkel
- Institute for Electronic Materials (IWE 2), and Juelich-Aachen Research Alliance for Fundamentals on Future Information Technology (JARA-FIT), RWTH Aachen University, 52074, Aachen, Germany
- Peter Grünberg Institute 7, Forschungszentrum Jülich GmbH, and JARA-FIT, 52425, Jülich, Germany
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5
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Zwiebler M, Di Gennaro E, Hamann-Borrero JE, Ritschel T, Green RJ, Sawatzky GA, Schierle E, Weschke E, Leo A, Granozio FM, Geck J. Transition from a uni- to a bimodal interfacial charge distribution in [Formula: see text]/[Formula: see text] upon cooling. Sci Rep 2020; 10:18359. [PMID: 33110119 PMCID: PMC7591581 DOI: 10.1038/s41598-020-74364-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2020] [Accepted: 09/17/2020] [Indexed: 11/09/2022] Open
Abstract
We present a combined resonant soft X-ray reflectivity and electric transport study of [Formula: see text]/[Formula: see text] field effect devices. The depth profiles with atomic layer resolution that are obtained from the resonant reflectivity reveal a pronounced temperature dependence of the two-dimensional electron liquid at the [Formula: see text]/[Formula: see text] interface. At room temperature the corresponding electrons are located close to the interface, extending down to 4 unit cells into the [Formula: see text] substrate. Upon cooling, however, these interface electrons assume a bimodal depth distribution: They spread out deeper into the [Formula: see text] and split into two distinct parts, namely one close to the interface with a thickness of about 4 unit cells and another centered around 9 unit cells from the interface. The results are consistent with theoretical predictions based on oxygen vacancies at the surface of the [Formula: see text] film and support the notion of a complex interplay between structural and electronic degrees of freedom.
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Affiliation(s)
- M. Zwiebler
- Institut für Festkörper- und Materialphysik, Technische Universität Dresden, 01062 Dresden, Germany
| | - E. Di Gennaro
- Dipartimento di Fisica “E. Pancini”, Università di Napoli “Federico II”, Complesso Universitario di Monte S. Angelo, Via Cintia, 80126 Naples, Italy
- CNR-SPIN, Complesso Universitario di Monte S. Angelo, Via Cintia, 80126 Naples, Italy
| | - J. E. Hamann-Borrero
- Institut für Festkörper- und Materialphysik, Technische Universität Dresden, 01062 Dresden, Germany
| | - T. Ritschel
- Institut für Festkörper- und Materialphysik, Technische Universität Dresden, 01062 Dresden, Germany
| | - R. J. Green
- Stewart Blusson Quantum Matter Institute, University of British Columbia, Vancouver, V6T 1Z1 Canada
- Department of Physics and Engineering Physics, University of Saskatchewan, Saskatoon, S7N 5E2 Canada
| | - G. A. Sawatzky
- Stewart Blusson Quantum Matter Institute, University of British Columbia, Vancouver, V6T 1Z1 Canada
| | - E. Schierle
- Helmholtz-Zentrum Berlin, BESSY, Albert-Einstein-Str. 15, 12489 Berlin, Germany
| | - E. Weschke
- Helmholtz-Zentrum Berlin, BESSY, Albert-Einstein-Str. 15, 12489 Berlin, Germany
| | - A. Leo
- Dipartimento di Fisica “E. R. Caianiello”, Università degli Studi di Salerno, Fisciano, Italy
- CNR-SPIN, Campus di Fisciano-Salerno, Fisciano, Italy
| | - F. Miletto Granozio
- CNR-SPIN, Complesso Universitario di Monte S. Angelo, Via Cintia, 80126 Naples, Italy
| | - J. Geck
- Institut für Festkörper- und Materialphysik, Technische Universität Dresden, 01062 Dresden, Germany
- Würzburg-Dresden Cluster of Excellence ct.qmat, Technische Universität Dresden, 01062 Dresden, Germany
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6
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Chapman KS, Atkinson WA. Modified transverse Ising model for the dielectric properties of SrTiO 3 films and interfaces. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2020; 32:065303. [PMID: 31634883 DOI: 10.1088/1361-648x/ab4fa7] [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 transverse Ising model (TIM), with pseudospins representing the lattice polarization, is often used as a simple description of ferroelectric materials. However, we demonstrate that the TIM, as it is usually formulated, provides an incorrect description of SrTiO3 films and interfaces because of its inadequate treatment of spatial inhomogeneity. We correct this deficiency by adding a pseudospin anisotropy to the model. We demonstrate the physical need for this term by comparison of the TIM to a typical Landau-Ginzburg-Devonshire model. We then demonstrate the physical consequences of the modification for two model systems: a ferroelectric thin film, and a metallic LaAlO3/SrTiO3 interface. We show that, in both cases, the modified TIM has a substantially different polarization profile than the conventional TIM. In particular, at low temperatures the formation of quantized states at LaAlO3/SrTiO3 interfaces only occurs in the modified TIM.
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Affiliation(s)
- Kelsey S Chapman
- Department of Physics and Astronomy, Trent University, Peterborough, Ontario, K9L 0G2, Canada
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7
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Lim ZH, Quackenbush NF, Penn AN, Chrysler M, Bowden M, Zhu Z, Ablett JM, Lee TL, LeBeau JM, Woicik JC, Sushko PV, Chambers SA, Ngai JH. Charge Transfer and Built-in Electric Fields between a Crystalline Oxide and Silicon. PHYSICAL REVIEW LETTERS 2019; 123:026805. [PMID: 31386492 DOI: 10.1103/physrevlett.123.026805] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/18/2018] [Revised: 01/16/2019] [Indexed: 06/10/2023]
Abstract
We report charge transfer and built-in electric fields across the epitaxial SrNb_{x}Ti_{1-x}O_{3-δ}/Si(001) interface. Electrical transport measurements indicate the formation of a hole gas in the Si and the presence of built-in fields. Hard x-ray photoelectron measurements reveal pronounced asymmetries in core-level spectra that arise from these built-in fields. Theoretical analysis of core-level spectra enables built-in fields and the resulting band bending to be spatially mapped across the heterojunction. The demonstration of tunable charge transfer, built-in fields, and the spatial mapping of the latter, lays the groundwork for the development of electrically coupled, functional heterojunctions.
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Affiliation(s)
- Z H Lim
- Department of Physics, University of Texas-Arlington, Arlington, Texas 76019, USA
| | - N F Quackenbush
- Material Measurement Laboratory, Materials Measurement Science Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA
| | - A N Penn
- Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695, USA
| | - M Chrysler
- Department of Physics, University of Texas-Arlington, Arlington, Texas 76019, USA
| | - M Bowden
- Environmental Molecular Sciences Laboratory Pacific Northwest National Laboratory, Richland, Washington 99352, USA
| | - Z Zhu
- Environmental Molecular Sciences Laboratory Pacific Northwest National Laboratory, Richland, Washington 99352, USA
| | - J M Ablett
- Synchrotron SOLEIL, L'Orme des Merisiers, Saint-Aubin, BP 48, 91192 Gif-sur-Yvette, France
| | - T-L Lee
- Diamond Light Source, Ltd., Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0DE, United Kingdom
| | - J M LeBeau
- Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695, USA
| | - J C Woicik
- Material Measurement Laboratory, Materials Measurement Science Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA
| | - P V Sushko
- Physical and Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland, Washington 99352, USA
| | - S A Chambers
- Physical and Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland, Washington 99352, USA
| | - J H Ngai
- Department of Physics, University of Texas-Arlington, Arlington, Texas 76019, USA
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8
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Zhang F, Lv P, Zhang Y, Huang S, Wong CM, Yau HM, Chen X, Wen Z, Jiang X, Zeng C, Hong J, Dai JY. Modulating the Electrical Transport in the Two-Dimensional Electron Gas at LaAlO_{3}/SrTiO_{3} Heterostructures by Interfacial Flexoelectricity. PHYSICAL REVIEW LETTERS 2019; 122:257601. [PMID: 31347866 DOI: 10.1103/physrevlett.122.257601] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/29/2018] [Revised: 04/12/2019] [Indexed: 06/10/2023]
Abstract
Thin film flexoelectricity is attracting more attention because of its enhanced effect and potential application in electronic devices. Here we find that a mechanical bending induced flexoelectricity significantly modulates the electrical transport properties of the interfacial two-dimensional electron gas (2DEG) at the LaAlO_{3}/SrTiO_{3} (LAO/STO) heterostructure. Under variant bending states, both the carrier density and mobility of the 2DEG are changed according to the flexoelectric polarization direction, showing an electric field effect modulation. By measuring the flexoelectric response of LAO, it is found that the effective flexoelectricity in the LAO thin film is enhanced by 3 orders compared to its bulk. These results broaden the horizon of study on the flexoelectricity effect in the hetero-oxide interface and more research on the oxide interfacial flexoelectricity may be stimulated.
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Affiliation(s)
- Fan Zhang
- Department of Applied Physics, The Hong Kong Polytechnic University, Hung Hom, 999077 Kowloon, Hong Kong
- Department of Mechanical and Aerospace Engineering, North Carolina State University, Raleigh, North Carolina, 27606, USA
| | - Peng Lv
- School of Aerospace Engineering, Beijing Institute of Technology, Beijing, 100081, People's Republic of China
| | - Yiteng Zhang
- College of Physics, Qingdao University, Qingdao, 266071, China
| | - Shujin Huang
- Department of Mechanical and Aerospace Engineering, North Carolina State University, Raleigh, North Carolina, 27606, USA
| | - Chi-Man Wong
- Department of Applied Physics, The Hong Kong Polytechnic University, Hung Hom, 999077 Kowloon, Hong Kong
| | - Hei-Man Yau
- Department of Applied Physics, The Hong Kong Polytechnic University, Hung Hom, 999077 Kowloon, Hong Kong
| | - Xinxin Chen
- Department of Applied Physics, The Hong Kong Polytechnic University, Hung Hom, 999077 Kowloon, Hong Kong
| | - Zheng Wen
- College of Physics, Qingdao University, Qingdao, 266071, China
| | - Xiaoning Jiang
- Department of Mechanical and Aerospace Engineering, North Carolina State University, Raleigh, North Carolina, 27606, USA
| | - Changgan Zeng
- International Center for Quantum Design of Functional Materials, Hefei National Laboratory for Physical Sciences at the Microscale, CAS Key Laboratory of Strongly Coupled Quantum Matter Physics, and Department of Physics, University of Science and Technology of China, Hefei, 230026, China
| | - Jiawang Hong
- School of Aerospace Engineering, Beijing Institute of Technology, Beijing, 100081, People's Republic of China
| | - Ji-Yan Dai
- Department of Applied Physics, The Hong Kong Polytechnic University, Hung Hom, 999077 Kowloon, Hong Kong
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9
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Manca N, Bothner D, Monteiro AMRVL, Davidovikj D, Sağlam YG, Jenkins M, Gabay M, Steele GA, Caviglia AD. Bimodal Phase Diagram of the Superfluid Density in LaAlO_{3}/SrTiO_{3} Revealed by an Interfacial Waveguide Resonator. PHYSICAL REVIEW LETTERS 2019; 122:036801. [PMID: 30735404 DOI: 10.1103/physrevlett.122.036801] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/01/2018] [Indexed: 06/09/2023]
Abstract
We explore the superconducting phase diagram of the two-dimensional electron system at the LaAlO_{3}/SrTiO_{3} interface by monitoring the frequencies of the cavity modes of a coplanar waveguide resonator fabricated in the interface itself. We determine the phase diagram of the superconducting transition as a function of the temperature and electrostatic gating, finding that both the superfluid density and the transition temperature follow a dome shape but that the two are not monotonically related. The ground state of this two-dimensional electron system is interpreted as a Josephson junction array, where a transition from long- to short-range order occurs as a function of the electronic doping. The synergy between correlated oxides and superconducting circuits is revealed to be a promising route to investigate these exotic compounds, complementary to standard magnetotransport measurements.
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Affiliation(s)
- Nicola Manca
- Kavli Institute of Nanoscience, Delft University of Technology, P.O. Box 5046, 2600 GA Delft, Netherlands
| | - Daniel Bothner
- Kavli Institute of Nanoscience, Delft University of Technology, P.O. Box 5046, 2600 GA Delft, Netherlands
| | - Ana M R V L Monteiro
- Kavli Institute of Nanoscience, Delft University of Technology, P.O. Box 5046, 2600 GA Delft, Netherlands
| | - Dejan Davidovikj
- Kavli Institute of Nanoscience, Delft University of Technology, P.O. Box 5046, 2600 GA Delft, Netherlands
| | - Yildiz G Sağlam
- Kavli Institute of Nanoscience, Delft University of Technology, P.O. Box 5046, 2600 GA Delft, Netherlands
| | - Mark Jenkins
- Kavli Institute of Nanoscience, Delft University of Technology, P.O. Box 5046, 2600 GA Delft, Netherlands
| | - Marc Gabay
- Laboratoire de Physique des Solides, Universite Paris-Sud and CNRS, Batiment 510, 91450 Orsay, France
| | - Gary A Steele
- Kavli Institute of Nanoscience, Delft University of Technology, P.O. Box 5046, 2600 GA Delft, Netherlands
| | - Andrea D Caviglia
- Kavli Institute of Nanoscience, Delft University of Technology, P.O. Box 5046, 2600 GA Delft, Netherlands
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10
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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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11
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Li C, Jiang W, Liu M, Hong Y, Xue H, Meng J, Zhang Z, Li Y, Liu K, He L, Dou R, Xiong C, Nie J. Interaction between in-gap states and carriers at the conductive interface between perovskite oxides. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2018; 30:405002. [PMID: 30152788 DOI: 10.1088/1361-648x/aadd33] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
The 2D electron systems of SrTiO3/NdGaO3 (STO/NGO) and amorphous-LaAlO3/SrTiO3/NdGaO3 (a-LAO/STO/NGO) heterojunctions were explored. An obvious interaction between in-gap states (IGSs) and carriers was found. The IGSs can trap a large number of carriers and enhance carrier scattering. As a result of the high density of IGSs in STO, the conductivity of STO/NGO was severely weakened. However, for a-LAO/STO/NGO heterojunctions, the high carrier density can reduce the effect of IGSs through the electrostatic screening effect. The competition between IGSs and the screening effect of carriers results in an insulator-metal transition and a strange temperature dependence of carrier density. We also explored the interaction between IGSs and carriers theoretically. A mathematical description was proposed and the calculated results showed good agreement with experimental findings.
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Affiliation(s)
- Chengjian Li
- Department of Physics, Beijing Normal University, Beijing 100875, People's Republic of China
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12
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Zhang H, Yun Y, Zhang X, Zhang H, Ma Y, Yan X, Wang F, Li G, Li R, Khan T, Chen Y, Liu W, Hu F, Liu B, Shen B, Han W, Sun J. High-Mobility Spin-Polarized Two-Dimensional Electron Gases at EuO/KTaO_{3} Interfaces. PHYSICAL REVIEW LETTERS 2018; 121:116803. [PMID: 30265094 DOI: 10.1103/physrevlett.121.116803] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/07/2018] [Revised: 05/16/2018] [Indexed: 06/08/2023]
Abstract
Two-dimensional electron gases (2DEGs) at oxide interfaces, which provide unique playgrounds for emergent phenomena, have attracted increasing attention in recent years. While most of the previous works focused on the 2DEGs at LaAlO_{3}/SrTiO_{3} interfaces, here we report on a new kind of 2DEGs formed between a magnetic insulator EuO and a high-k perovskite KTaO_{3}. The 2DEGs are not only highly conducting, with a maximal Hall mobility of 111.6 cm^{2}/V s at 2 K, but also well spin polarized, showing strongly hysteretic magnetoresistance up to 25 K and well-defined anomalous Hall effect up to 70 K. Moreover, unambiguous correspondences between the hysteretic behaviors of 2DEGs and the EuO layer are captured, suggesting the proximity effect of the latter on the former. This is confirmed by the results of density-functional theory calculations: Through interlayer exchange, EuO drives the neighboring TaO_{2} layer into a ferromagnetic state. The present work opens new avenues for the exploration for high performance spin-polarized 2DEGs at oxide interfaces.
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Affiliation(s)
- Hongrui Zhang
- Beijing National Laboratory for Condensed Matter & Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
- University of Chinese Academy of Sciences, Beijing 100049, People's Republic of China
| | - Yu Yun
- International Centre for Quantum Materials, School of Physics, Peking University, Beijing 100871, People's Republic of China
- Collaborative Innovation Centre of Quantum Matter, Beijing 100871, People's Republic of China
| | - Xuejing Zhang
- Beijing National Laboratory for Condensed Matter & Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
- University of Chinese Academy of Sciences, Beijing 100049, People's Republic of China
| | - Hui Zhang
- Beijing National Laboratory for Condensed Matter & Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
- University of Chinese Academy of Sciences, Beijing 100049, People's Republic of China
| | - Yang Ma
- International Centre for Quantum Materials, School of Physics, Peking University, Beijing 100871, People's Republic of China
- Collaborative Innovation Centre of Quantum Matter, Beijing 100871, People's Republic of China
| | - Xi Yan
- Beijing National Laboratory for Condensed Matter & Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
- University of Chinese Academy of Sciences, Beijing 100049, People's Republic of China
| | - Fei Wang
- University of Chinese Academy of Sciences, Beijing 100049, People's Republic of China
- Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang 110016, People's Republic of China
| | - Gang Li
- Beijing National Laboratory for Condensed Matter & Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
- University of Chinese Academy of Sciences, Beijing 100049, People's Republic of China
| | - Rui Li
- Beijing National Laboratory for Condensed Matter & Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
- University of Chinese Academy of Sciences, Beijing 100049, People's Republic of China
| | - Tahira Khan
- Beijing National Laboratory for Condensed Matter & Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
- University of Chinese Academy of Sciences, Beijing 100049, People's Republic of China
| | - Yuansha Chen
- Beijing National Laboratory for Condensed Matter & Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
- University of Chinese Academy of Sciences, Beijing 100049, People's Republic of China
| | - Wei Liu
- University of Chinese Academy of Sciences, Beijing 100049, People's Republic of China
- Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang 110016, People's Republic of China
| | - Fengxia Hu
- Beijing National Laboratory for Condensed Matter & Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
- University of Chinese Academy of Sciences, Beijing 100049, People's Republic of China
| | - Banggui Liu
- Beijing National Laboratory for Condensed Matter & Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
- University of Chinese Academy of Sciences, Beijing 100049, People's Republic of China
| | - Baogen Shen
- Beijing National Laboratory for Condensed Matter & Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
- University of Chinese Academy of Sciences, Beijing 100049, People's Republic of China
| | - Wei Han
- International Centre for Quantum Materials, School of Physics, Peking University, Beijing 100871, People's Republic of China
- Collaborative Innovation Centre of Quantum Matter, Beijing 100871, People's Republic of China
| | - Jirong Sun
- Beijing National Laboratory for Condensed Matter & Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
- University of Chinese Academy of Sciences, Beijing 100049, People's Republic of China
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13
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Li D, Lemal S, Gariglio S, Wu Z, Fête A, Boselli M, Ghosez P, Triscone J. Probing Quantum Confinement and Electronic Structure at Polar Oxide Interfaces. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2018; 5:1800242. [PMID: 30128239 PMCID: PMC6097152 DOI: 10.1002/advs.201800242] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/12/2018] [Revised: 04/28/2018] [Indexed: 06/08/2023]
Abstract
Polar discontinuities occurring at interfaces between two materials constitute both a challenge and an opportunity in the study and application of a variety of devices. In order to cure the large electric field occurring in such structures, a reconfiguration of the charge landscape sets in at the interface via chemical modifications, adsorbates, or charge transfer. In the latter case, one may expect a local electronic doping of one material: one example is the two-dimensional electron liquid (2DEL) appearing in SrTiO3 once covered by a polar LaAlO3 layer. Here, it is shown that tuning the formal polarization of a (La,Al)1-x (Sr,Ti) x O3 (LASTO:x) overlayer modifies the quantum confinement of the 2DEL in SrTiO3 and its electronic band structure. The analysis of the behavior in magnetic field of superconducting field-effect devices reveals, in agreement with ab initio calculations and self-consistent Poisson-Schrödinger modeling, that quantum confinement and energy splitting between electronic bands of different symmetries strongly depend on the interface total charge densities. These results strongly support the polar discontinuity mechanisms with a full charge transfer to explain the origin of the 2DEL at the celebrated LaAlO3/SrTiO3 interface and demonstrate an effective tool for tailoring the electronic structure at oxide interfaces.
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Affiliation(s)
- Danfeng Li
- Department of Quantum Matter PhysicsUniversity of Geneva24 quai Ernest‐AnsermetCH‐1211Geneva 4Switzerland
| | - Sébastien Lemal
- Theoretical Materials PhysicsQ‐MATCESAMUniversité de LiègeB‐4000LiègeBelgium
| | - Stefano Gariglio
- Department of Quantum Matter PhysicsUniversity of Geneva24 quai Ernest‐AnsermetCH‐1211Geneva 4Switzerland
| | - Zhenping Wu
- Department of Quantum Matter PhysicsUniversity of Geneva24 quai Ernest‐AnsermetCH‐1211Geneva 4Switzerland
- State Key Laboratory of Information Photonics and Optical Communications and School of ScienceBeijing University of Posts and TelecommunicationsBeijing100876China
| | - Alexandre Fête
- Department of Quantum Matter PhysicsUniversity of Geneva24 quai Ernest‐AnsermetCH‐1211Geneva 4Switzerland
| | - Margherita Boselli
- Department of Quantum Matter PhysicsUniversity of Geneva24 quai Ernest‐AnsermetCH‐1211Geneva 4Switzerland
| | - Philippe Ghosez
- Theoretical Materials PhysicsQ‐MATCESAMUniversité de LiègeB‐4000LiègeBelgium
| | - Jean‐Marc Triscone
- Department of Quantum Matter PhysicsUniversity of Geneva24 quai Ernest‐AnsermetCH‐1211Geneva 4Switzerland
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14
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He P, Walker SM, Zhang SSL, Bruno FY, Bahramy MS, Lee JM, Ramaswamy R, Cai K, Heinonen O, Vignale G, Baumberger F, Yang H. Observation of Out-of-Plane Spin Texture in a SrTiO_{3}(111) Two-Dimensional Electron Gas. PHYSICAL REVIEW LETTERS 2018; 120:266802. [PMID: 30004757 DOI: 10.1103/physrevlett.120.266802] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/21/2018] [Indexed: 06/08/2023]
Abstract
We explore the second order bilinear magnetoelectric resistance (BMER) effect in the d-electron-based two-dimensional electron gas (2DEG) at the SrTiO_{3}(111) surface. We find evidence of a spin-split band structure with the archetypal spin-momentum locking of the Rashba effect for the in-plane component. Under an out-of-plane magnetic field, we find a BMER signal that breaks the sixfold symmetry of the electronic dispersion, which is a fingerprint for the presence of a momentum-dependent out-of-plane spin component. Relativistic electronic structure calculations reproduce this spin texture and indicate that the out-of-plane component is a ubiquitous property of oxide 2DEGs arising from strong crystal field effects. We further show that the BMER response of the SrTiO_{3}(111) 2DEG is tunable and unexpectedly large.
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Affiliation(s)
- Pan He
- Department of Electrical and Computer Engineering, and NUSNNI, National University of Singapore, 117576 Singapore, Singapore
| | - S McKeown Walker
- Department of Quantum Matter Physics, University of Geneva, 24 Quai Ernest-Ansermet, 1211 Genève 4, Switzerland
| | - Steven S-L Zhang
- Materials Science Division, Argonne National Laboratory, Lemont, Illinois 60439, USA
| | - F Y Bruno
- Department of Quantum Matter Physics, University of Geneva, 24 Quai Ernest-Ansermet, 1211 Genève 4, Switzerland
| | - M S Bahramy
- Quantum-Phase Electronics Center, Department of Applied Physics, The University of Tokyo, Tokyo 113-8656, Japan
- RIKEN Center for Emergent Matter Science (CEMS), Wako 351-0198, Japan
| | - Jong Min Lee
- Department of Electrical and Computer Engineering, and NUSNNI, National University of Singapore, 117576 Singapore, Singapore
| | - Rajagopalan Ramaswamy
- Department of Electrical and Computer Engineering, and NUSNNI, National University of Singapore, 117576 Singapore, Singapore
| | - Kaiming Cai
- Department of Electrical and Computer Engineering, and NUSNNI, National University of Singapore, 117576 Singapore, Singapore
| | - Olle Heinonen
- Materials Science Division, Argonne National Laboratory, Lemont, Illinois 60439, USA
| | - Giovanni Vignale
- Department of Physics and Astronomy, University of Missouri, Columbia, Missouri 65211, USA
| | - F Baumberger
- Department of Quantum Matter Physics, University of Geneva, 24 Quai Ernest-Ansermet, 1211 Genève 4, Switzerland
- Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
| | - Hyunsoo Yang
- Department of Electrical and Computer Engineering, and NUSNNI, National University of Singapore, 117576 Singapore, Singapore
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15
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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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16
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Electrons and Polarons at Oxide Interfaces Explored by Soft-X-Ray ARPES. SPECTROSCOPY OF COMPLEX OXIDE INTERFACES 2018. [DOI: 10.1007/978-3-319-74989-1_6] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
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17
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Dielectric collapse at the LaAlO 3/SrTiO 3 (001) heterointerface under applied electric field. Sci Rep 2017; 7:9516. [PMID: 28842643 PMCID: PMC5573322 DOI: 10.1038/s41598-017-09920-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2017] [Accepted: 08/01/2017] [Indexed: 11/25/2022] Open
Abstract
The fascinating interfacial transport properties at the LaAlO3/SrTiO3 heterointerface have led to intense investigations of this oxide system. Exploiting the large dielectric constant of SrTiO3 at low temperatures, tunability in the interfacial conductivity over a wide range has been demonstrated using a back-gate device geometry. In order to understand the effect of back-gating, it is crucial to assess the interface band structure and its evolution with external bias. In this study, we report measurements of the gate-bias dependent interface band alignment, especially the confining potential profile, at the conducting LaAlO3/SrTiO3 (001) heterointerface using soft and hard x-ray photoemission spectroscopy in conjunction with detailed model simulations. Depth-profiling analysis incorporating the electric field dependent dielectric constant in SrTiO3 reveals that a significant potential drop on the SrTiO3 side of the interface occurs within ~2 nm of the interface under negative gate-bias. These results demonstrate gate control of the collapse of the dielectric permittivity at the interface, and explain the dramatic loss of electron mobility with back-gate depletion.
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18
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Vaz DC, Lesne E, Sander A, Naganuma H, Jacquet E, Santamaria J, Barthélémy A, Bibes M. Tuning Up or Down the Critical Thickness in LaAlO 3 /SrTiO 3 through In Situ Deposition of Metal Overlayers. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2017; 29:1700486. [PMID: 28505388 DOI: 10.1002/adma.201700486] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/24/2017] [Revised: 03/28/2017] [Indexed: 06/07/2023]
Abstract
The quasi 2D electron system (q2DES) that forms at the interface between LaAlO3 and SrTiO3 has attracted much attention from the oxide electronics community. One of its hallmark features is the existence of a critical LaAlO3 thickness of 4 unit-cells (uc) for interfacial conductivity to emerge. In this paper, the chemical, electronic, and transport properties of LaAlO3 /SrTiO3 samples capped with different metals grown in a system combining pulsed laser deposition, sputtering, and in situ X-ray photoemission spectroscopy are investigated. The results show that for metals with low work function a q2DES forms at 1-2 uc of LaAlO3 and is accompanied by a partial oxidation of the metal, a phenomenon that affects the q2DES properties and triggers the formation of defects. In contrast, for noble metals, the critical thickness is increased above 4 uc. The results are discussed in terms of a hybrid mechanism that incorporates electrostatic and chemical effects.
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Affiliation(s)
- Diogo Castro Vaz
- Unité Mixte de Physique UMR 137 CNRS/Thales, Université Paris-Sud, Université Paris-Saclay, 91767, Palaiseau, France
| | - Edouard Lesne
- Unité Mixte de Physique UMR 137 CNRS/Thales, Université Paris-Sud, Université Paris-Saclay, 91767, Palaiseau, France
| | - Anke Sander
- Unité Mixte de Physique UMR 137 CNRS/Thales, Université Paris-Sud, Université Paris-Saclay, 91767, Palaiseau, France
| | - Hiroshi Naganuma
- Unité Mixte de Physique UMR 137 CNRS/Thales, Université Paris-Sud, Université Paris-Saclay, 91767, Palaiseau, France
- Department of Applied Physics, Graduate School of Engineering, Tohoku University, Sendai, 980-8579, Japan
| | - Eric Jacquet
- Unité Mixte de Physique UMR 137 CNRS/Thales, Université Paris-Sud, Université Paris-Saclay, 91767, Palaiseau, France
| | - Jacobo Santamaria
- Unité Mixte de Physique UMR 137 CNRS/Thales, Université Paris-Sud, Université Paris-Saclay, 91767, Palaiseau, France
- Instituto de Magnetismo Aplicado, Universidad Complutense de Madrid, 28040, Madrid, Spain
| | - Agnès Barthélémy
- Unité Mixte de Physique UMR 137 CNRS/Thales, Université Paris-Sud, Université Paris-Saclay, 91767, Palaiseau, France
| | - Manuel Bibes
- Unité Mixte de Physique UMR 137 CNRS/Thales, Université Paris-Sud, Université Paris-Saclay, 91767, Palaiseau, France
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19
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Ohshima R, Ando Y, Matsuzaki K, Susaki T, Weiler M, Klingler S, Huebl H, Shikoh E, Shinjo T, Goennenwein STB, Shiraishi M. Strong evidence for d-electron spin transport at room temperature at a LaAlO 3/SrTiO 3 interface. NATURE MATERIALS 2017; 16:609-614. [PMID: 28191896 DOI: 10.1038/nmat4857] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/04/2016] [Accepted: 01/16/2017] [Indexed: 06/06/2023]
Abstract
A d-orbital electron has an anisotropic electron orbital and is a source of magnetism. The realization of a two-dimensional electron gas (2DEG) embedded at a LaAlO3/SrTiO3 interface surprised researchers in materials and physical sciences because the 2DEG consists of 3d-electrons of Ti with extraordinarily large carrier mobility, even in the insulating oxide heterostructure. To date, a wide variety of physical phenomena, such as ferromagnetism and the quantum Hall effect, have been discovered in this 2DEG system, demonstrating the ability of d-electron 2DEG systems to provide a material platform for the study of interesting physics. However, because of both ferromagnetism and the Rashba field, long-range spin transport and the exploitation of spintronics functions have been believed difficult to implement in d-electron 2DEG systems. Here, we report the experimental demonstration of room-temperature spin transport in a d-electron-based 2DEG at a LaAlO3/SrTiO3 interface, where the spin relaxation length is about 300 nm. Our finding, which counters the conventional understandings of d-electron 2DEGs, highlights the spin-functionality of conductive oxide systems and opens the field of d-electron spintronics.
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Affiliation(s)
- Ryo Ohshima
- Department of Electronic Science and Engineering, Kyoto University, 615-8510 Kyoto, Japan
- Graduate School of Engineering Science, Osaka University, 560-8531 Toyonaka, Japan
| | - Yuichiro Ando
- Department of Electronic Science and Engineering, Kyoto University, 615-8510 Kyoto, Japan
| | - Kosuke Matsuzaki
- Secure Materials Center, Materials and Structures Laboratories, Tokyo Institute of Technology, 226-8503 Yokohama, Japan
| | - Tomofumi Susaki
- Secure Materials Center, Materials and Structures Laboratories, Tokyo Institute of Technology, 226-8503 Yokohama, Japan
| | - Mathias Weiler
- Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, 85748 Garching, Germany
- Physik-Department, Technische Universität München, 85748 Garching, Germany
| | - Stefan Klingler
- Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, 85748 Garching, Germany
- Physik-Department, Technische Universität München, 85748 Garching, Germany
| | - Hans Huebl
- Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, 85748 Garching, Germany
- Physik-Department, Technische Universität München, 85748 Garching, Germany
- Nanosystems Initiative Munich, 80799 München, Germany
| | - Eiji Shikoh
- Graduate School of Engineering, Osaka City University, 558-8585 Osaka, Japan
| | - Teruya Shinjo
- Department of Electronic Science and Engineering, Kyoto University, 615-8510 Kyoto, Japan
| | - Sebastian T B Goennenwein
- Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, 85748 Garching, Germany
- Physik-Department, Technische Universität München, 85748 Garching, Germany
- Nanosystems Initiative Munich, 80799 München, Germany
| | - Masashi Shiraishi
- Department of Electronic Science and Engineering, Kyoto University, 615-8510 Kyoto, Japan
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20
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Gunkel F, Heinen RA, Hoffmann-Eifert S, Jin L, Jia CL, Dittmann R. Mobility Modulation and Suppression of Defect Formation in Two-Dimensional Electron Systems by Charge-Transfer Management. ACS APPLIED MATERIALS & INTERFACES 2017; 9:10888-10896. [PMID: 28262026 DOI: 10.1021/acsami.7b00905] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Electron mobility is one of the most-debated key attributes of low-dimensional electron systems emerging at complex oxide heterointerfaces. However, a common understanding of how electron mobility can be optimized in these systems has not been achieved so far. Here, we discuss a novel approach for achieving a systematic increase in electron mobility in polar/nonpolar perovskite interfaces by suppressing the thermodynamically required defect formation at the nanoscale. We discuss the transport properties of electron gases established at interfaces between SrTiO3 and various polar perovskites [LaAlO3, NdGaO3, and (La,Sr)(Al,Ta)O3], allowing for the individual variation of epitaxial strain and charge transfer among these epitaxial interfaces. As we show, the reduced charge transfer at (La,Sr)(Al,Ta)O3/SrTiO3 interfaces yields a systematic increase in electron mobility, while the reduced epitaxial strain has only minor impact. As thermodynamic continuum simulations suggest, the charge transfer across these interfaces affects both the spatial distribution of electrons and the background distribution of ionic defects, acting as major scatter centers within the potential well. Easing charge transfer in (La,Sr)(Al,Ta)O3/SrTiO3 yields an enlarged spatial separation of mobile charge carriers and scattering centers, as well as a reduced driving force for the formation of ionic defects at the nanoscale. Our results suggest a general recipe for achieving electron enhancements at oxide heterostructure interfaces and provide new perspectives for atomistic understanding of electron scattering in these systems.
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Affiliation(s)
- Felix Gunkel
- Institute of Electronic Materials, RWTH Aachen University , 52062 Aachen, Germany
- Peter Grünberg Institute, Fundamentals of Future Information Technology, Jülich Aachen Research Alliance, Forschungszentrum Jülich , 52425 Jülich, Germany
| | - Ronja A Heinen
- Peter Grünberg Institute, Fundamentals of Future Information Technology, Jülich Aachen Research Alliance, Forschungszentrum Jülich , 52425 Jülich, Germany
| | - Susanne Hoffmann-Eifert
- Peter Grünberg Institute, Fundamentals of Future Information Technology, Jülich Aachen Research Alliance, Forschungszentrum Jülich , 52425 Jülich, Germany
| | - Lei Jin
- Peter Grünberg Institute, Fundamentals of Future Information Technology, Jülich Aachen Research Alliance, Forschungszentrum Jülich , 52425 Jülich, Germany
- Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons, Forschungszentrum Jülich , 52425 Jülich, Germany
| | - Chun-Lin Jia
- Peter Grünberg Institute, Fundamentals of Future Information Technology, Jülich Aachen Research Alliance, Forschungszentrum Jülich , 52425 Jülich, Germany
- Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons, Forschungszentrum Jülich , 52425 Jülich, Germany
| | - Regina Dittmann
- Peter Grünberg Institute, Fundamentals of Future Information Technology, Jülich Aachen Research Alliance, Forschungszentrum Jülich , 52425 Jülich, Germany
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21
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Smink AEM, de Boer JC, Stehno MP, Brinkman A, van der Wiel WG, Hilgenkamp H. Gate-Tunable Band Structure of the LaAlO_{3}-SrTiO_{3} Interface. PHYSICAL REVIEW LETTERS 2017; 118:106401. [PMID: 28339281 DOI: 10.1103/physrevlett.118.106401] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/10/2016] [Indexed: 06/06/2023]
Abstract
The two-dimensional electron system at the interface between LaAlO_{3} and SrTiO_{3} has several unique properties that can be tuned by an externally applied gate voltage. In this work, we show that this gate tunability extends to the effective band structure of the system. We combine a magnetotransport study on top-gated Hall bars with self-consistent Schrödinger-Poisson calculations and observe a Lifshitz transition at a density of 2.9×10^{13}cm^{-2}. Above the transition, the carrier density of one of the conducting bands decreases with increasing gate voltage. This surprising decrease is accurately reproduced in the calculations if electronic correlations are included. These results provide a clear, intuitive picture of the physics governing the electronic structure at complex-oxide interfaces.
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Affiliation(s)
- A E M Smink
- MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
| | - J C de Boer
- MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
| | - M P Stehno
- MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
| | - A Brinkman
- MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
| | - W G van der Wiel
- MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
| | - H Hilgenkamp
- MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
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22
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Chen Z, Yuan H, Xie Y, Lu D, Inoue H, Hikita Y, Bell C, Hwang HY. Dual-Gate Modulation of Carrier Density and Disorder in an Oxide Two-Dimensional Electron System. NANO LETTERS 2016; 16:6130-6136. [PMID: 27605459 DOI: 10.1021/acs.nanolett.6b02348] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Carrier density and disorder are two crucial parameters that control the properties of correlated two-dimensional electron systems. In order to disentangle their individual contributions to quantum phenomena, independent tuning of these two parameters is required. Here, by utilizing a hybrid liquid/solid electric dual-gate geometry acting on the conducting LaAlO3/SrTiO3 heterointerface, we obtain an additional degree of freedom to strongly modify the electron confinement profile and thus the strength of interfacial scattering, independent from the carrier density. A dual-gate controlled nonlinear Hall effect is a direct manifestation of this profile, which can be quantitatively understood by a Poisson-Schrödinger sub-band model. In particular, the large nonlinear dielectric response of SrTiO3 enables a very wide range of tunable density and disorder, far beyond that for conventional semiconductors. Our study provides a broad framework for understanding various reported phenomena at the LaAlO3/SrTiO3 interface.
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Affiliation(s)
- Zhuoyu Chen
- Geballe Laboratory for Advanced Materials, Stanford University , Stanford, California 94305, United States
| | - Hongtao Yuan
- 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
| | - Yanwu Xie
- 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
| | - Hisashi Inoue
- Geballe Laboratory for Advanced Materials, Stanford University , Stanford, California 94305, United States
| | - Yasuyuki Hikita
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory , Menlo Park, California 94025, United States
| | - Christopher Bell
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory , Menlo Park, California 94025, United States
- H.H. Wills Physics Laboratory, University of Bristol , Tyndall Avenue, Bristol BS8 1TL, United Kingdom
| | - 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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23
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Yang K, Nazir S, Behtash M, Cheng J. High-Throughput Design of Two-Dimensional Electron Gas Systems Based on Polar/Nonpolar Perovskite Oxide Heterostructures. Sci Rep 2016; 6:34667. [PMID: 27708415 PMCID: PMC5052574 DOI: 10.1038/srep34667] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2016] [Accepted: 09/19/2016] [Indexed: 11/15/2022] Open
Abstract
The two-dimensional electron gas (2DEG) formed at the interface between two insulating oxides such as LaAlO3 and SrTiO3 (STO) is of fundamental and practical interest because of its novel interfacial conductivity and its promising applications in next-generation nanoelectronic devices. Here we show that a group of combinatorial descriptors that characterize the polar character, lattice mismatch, band gap, and the band alignment between the perovskite-oxide-based band insulators and the STO substrate, can be introduced to realize a high-throughput (HT) design of SrTiO3-based 2DEG systems from perovskite oxide quantum database. Equipped with these combinatorial descriptors, we have carried out a HT screening of all the polar perovskite compounds, uncovering 42 compounds of potential interests. Of these, Al-, Ga-, Sc-, and Ta-based compounds can form a 2DEG with STO, while In-based compounds exhibit a strain-induced strong polarization when deposited on STO substrate. In particular, the Ta-based compounds can form 2DEG with potentially high electron mobility at (TaO2)+/(SrO)0 interface. Our approach, by defining materials descriptors solely based on the bulk materials properties, and by relying on the perovskite-oriented quantum materials repository, opens new avenues for the discovery of perovskite-oxide-based functional interface materials in a HT fashion.
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Affiliation(s)
- Kesong Yang
- Department of NanoEngineering, University of California, San Diego, 9500 Gilman Drive, Mail Code 0448, La Jolla, California 92093-0448, USA
| | - Safdar Nazir
- Department of NanoEngineering, University of California, San Diego, 9500 Gilman Drive, Mail Code 0448, La Jolla, California 92093-0448, USA
| | - Maziar Behtash
- Department of NanoEngineering, University of California, San Diego, 9500 Gilman Drive, Mail Code 0448, La Jolla, California 92093-0448, USA
| | - Jianli Cheng
- Department of NanoEngineering, University of California, San Diego, 9500 Gilman Drive, Mail Code 0448, La Jolla, California 92093-0448, USA
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24
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Lee PW, Singh VN, Guo GY, Liu HJ, Lin JC, Chu YH, Chen CH, Chu MW. Hidden lattice instabilities as origin of the conductive interface between insulating LaAlO3 and SrTiO3. Nat Commun 2016; 7:12773. [PMID: 27624682 PMCID: PMC5027288 DOI: 10.1038/ncomms12773] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2016] [Accepted: 08/01/2016] [Indexed: 11/09/2022] Open
Abstract
The metallic interface between insulating LaAlO3 and SrTiO3 opens up the field of oxide electronics. With more than a decade of researches on this heterostructure, the origin of the interfacial conductivity, however, remains unsettled. Here we resolve this long-standing puzzle by atomic-scale observation of electron-gas formation for screening hidden lattice instabilities, rejuvenated near the interface by epitaxial strain. Using atomic-resolution imaging and electron spectroscopy, the generally accepted notions of polar catastrophe and cation intermixing for the metallic interface are discounted. Instead, the conductivity onset at the critical thickness of 4-unit cell LaAlO3 on SrTiO3 substrate is accompanied with head-to-head ferroelectric-like polarizations across the interface due to strain-rejuvenated ferroelectric-like instabilities in the materials. The divergent depolarization fields of the head-to-head polarizations cast the interface into an electron reservoir, forming screening electron gas in SrTiO3 with LaAlO3 hosting complementary localized holes. The ferroelectric-like polarizations and electron–hole juxtaposition reveal the cooperative nature of metallic LaAlO3/SrTiO3. The origin of interfacial conductivity between two insulating oxides, LaAlO3 and SrTiO3, remains elusive despite a long time research. Here, Lee et al. report atomic-scale observation of electron-gas formation for screening hidden ferroelectric-like lattice instabilities, discounting the role of polar catastrophe and cation intermixing.
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Affiliation(s)
- P W Lee
- Department of Physics, National Taiwan University, Taipei 106, Taiwan.,Center for Condensed Matter Sciences, National Taiwan University, Taipei 106, Taiwan
| | - V N Singh
- Department of Physics, National Taiwan University, Taipei 106, Taiwan.,Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 106, Taiwan
| | - G Y Guo
- Department of Physics, National Taiwan University, Taipei 106, Taiwan.,Physics Division, National Center for Theoretical Sciences, Hsinchu 300, Taiwan
| | - H-J Liu
- Department of Materials Science and Engineering, National Chiao Tung University, Hsinchu 300, Taiwan
| | - J-C Lin
- Institute of Physics, Academia Sinica, Taipei 105, Taiwan
| | - Y-H Chu
- Department of Materials Science and Engineering, National Chiao Tung University, Hsinchu 300, Taiwan.,Institute of Physics, Academia Sinica, Taipei 105, Taiwan
| | - C H Chen
- Center for Condensed Matter Sciences, National Taiwan University, Taipei 106, Taiwan.,Department of Physics and Astronomy, Rutgers University, Piscataway, New Jersey 08854, USA
| | - M-W Chu
- Center for Condensed Matter Sciences, National Taiwan University, Taipei 106, Taiwan
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25
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Dai W, Adhikari S, Garcia-Castro AC, Romero AH, Lee H, Lee JW, Ryu S, Eom CB, Cen C. Tailoring LaAlO3/SrTiO3 Interface Metallicity by Oxygen Surface Adsorbates. NANO LETTERS 2016; 16:2739-2743. [PMID: 26928809 DOI: 10.1021/acs.nanolett.6b00421] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
We report an oxygen surface adsorbates induced metal-insulator transition at the LaAlO3/SrTiO3 interfaces. The observed effects were attributed to the terminations of surface Al sites and the resultant electron-accepting surface states. By controlling the local oxygen adsorptions, we successfully demonstrated the nondestructive patterning of the interface two-dimensional electron gas (2DEG). The obtained 2DEG structures are stable in air and also robust against general solvent treatments. This study provides new insights into the metal-insulator transition mechanism at the complex oxide interfaces and also a highly efficient technique for tailoring the interface properties.
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Affiliation(s)
- Weitao Dai
- Department of Physics and Astronomy, West Virginia University , Morgantown, West Virginia 26506, United States
| | - Sanjay Adhikari
- Department of Physics and Astronomy, West Virginia University , Morgantown, West Virginia 26506, United States
| | - Andrés Camilo Garcia-Castro
- Physique Théorique des Matériaux, Université de Liège , B-4000 Sart-Tilman, Belgium
- Centro de Investigación y Estudios Avanzados del IPN , MX-76230 Querétaro, México
| | - Aldo H Romero
- Department of Physics and Astronomy, West Virginia University , Morgantown, West Virginia 26506, United States
| | - Hyungwoo Lee
- Department of Material Science and Engineering, University of Wisconsin-Madison , Madison, Wisconsin 53706, United States
| | - Jung-Woo Lee
- Department of Material Science and Engineering, University of Wisconsin-Madison , Madison, Wisconsin 53706, United States
| | - Sangwoo Ryu
- Department of Material Science and Engineering, University of Wisconsin-Madison , Madison, Wisconsin 53706, United States
| | - Chang-Beom Eom
- Department of Material Science and Engineering, University of Wisconsin-Madison , Madison, Wisconsin 53706, United States
| | - Cheng Cen
- Department of Physics and Astronomy, West Virginia University , Morgantown, West Virginia 26506, United States
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26
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Hurand S, Jouan A, Feuillet-Palma C, Singh G, Biscaras J, Lesne E, Reyren N, Barthélémy A, Bibes M, Villegas JE, Ulysse C, Lafosse X, Pannetier-Lecoeur M, Caprara S, Grilli M, Lesueur J, Bergeal N. Field-effect control of superconductivity and Rashba spin-orbit coupling in top-gated LaAlO3/SrTiO3 devices. Sci Rep 2015; 5:12751. [PMID: 26244916 PMCID: PMC4525493 DOI: 10.1038/srep12751] [Citation(s) in RCA: 73] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2015] [Accepted: 07/06/2015] [Indexed: 11/18/2022] Open
Abstract
The recent development in the fabrication of artificial oxide heterostructures opens new avenues in the field of quantum materials by enabling the manipulation of the charge, spin and orbital degrees of freedom. In this context, the discovery of two-dimensional electron gases (2-DEGs) at LaAlO3/SrTiO3 interfaces, which exhibit both superconductivity and strong Rashba spin-orbit coupling (SOC), represents a major breakthrough. Here, we report on the realisation of a field-effect LaAlO3/SrTiO3 device, whose physical properties, including superconductivity and SOC, can be tuned over a wide range by a top-gate voltage. We derive a phase diagram, which emphasises a field-effect-induced superconductor-to-insulator quantum phase transition. Magneto-transport measurements show that the Rashba coupling constant increases linearly with the interfacial electric field. Our results pave the way for the realisation of mesoscopic devices, where these two properties can be manipulated on a local scale by means of top-gates.
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Affiliation(s)
- S Hurand
- Laboratoire de Physique et d'Etude des Matériaux -CNRS-ESPCI ParisTech-UPMC, PSL Research University, 10 Rue Vauquelin, 75005 Paris, France
| | - A Jouan
- Laboratoire de Physique et d'Etude des Matériaux -CNRS-ESPCI ParisTech-UPMC, PSL Research University, 10 Rue Vauquelin, 75005 Paris, France
| | - C Feuillet-Palma
- Laboratoire de Physique et d'Etude des Matériaux -CNRS-ESPCI ParisTech-UPMC, PSL Research University, 10 Rue Vauquelin, 75005 Paris, France
| | - G Singh
- Laboratoire de Physique et d'Etude des Matériaux -CNRS-ESPCI ParisTech-UPMC, PSL Research University, 10 Rue Vauquelin, 75005 Paris, France
| | - J Biscaras
- Laboratoire de Physique et d'Etude des Matériaux -CNRS-ESPCI ParisTech-UPMC, PSL Research University, 10 Rue Vauquelin, 75005 Paris, France
| | - E Lesne
- Unité Mixte de Physique CNRS-Thales, 1 Av. A. Fresnel, 91767 Palaiseau, France
| | - N Reyren
- Unité Mixte de Physique CNRS-Thales, 1 Av. A. Fresnel, 91767 Palaiseau, France
| | - A Barthélémy
- Unité Mixte de Physique CNRS-Thales, 1 Av. A. Fresnel, 91767 Palaiseau, France
| | - M Bibes
- Unité Mixte de Physique CNRS-Thales, 1 Av. A. Fresnel, 91767 Palaiseau, France
| | - J E Villegas
- Unité Mixte de Physique CNRS-Thales, 1 Av. A. Fresnel, 91767 Palaiseau, France
| | - C Ulysse
- Laboratoire de Photonique et de Nanostructures LPN-CNRS, Route de Nozay, 91460 Marcoussis, France
| | - X Lafosse
- Laboratoire de Photonique et de Nanostructures LPN-CNRS, Route de Nozay, 91460 Marcoussis, France
| | - M Pannetier-Lecoeur
- DSM/IRAMIS/SPEC - CNRS UMR 3680, CEA Saclay, F-91191 Gif sur Yvette Cedex, France
| | - S Caprara
- Dipartimento di Fisica Università di Roma "La Sapienza", piazzale Aldo Moro 5, I-00185 Roma, Italy
| | - M Grilli
- Dipartimento di Fisica Università di Roma "La Sapienza", piazzale Aldo Moro 5, I-00185 Roma, Italy
| | - J Lesueur
- Laboratoire de Physique et d'Etude des Matériaux -CNRS-ESPCI ParisTech-UPMC, PSL Research University, 10 Rue Vauquelin, 75005 Paris, France
| | - N Bergeal
- Laboratoire de Physique et d'Etude des Matériaux -CNRS-ESPCI ParisTech-UPMC, PSL Research University, 10 Rue Vauquelin, 75005 Paris, France
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27
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Gariglio S, Fête A, Triscone JM. Electron confinement at the LaAlO3/SrTiO3 interface. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2015; 27:283201. [PMID: 26102193 DOI: 10.1088/0953-8984/27/28/283201] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Physical and structural phenomena originating from polar discontinuities have generated enormous activity. In the last ten years, the oxide interface between polar LaAlO(3) and non-polar SrTiO(3), both band insulators, has attracted particular interest, as it hosts an electron liquid with remarkable properties: it superconducts, has a sizeable spin-orbit interaction and its properties are tunable by an electric field. The profile of the carrier density at the interface and the exact band structure are properties strongly linked and still objects of debate. Here we review the experimental findings on the origin and the extension of the electron liquid and discuss the theoretical models developed to describe the charge profile and the band structure. We also introduce a model to account for the effect of interface disorder which could modify the charge distribution.
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Affiliation(s)
- S Gariglio
- DQMP, Université de Genève, 24 Quai E.-Ansermet, CH-1211 Genève, Switzerland
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28
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Rotella H, Copie O, Pautrat A, Boullay P, David A, Pelloquin D, Labbé C, Frilay C, Prellier W. Two components for one resistivity in LaVO3/SrTiO3 heterostructure. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2015; 27:095603. [PMID: 25688927 DOI: 10.1088/0953-8984/27/9/095603] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
A series of 100 nm LaVO3 thin films have been synthesized on (0 0 1)-oriented SrTiO3 substrates using the pulsed laser deposition technique, and the effects of growth temperature are analyzed. Transport properties reveal a large electronic mobility and a non-linear Hall effect at low temperature. In addition, a cross-over from a semiconducting state at high-temperature to a metallic state at low-temperature is observed, with a clear enhancement of the metallic character as the growth temperature increases. Optical absorption measurements combined with the two-bands analysis of the Hall effect show that the metallicity is induced by the diffusion of oxygen vacancies in the SrTiO3 substrate. These results allow us to understand that the film/substrate heterostructure behaves as an original semiconducting-metallic parallel resistor, and electronic transport properties are consistently explained.
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Affiliation(s)
- H Rotella
- Laboratoire CRISMAT, CNRS UMR 6508, ENSICAEN et Université de Caen, 6 Bd Maréchal Juin, 14050 Caen Cedex 4, France. NUSNNI-NanoCore, National University of Singapore, 117411 Singapore
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29
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Biscaras J, Hurand S, Feuillet-Palma C, Rastogi A, Budhani RC, Reyren N, Lesne E, Lesueur J, Bergeal N. Limit of the electrostatic doping in two-dimensional electron gases of LaXO₃(X = Al, Ti)/SrTiO₃. Sci Rep 2014; 4:6788. [PMID: 25346028 PMCID: PMC4209450 DOI: 10.1038/srep06788] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2014] [Accepted: 10/06/2014] [Indexed: 11/15/2022] Open
Abstract
In LaTiO3/SrTiO3 and LaAlO3/SrTiO3 heterostructures, the bending of the SrTiO3 conduction band at the interface forms a quantum well that contains a superconducting two-dimensional electron gas (2-DEG). Its carrier density and electronic properties, such as superconductivity and Rashba spin-orbit coupling can be controlled by electrostatic gating. In this article we show that the Fermi energy lies intrinsically near the top of the quantum well. Beyond a filling threshold, electrons added by electrostatic gating escape from the well, hence limiting the possibility to reach a highly-doped regime. This leads to an irreversible doping regime where all the electronic properties of the 2-DEG, such as its resistivity and its superconducting transition temperature, saturate. The escape mechanism can be described by the simple analytical model we propose.
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Affiliation(s)
- J Biscaras
- LPEM- UMR8213/CNRS - ESPCI ParisTech - UPMC, 10 rue Vauquelin - 75005 Paris, France
| | - S Hurand
- LPEM- UMR8213/CNRS - ESPCI ParisTech - UPMC, 10 rue Vauquelin - 75005 Paris, France
| | - C Feuillet-Palma
- LPEM- UMR8213/CNRS - ESPCI ParisTech - UPMC, 10 rue Vauquelin - 75005 Paris, France
| | - A Rastogi
- Condensed Matter - Low Dimensional Systems Laboratory, Department of Physics, Indian Institute of Technology Kanpur, Kanpur 208016, India
| | - R C Budhani
- 1] Condensed Matter - Low Dimensional Systems Laboratory, Department of Physics, Indian Institute of Technology Kanpur, Kanpur 208016, India [2] National Physical Laboratory, New Delhi - 110012, India and
| | - N Reyren
- Unité Mixte de Physique CNRS-Thales, 1 Av. A. Fresnel, 91767 Palaiseau, France
| | - E Lesne
- Unité Mixte de Physique CNRS-Thales, 1 Av. A. Fresnel, 91767 Palaiseau, France
| | - J Lesueur
- LPEM- UMR8213/CNRS - ESPCI ParisTech - UPMC, 10 rue Vauquelin - 75005 Paris, France
| | - N Bergeal
- LPEM- UMR8213/CNRS - ESPCI ParisTech - UPMC, 10 rue Vauquelin - 75005 Paris, France
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30
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Walker SM, de la Torre A, Bruno FY, Tamai A, Kim TK, Hoesch M, Shi M, Bahramy MS, King PDC, Baumberger F. Control of a two-dimensional electron gas on SrTiO₃(111) by atomic oxygen. PHYSICAL REVIEW LETTERS 2014; 113:177601. [PMID: 25379937 DOI: 10.1103/physrevlett.113.177601] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/12/2014] [Indexed: 06/04/2023]
Abstract
We report on the formation of a two-dimensional electron gas (2DEG) at the bare surface of (111) oriented SrTiO3. Angle resolved photoemission experiments reveal highly itinerant carriers with a sixfold symmetric Fermi surface and strongly anisotropic effective masses. The electronic structure of the 2DEG is in good agreement with self-consistent tight-binding supercell calculations that incorporate a confinement potential due to surface band bending. We further demonstrate that alternate exposure of the surface to ultraviolet light and atomic oxygen allows tuning of the carrier density and the complete suppression of the 2DEG.
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Affiliation(s)
- S McKeown Walker
- Département de Physique de la Matière Condensée, Universitée de Genève, 24 Quai Ernest-Ansermet, 1211 Genève 4, Switzerland
| | - A de la Torre
- Département de Physique de la Matière Condensée, Universitée de Genève, 24 Quai Ernest-Ansermet, 1211 Genève 4, Switzerland
| | - F Y Bruno
- Département de Physique de la Matière Condensée, Universitée de Genève, 24 Quai Ernest-Ansermet, 1211 Genève 4, Switzerland
| | - A Tamai
- Département de Physique de la Matière Condensée, Universitée de Genève, 24 Quai Ernest-Ansermet, 1211 Genève 4, Switzerland
| | - T K Kim
- Diamond Light Source, Harwell Campus, Didcot OX11 0DE, United Kingdom
| | - M Hoesch
- Diamond Light Source, Harwell Campus, Didcot OX11 0DE, United Kingdom
| | - M Shi
- Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
| | - M S Bahramy
- Quantum-Phase Electronics Center, Department of Applied Physics, The University of Tokyo, Tokyo 113-8656, Japan and RIKEN Center for Emergent Matter Science (CEMS), Wako 351-0198, Japan
| | - P D C King
- SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews, Fife KY16 9SS, United Kingdom
| | - F Baumberger
- Département de Physique de la Matière Condensée, Universitée de Genève, 24 Quai Ernest-Ansermet, 1211 Genève 4, Switzerland and Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland and SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews, Fife KY16 9SS, United Kingdom
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31
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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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32
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Bibes M, Reyren N, Lesne E, George JM, Deranlot C, Collin S, Barthélémy A, Jaffrès H. Towards electrical spin injection into LaAlO3-SrTiO3. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2012; 370:4958-4971. [PMID: 22987038 DOI: 10.1098/rsta.2012.0201] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Future spintronics devices will be built from elemental blocks allowing the electrical injection, propagation, manipulation and detection of spin-based information. Owing to their remarkable multi-functional and strongly correlated character, oxide materials already provide such building blocks for charge-based devices such as ferroelectric field-effect transistors (FETs), as well as for spin-based two-terminal devices such as magnetic tunnel junctions, with giant responses in both cases. Until now, the lack of suitable channel materials and the uncertainty of spin-injection conditions in these compounds had however prevented the exploration of similar giant responses in oxide-based lateral spin transport structures. In this paper, we discuss the potential of oxide-based spin FETs and report magnetotransport data that suggest electrical spin injection into the LaAlO(3)-SrTiO(3) interface system. In a local, three-terminal measurement scheme, we analyse the voltage variation associated with the precession of the injected spin accumulation driven by perpendicular or longitudinal magnetic fields (Hanle and 'inverted' Hanle effects). The spin accumulation signal appears to be much larger than expected, probably owing to amplification effects by resonant tunnelling through localized states in the LaAlO(3). We give perspectives on how to achieve direct spin injection with increased detection efficiency, as well on the implementation of efficient top gating schemes for spin manipulation.
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Affiliation(s)
- M Bibes
- Unité Mixte de Physique CNRS-Thales, Palaiseau, France.
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33
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Biscaras J, Bergeal N, Hurand S, Grossetête C, Rastogi A, Budhani RC, LeBoeuf D, Proust C, Lesueur J. Two-dimensional superconducting phase in LaTiO3/SrTiO3 heterostructures induced by high-mobility carrier doping. PHYSICAL REVIEW LETTERS 2012; 108:247004. [PMID: 23004312 DOI: 10.1103/physrevlett.108.247004] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/16/2011] [Indexed: 06/01/2023]
Abstract
In this Letter, we show that a superconducting two-dimensional electron gas is formed at the LaTiO3/SrTiO3 interface whose transition temperature can be modulated by a back-gate voltage. The gas consists of two types of carriers: a majority of low-mobility carriers always present, and a few high-mobility ones that can be injected by electrostatic doping. The calculation of the electron spatial distribution in the confinement potential shows that the high-mobility electrons responsible for superconductivity set at the edge of the gas whose extension can be tuned by the field effect.
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Affiliation(s)
- J Biscaras
- LPEM-UMR8213/CNRS-ESPCI ParisTech-UPMC, 10 rue Vauquelin-75005 Paris, France
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34
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Reyren N, Bibes M, Lesne E, George JM, Deranlot C, Collin S, Barthélémy A, Jaffrès H. Gate-controlled spin injection at LaAlO3/SrTiO3 interfaces. PHYSICAL REVIEW LETTERS 2012; 108:186802. [PMID: 22681101 DOI: 10.1103/physrevlett.108.186802] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/25/2011] [Indexed: 06/01/2023]
Abstract
We report results of electrical spin injection at the high-mobility quasi-two-dimensional electron system (2-DES) that forms at the LaAlO3/SrTiO3 interface. In a nonlocal, three-terminal measurement geometry, we analyze the voltage variation associated with the precession of the injected spin accumulation driven by perpendicular or transverse magnetic fields (Hanle and inverted Hanle effect). The influence of bias and back-gate voltages reveals that the spin accumulation signal is amplified by resonant tunneling through localized states in the LaAlO3 strongly coupled to the 2-DES by tunneling transfer.
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Affiliation(s)
- N Reyren
- Unité Mixte de Physique CNRS-Thales, 1 Av. A. Fresnel, 91767 Palaiseau, France
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35
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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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36
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Yamamoto R, Bell C, Hikita Y, Hwang HY, Nakamura H, Kimura T, Wakabayashi Y. Structural comparison of n-type and p-type LaAlO3/SrTiO3 interfaces. PHYSICAL REVIEW LETTERS 2011; 107:036104. [PMID: 21838380 DOI: 10.1103/physrevlett.107.036104] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/16/2011] [Indexed: 05/31/2023]
Abstract
Using a surface x-ray diffraction technique, we investigated the atomic structure of two types of interfaces between LaAlO3 and SrTiO3, that is, p-type (SrO/AlO2) and n-type (TiO2/LaO) interfaces. Our results demonstrate that the SrTiO3 in the sample with the n-type interface has a large polarized region, while that with the p-type interface has a limited polarized region. In addition, atomic intermixing was observed to extend deeper into the SrTiO3 substrate at the n-type interface compared to the p type. These differences result in distinct degrees of band bending, which likely contributes to the striking contrast in electrical conductivity between the two types of interfaces.
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Affiliation(s)
- Ryosuke Yamamoto
- Division of Materials Physics, Graduate School of Engineering Science, Osaka University, Toyonaka 560-8531, Japan
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37
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Delugas P, Filippetti A, Fiorentini V, Bilc DI, Fontaine D, Ghosez P. Spontaneous 2-dimensional carrier confinement at the n-type SrTiO3/LaAlO3 interface. PHYSICAL REVIEW LETTERS 2011; 106:166807. [PMID: 21599400 DOI: 10.1103/physrevlett.106.166807] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/22/2010] [Indexed: 05/30/2023]
Abstract
We describe the intrinsic mechanism of 2-dimensional electron confinement at the n-type SrTiO3/LaAlO3 interface as a function of the sheet carrier density n(s) via advanced first-principles calculations. Electrons localize spontaneously in Ti 3d(xy) levels within a thin (≲2 nm) interface-adjacent SrTiO3 region for n(s) lower than a threshold value n(c)∼10(14) cm(-2). For n(s)>n(c) a portion of charge flows into Ti 3d(xz)-d(yz) levels extending farther from the interface. This intrinsic confinement can be attributed to the interface-induced symmetry breaking and localized nature of Ti 3d t(2g) states. The sheet carrier density directly controls the binding energy and the spatial extension of the conductive region. A direct, quantitative relation of these quantities with n(s) is provided.
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Affiliation(s)
- Pietro Delugas
- CNR-IOM UOS Cagliari, Dipartimento di Fisica, Università di Cagliari, Monserrato (CA), Italy
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38
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Stengel M. First-principles modeling of electrostatically doped perovskite systems. PHYSICAL REVIEW LETTERS 2011; 106:136803. [PMID: 21517406 DOI: 10.1103/physrevlett.106.136803] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/11/2010] [Indexed: 05/30/2023]
Abstract
Macroscopically, confined electron gases at polar oxide interfaces are rationalized within the simple "polar catastrophe" model. At the microscopic level, however, many other effects such as electric fields, structural distortions and quantum-mechanical interactions enter into play. Here, we show how to bridge the gap between these two length scales, by combining the accuracy of first-principles methods with the conceptual simplicity of model Hamiltonian approaches. To demonstrate our strategy, we address the equilibrium distribution of the compensating free carriers at polar LaAlO(3)/SrTiO(3) interfaces. Remarkably, a model including only calculated bulk properties of SrTiO(3) and no adjustable parameters accurately reproduces our full first-principles results. Our strategy provides a unified description of charge compensation mechanisms in SrTiO(3)-based systems.
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Affiliation(s)
- Massimiliano Stengel
- Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Campus UAB, 08193 Bellaterra, Spain.
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39
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Two-dimensional electron gas with universal subbands at the surface of SrTiO(3). Nature 2011; 469:189-93. [PMID: 21228872 DOI: 10.1038/nature09720] [Citation(s) in RCA: 228] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2010] [Accepted: 11/26/2010] [Indexed: 11/08/2022]
Abstract
As silicon is the basis of conventional electronics, so strontium titanate (SrTiO(3)) is the foundation of the emerging field of oxide electronics. SrTiO(3) is the preferred template for the creation of exotic, two-dimensional (2D) phases of electron matter at oxide interfaces that have metal-insulator transitions, superconductivity or large negative magnetoresistance. However, the physical nature of the electronic structure underlying these 2D electron gases (2DEGs), which is crucial to understanding their remarkable properties, remains elusive. Here we show, using angle-resolved photoemission spectroscopy, that there is a highly metallic universal 2DEG at the vacuum-cleaved surface of SrTiO(3) (including the non-doped insulating material) independently of bulk carrier densities over more than seven decades. This 2DEG is confined within a region of about five unit cells and has a sheet carrier density of ∼0.33 electrons per square lattice parameter. The electronic structure consists of multiple subbands of heavy and light electrons. The similarity of this 2DEG to those reported in SrTiO(3)-based heterostructures and field-effect transistors suggests that different forms of electron confinement at the surface of SrTiO(3) lead to essentially the same 2DEG. Our discovery provides a model system for the study of the electronic structure of 2DEGs in SrTiO(3)-based devices and a novel means of generating 2DEGs at the surfaces of transition-metal oxides.
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40
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Meevasana W, King PDC, He RH, Mo SK, Hashimoto M, Tamai A, Songsiriritthigul P, Baumberger F, Shen ZX. Creation and control of a two-dimensional electron liquid at the bare SrTiO3 surface. NATURE MATERIALS 2011; 10:114-8. [PMID: 21240289 DOI: 10.1038/nmat2943] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/15/2010] [Accepted: 12/10/2010] [Indexed: 05/24/2023]
Abstract
Many-body interactions in transition-metal oxides give rise to a wide range of functional properties, such as high-temperature superconductivity, colossal magnetoresistance or multiferroicity . The seminal recent discovery of a two-dimensional electron gas (2DEG) at the interface of the insulating oxides LaAlO(3) and SrTiO(3) (ref. 4) represents an important milestone towards exploiting such properties in all-oxide devices. This conducting interface shows a number of appealing properties, including a high electron mobility, superconductivity and large magnetoresistance, and can be patterned on the few-nanometre length scale. However, the microscopic origin of the interface 2DEG is poorly understood. Here, we show that a similar 2DEG, with an electron density as large as 8×10(13) cm(-2), can be formed at the bare SrTiO(3) surface. Furthermore, we find that the 2DEG density can be controlled through exposure of the surface to intense ultraviolet light. Subsequent angle-resolved photoemission spectroscopy measurements reveal an unusual coexistence of a light quasiparticle mass and signatures of strong many-body interactions.
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Affiliation(s)
- W Meevasana
- Department of Physics, Stanford University, California 94305, USA
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41
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Caviglia AD, Gariglio S, Cancellieri C, Sacépé B, Fête A, Reyren N, Gabay M, Morpurgo AF, Triscone JM. Two-dimensional quantum oscillations of the conductance at LaAlO3/SrTiO3 interfaces. PHYSICAL REVIEW LETTERS 2010; 105:236802. [PMID: 21231492 DOI: 10.1103/physrevlett.105.236802] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/28/2010] [Indexed: 05/30/2023]
Abstract
We report on a study of magnetotransport in LaAlO3 /SrTiO3 interfaces characterized by mobilities of the order of several thousands cm2/V s. We observe Shubnikov-de Haas oscillations whose period depends only on the perpendicular component of the magnetic field. This observation directly indicates the formation of a two-dimensional electron gas originating from quantum confinement at the interface. From the temperature dependence of the oscillation amplitude we extract an effective carrier mass m* ≃ 1.45 m(e). An electric field applied in the back-gate geometry increases the mobility, the carrier density, and the oscillation frequency.
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Affiliation(s)
- A D Caviglia
- Département de Physique de la Matière Condensée, University of Geneva, 24 Quai Ernest-Ansermet, 1211 Genève 4, Switzerland
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42
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Ben Shalom M, Ron A, Palevski A, Dagan Y. Shubnikov-de Haas oscillations in SrTiO3/LaAlO3 interface. PHYSICAL REVIEW LETTERS 2010; 105:206401. [PMID: 21231249 DOI: 10.1103/physrevlett.105.206401] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/29/2010] [Indexed: 05/30/2023]
Abstract
Quantum magnetic oscillations in SrTiO3/LaAlO3 interface are observed in the magnetoresistance. We study their frequency as a function of gate voltage and the evolution of their amplitude with temperature. The data are consistent with the Shubnikov-de Haas theory. The Hall resistivity ρ(xy) is nonlinear at low magnetic fields. ρ(xy) is fitted assuming multiple carrier contributions. We infer the density of the mobile charge carriers from the oscillations frequency and from Hall measurements. The comparison between these densities suggests multiple valley and spin degeneracy. The small amplitude of the oscillation is discussed in the framework of the multiple band scenario.
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Affiliation(s)
- M Ben Shalom
- Raymond and Beverly Sackler School of Physics and Astronomy, Tel-Aviv University, Tel Aviv, 69978, Israel
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43
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Biscaras J, Bergeal N, Kushwaha A, Wolf T, Rastogi A, Budhani R, Lesueur J. Two-dimensional superconductivity at a Mott insulator/band insulator interface LaTiO3/SrTiO3. Nat Commun 2010; 1:89. [DOI: 10.1038/ncomms1084] [Citation(s) in RCA: 221] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2010] [Accepted: 09/06/2010] [Indexed: 11/09/2022] Open
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44
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Dubroka A, Rössle M, Kim KW, Malik VK, Schultz L, Thiel S, Schneider CW, Mannhart J, Herranz G, Copie O, Bibes M, Barthélémy A, Bernhard C. Dynamical response and confinement of the electrons at the LaAlO3/SrTiO3 interface. PHYSICAL REVIEW LETTERS 2010; 104:156807. [PMID: 20482010 DOI: 10.1103/physrevlett.104.156807] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/02/2009] [Indexed: 05/29/2023]
Abstract
With infrared ellipsometry and transport measurements we investigated the electrons at the interface between LaAlO3 and SrTiO3. We obtained a sheet carrier concentration of N(s) approximately = 5-9x10(13) cm(-2), an effective mass of m*=3.2+/-0.4m(e), and a strongly frequency dependent mobility. The latter are similar as in bulk SrTi(1-x)Nb(x)O3 and therefore suggestive of polaronic correlations. We also determined the vertical concentration profile which has a strongly asymmetric shape with a rapid initial decay over the first 2 nm and a pronounced tail that extends to about 11 nm.
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Affiliation(s)
- A Dubroka
- University of Fribourg, Department of Physics and Fribourg Center for Nanomaterials, Chemin du Musée 3, CH-1700 Fribourg, Switzerland
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45
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Caviglia AD, Gabay M, Gariglio S, Reyren N, Cancellieri C, Triscone JM. Tunable Rashba spin-orbit interaction at oxide interfaces. PHYSICAL REVIEW LETTERS 2010; 104:126803. [PMID: 20366557 DOI: 10.1103/physrevlett.104.126803] [Citation(s) in RCA: 215] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/11/2010] [Indexed: 05/29/2023]
Abstract
The quasi-two-dimensional electron gas found at the LaAlO{3}/SrTiO{3} interface offers exciting new functionalities, such as tunable superconductivity, and has been proposed as a new nanoelectronics fabrication platform. Here we lay out a new example of an electronic property arising from the interfacial breaking of inversion symmetry, namely, a large Rashba spin-orbit interaction, whose magnitude can be modulated by the application of an external electric field. By means of magnetotransport experiments we explore the evolution of the spin-orbit coupling across the phase diagram of the system. We uncover a steep rise in Rashba interaction occurring around the doping level where a quantum critical point separates the insulating and superconducting ground states of the system.
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Affiliation(s)
- A D Caviglia
- Département de Physique de la Matière Condensée, University of Geneva, 24 Quai Ernest-Ansermet, 1211 Genève 4, Switzerland
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