1
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Omar GJ, Kong WL, Jani H, Li MS, Zhou J, Lim ZS, Prakash S, Zeng SW, Hooda S, Venkatesan T, Feng YP, Pennycook SJ, Shen L, Ariando A. Experimental Evidence of t_{2g} Electron-Gas Rashba Interaction Induced by Asymmetric Orbital Hybridization. Phys Rev Lett 2022; 129:187203. [PMID: 36374676 DOI: 10.1103/physrevlett.129.187203] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/23/2021] [Accepted: 09/28/2022] [Indexed: 06/16/2023]
Abstract
We report the control of Rashba spin-orbit interaction by tuning asymmetric hybridization between Ti orbitals at the LaAlO_{3}/SrTiO_{3} interface. This asymmetric orbital hybridization is modulated by introducing a LaFeO_{3} layer between LaAlO_{3} and SrTiO_{3}, which alters the Ti-O lattice polarization and traps interfacial charge carriers, resulting in a large Rashba spin-orbit effect at the interface in the absence of an external bias. This observation is verified through high-resolution electron microscopy, magnetotransport and first-principles calculations. Our results open hitherto unexplored avenues of controlling Rashba interaction to design next-generation spin orbitronics.
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Affiliation(s)
- G J Omar
- Department of Physics, Faculty of Science, National University of Singapore, Singapore 117542, Singapore
| | - W L Kong
- Department of Mechanical Engineering, National University of Singapore, Singapore 117575, Singapore
| | - H Jani
- Department of Physics, Faculty of Science, National University of Singapore, Singapore 117542, Singapore
| | - M S Li
- Department of Materials Science and Engineering, National University of Singapore, Singapore, 117575
| | - J Zhou
- Department of Physics, Faculty of Science, National University of Singapore, Singapore 117542, Singapore
| | - Z S Lim
- Department of Physics, Faculty of Science, National University of Singapore, Singapore 117542, Singapore
| | - S Prakash
- Department of Physics, Faculty of Science, National University of Singapore, Singapore 117542, Singapore
| | - S W Zeng
- Department of Physics, Faculty of Science, National University of Singapore, Singapore 117542, Singapore
| | - S Hooda
- Department of Electrical and Computer Engineering, National University of Singapore, Singapore 117576, Singapore
| | - T Venkatesan
- Department of Electrical and Computer Engineering, National University of Singapore, Singapore 117576, Singapore
| | - Y P Feng
- Department of Physics, Faculty of Science, National University of Singapore, Singapore 117542, Singapore
| | - S J Pennycook
- Department of Materials Science and Engineering, National University of Singapore, Singapore, 117575
| | - L Shen
- Department of Mechanical Engineering, National University of Singapore, Singapore 117575, Singapore
| | - A Ariando
- Department of Physics, Faculty of Science, National University of Singapore, Singapore 117542, Singapore
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2
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Zeng SW, Yin XM, Herng TS, Han K, Huang Z, Zhang LC, Li CJ, Zhou WX, Wan DY, Yang P, Ding J, Wee ATS, Coey JMD, Venkatesan T, Rusydi A, Ariando A. Oxygen Electromigration and Energy Band Reconstruction Induced by Electrolyte Field Effect at Oxide Interfaces. Phys Rev Lett 2018; 121:146802. [PMID: 30339445 DOI: 10.1103/physrevlett.121.146802] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/28/2017] [Indexed: 06/08/2023]
Abstract
Electrolyte gating is a powerful means for tuning the carrier density and exploring the resultant modulation of novel properties on solid surfaces. However, the mechanism, especially its effect on the oxygen migration and electrostatic charging at the oxide heterostructures, is still unclear. Here we explore the electrolyte gating on oxygen-deficient interfaces between SrTiO_{3} (STO) crystals and LaAlO_{3} (LAO) overlayer through the measurements of electrical transport, x-ray absorption spectroscopy, and photoluminescence spectra. We found that oxygen vacancies (O_{vac}) were filled selectively and irreversibly after gating due to oxygen electromigration at the amorphous LAO/STO interface, resulting in a reconstruction of its interfacial band structure. Because of the filling of O_{vac}, the amorphous interface also showed an enhanced electron mobility and quantum oscillation of the conductance. Further, the filling effect could be controlled by the degree of the crystallinity of the LAO overlayer by varying the growth temperatures. Our results reveal the different effects induced by electrolyte gating, providing further clues to understand the mechanism of electrolyte gating on buried interfaces and also opening a new avenue for constructing high-mobility oxide interfaces.
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Affiliation(s)
- S W Zeng
- NUSNNI-NanoCore, National University of Singapore, Singapore 117411, Singapore
- Department of Physics, National University of Singapore, Singapore 117542, Singapore
| | - X M Yin
- Department of Physics, National University of Singapore, Singapore 117542, Singapore
- Singapore Synchrotron Light Source (SSLS), National University of Singapore, 5 Research Link, Singapore 117603, Singapore
- SZU-NUS Collaborative Innovation Center for Optoelectronic Science & Technology, Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Optoelectronic Engineering, Shenzhen University, Shenzhen 518060, China
| | - T S Herng
- Department of Materials Science and Engineering, National University of Singapore, Singapore 117576, Singapore
| | - K Han
- NUSNNI-NanoCore, National University of Singapore, Singapore 117411, Singapore
- Department of Physics, National University of Singapore, Singapore 117542, Singapore
| | - Z Huang
- NUSNNI-NanoCore, National University of Singapore, Singapore 117411, Singapore
- Department of Physics, National University of Singapore, Singapore 117542, Singapore
| | - L C Zhang
- NUSNNI-NanoCore, National University of Singapore, Singapore 117411, Singapore
- Department of Physics, National University of Singapore, Singapore 117542, Singapore
| | - C J Li
- NUSNNI-NanoCore, National University of Singapore, Singapore 117411, Singapore
- Department of Materials Science and Engineering, National University of Singapore, Singapore 117576, Singapore
| | - W X Zhou
- NUSNNI-NanoCore, National University of Singapore, Singapore 117411, Singapore
- Department of Physics, National University of Singapore, Singapore 117542, Singapore
| | - D Y Wan
- NUSNNI-NanoCore, National University of Singapore, Singapore 117411, Singapore
- Department of Physics, National University of Singapore, Singapore 117542, Singapore
| | - P Yang
- Singapore Synchrotron Light Source (SSLS), National University of Singapore, 5 Research Link, Singapore 117603, Singapore
| | - J Ding
- NUSNNI-NanoCore, National University of Singapore, Singapore 117411, Singapore
- Department of Materials Science and Engineering, National University of Singapore, Singapore 117576, Singapore
| | - A T S Wee
- Department of Physics, National University of Singapore, Singapore 117542, Singapore
- Centre for Advanced 2D Materials and Graphene Research, National University of Singapore, Singapore 117546, Singapore
| | - J M D Coey
- NUSNNI-NanoCore, National University of Singapore, Singapore 117411, Singapore
- School of Physics and CRANN, Trinity College, Dublin 2, Ireland
| | - T Venkatesan
- NUSNNI-NanoCore, National University of Singapore, Singapore 117411, Singapore
- Department of Physics, National University of Singapore, Singapore 117542, Singapore
- Department of Materials Science and Engineering, National University of Singapore, Singapore 117576, Singapore
- Department of Electrical and Computer Engineering, National University of Singapore, Singapore 117576, Singapore
- National University of Singapore Graduate School for Integrative Sciences and Engineering (NGS), 28 Medical Drive, Singapore 117456, Singapore
| | - A Rusydi
- NUSNNI-NanoCore, National University of Singapore, Singapore 117411, Singapore
- Department of Physics, National University of Singapore, Singapore 117542, Singapore
- Singapore Synchrotron Light Source (SSLS), National University of Singapore, 5 Research Link, Singapore 117603, Singapore
| | - A Ariando
- NUSNNI-NanoCore, National University of Singapore, Singapore 117411, Singapore
- Department of Physics, National University of Singapore, Singapore 117542, Singapore
- National University of Singapore Graduate School for Integrative Sciences and Engineering (NGS), 28 Medical Drive, Singapore 117456, Singapore
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3
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Zheng LM, Wang XR, Lü WM, Li CJ, Paudel TR, Liu ZQ, Huang Z, Zeng SW, Han K, Chen ZH, Qiu XP, Li MS, Yang S, Yang B, Chisholm MF, Martin LW, Pennycook SJ, Tsymbal EY, Coey JMD, Cao WW. Ambipolar ferromagnetism by electrostatic doping of a manganite. Nat Commun 2018; 9:1897. [PMID: 29765044 PMCID: PMC5953920 DOI: 10.1038/s41467-018-04233-5] [Citation(s) in RCA: 39] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2017] [Accepted: 04/12/2018] [Indexed: 11/09/2022] Open
Abstract
Complex-oxide materials exhibit physical properties that involve the interplay of charge and spin degrees of freedom. However, an ambipolar oxide that is able to exhibit both electron-doped and hole-doped ferromagnetism in the same material has proved elusive. Here we report ambipolar ferromagnetism in LaMnO3, with electron-hole asymmetry of the ferromagnetic order. Starting from an undoped atomically thin LaMnO3 film, we electrostatically dope the material with electrons or holes according to the polarity of a voltage applied across an ionic liquid gate. Magnetotransport characterization reveals that an increase of either electron-doping or hole-doping induced ferromagnetic order in this antiferromagnetic compound, and leads to an insulator-to-metal transition with colossal magnetoresistance showing electron-hole asymmetry. These findings are supported by density functional theory calculations, showing that strengthening of the inter-plane ferromagnetic exchange interaction is the origin of the ambipolar ferromagnetism. The result raises the prospect of exploiting ambipolar magnetic functionality in strongly correlated electron systems.
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Affiliation(s)
- L M Zheng
- Condensed Matter Science and Technology Institute, School of Science, Harbin Institute of Technology, Harbin, 150081, China
| | - X Renshaw Wang
- School of Physical and Mathematical Sciences & School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore, 639798, Singapore.
| | - W M Lü
- Condensed Matter Science and Technology Institute, School of Science, Harbin Institute of Technology, Harbin, 150081, China.
| | - C J Li
- Department of Materials Science and Engineering, National University of Singapore, Singapore, 117575, Singapore
| | - T R Paudel
- Department of Physics and Astronomy & Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, Nebraska, 68588, USA
| | - Z Q Liu
- School of Materials Science and Engineering, Beihang University, Beijing, 100191, China
| | - Z Huang
- NUSNNI-NanoCore, National University of Singapore, Singapore, 117411, Singapore
| | - S W Zeng
- NUSNNI-NanoCore, National University of Singapore, Singapore, 117411, Singapore
| | - Kun Han
- NUSNNI-NanoCore, National University of Singapore, Singapore, 117411, Singapore
| | - Z H Chen
- Department of Materials Science and Engineering, University of California, Berkeley, Berkeley, CA, 94720, USA.,Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA.,School of Materials Science and Engineering, Harbin Institute of Technology, Shenzhen, Guangzhou, 518055, China
| | - X P Qiu
- Shanghai Key Laboratory of Special Artificial Microstructure Materials and Technology & Pohl Institute of Solid State Physics & School of Physics Science and Engineering, Tongji University, Shanghai, 200092, China
| | - M S Li
- Department of Materials Science and Engineering, National University of Singapore, Singapore, 117575, Singapore
| | - Shize Yang
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - B Yang
- Condensed Matter Science and Technology Institute, School of Science, Harbin Institute of Technology, Harbin, 150081, China
| | - Matthew F Chisholm
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - L W Martin
- Department of Materials Science and Engineering, University of California, Berkeley, Berkeley, CA, 94720, USA.,Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
| | - S J Pennycook
- Department of Materials Science and Engineering, National University of Singapore, Singapore, 117575, Singapore
| | - E Y Tsymbal
- Department of Physics and Astronomy & Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, Nebraska, 68588, USA
| | - J M D Coey
- School of Physics, Trinity College, Dublin, 2, Ireland.,Faculty of Materials Science and Engineering, Beihang University, Beijing, 100191, China
| | - W W Cao
- Condensed Matter Science and Technology Institute, School of Science, Harbin Institute of Technology, Harbin, 150081, China.,Department of Mathematics and Materials Research Institute, The Pennsylvania State University, University Park, PA, 16802, USA
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4
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Ma HJH, Scharinger S, Zeng SW, Kohlberger D, Lange M, Stöhr A, Wang XR, Venkatesan T, Kleiner R, Scott JF, Coey JMD, Koelle D. Local Electrical Imaging of Tetragonal Domains and Field-Induced Ferroelectric Twin Walls in Conducting SrTiO_{3}. Phys Rev Lett 2016; 116:257601. [PMID: 27391752 DOI: 10.1103/physrevlett.116.257601] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/05/2015] [Indexed: 06/06/2023]
Abstract
We demonstrate electrical mapping of tetragonal domains and electric field-induced twin walls in SrTiO_{3} as a function of temperature and gate bias utilizing the conducting LaAlO_{3}/SrTiO_{3} interface and low-temperature scanning electron microscopy. Conducting twin walls appear below 105 K, and new twin patterns are observed after thermal cycling through the transition or on electric field gating. The nature of the twin walls is confirmed by calculating their intersection angles for different substrate orientations. Numerous walls formed when a large side- or back-gate voltage is applied are identified as field-induced ferroelectric twin walls in the paraelectric tetragonal matrix. The walls persist after switching off the electric field and on thermal cycling below 105 K. These observations point to a new type of ferroelectric functionality in SrTiO_{3}, which could be exploited together with magnetism and superconductivity in a multifunctional context.
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Affiliation(s)
- H J Harsan Ma
- NUSNNI-Nanocore, National University of Singapore, 117411 Singapore, Singapore
- Department of Physics, National University of Singapore, 117542 Singapore, Singapore
| | - S Scharinger
- Physikalisches Institut and Center for Quantum Science (CQ) in LISA+, Universität Tübingen, Auf der Morgenstelle 14, D-72076 Tübingen, Germany
| | - S W Zeng
- NUSNNI-Nanocore, National University of Singapore, 117411 Singapore, Singapore
- Department of Physics, National University of Singapore, 117542 Singapore, Singapore
| | - D Kohlberger
- Physikalisches Institut and Center for Quantum Science (CQ) in LISA+, Universität Tübingen, Auf der Morgenstelle 14, D-72076 Tübingen, Germany
| | - M Lange
- Physikalisches Institut and Center for Quantum Science (CQ) in LISA+, Universität Tübingen, Auf der Morgenstelle 14, D-72076 Tübingen, Germany
| | - A Stöhr
- Physikalisches Institut and Center for Quantum Science (CQ) in LISA+, Universität Tübingen, Auf der Morgenstelle 14, D-72076 Tübingen, Germany
| | - X Renshaw Wang
- NUSNNI-Nanocore, National University of Singapore, 117411 Singapore, Singapore
- Department of Physics, National University of Singapore, 117542 Singapore, Singapore
| | - T Venkatesan
- NUSNNI-Nanocore, National University of Singapore, 117411 Singapore, Singapore
- Department of Physics, National University of Singapore, 117542 Singapore, Singapore
- Department of Electrical and Computer Engineering, National University of Singapore, 117576 Singapore, Singapore
| | - R Kleiner
- Physikalisches Institut and Center for Quantum Science (CQ) in LISA+, Universität Tübingen, Auf der Morgenstelle 14, D-72076 Tübingen, Germany
| | - J F Scott
- School of Chemistry and School of Physics, St. Andrews University, St. Andrews KY16 9ST, United Kingdom
| | - J M D Coey
- NUSNNI-Nanocore, National University of Singapore, 117411 Singapore, Singapore
- Department of Pure and Applied Physics, Trinity College, Dublin 2, Ireland
| | - D Koelle
- Physikalisches Institut and Center for Quantum Science (CQ) in LISA+, Universität Tübingen, Auf der Morgenstelle 14, D-72076 Tübingen, Germany
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5
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Lü WM, Saha S, Wang XR, Liu ZQ, Gopinadhan K, Annadi A, Zeng SW, Huang Z, Bao BC, Cong CX, Venkatesan M, Yu T, Coey JMD, Ariando, Venkatesan T. Long-range magnetic coupling across a polar insulating layer. Nat Commun 2016; 7:11015. [PMID: 26980456 PMCID: PMC4799368 DOI: 10.1038/ncomms11015] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2015] [Accepted: 02/11/2016] [Indexed: 11/25/2022] Open
Abstract
Magnetic interactions in solids are normally mediated by short-range exchange or weak dipole fields. Here we report a magnetic interaction that can propagate over long distances (∼10 nm) across a polar insulating oxide spacer. Evidence includes oscillations of magnetization, coercivity and field-cooled loop shift with the thickness of LaAlO3 in La0.67Sr0.33MnO3/LaAlO3/SrTiO3 heterostructures. Similar modifications of the hysteresis loop appear when two coupled films of La0.67Sr0.33MnO3 are separated by LaAlO3, or another polar insulator, but they are absent when the oxide spacer layer is nonpolar. The loop shift is attributed to strong spin–orbit coupling and Dzyaloshinskii–Moriya interaction at the interfaces. There is evidence from inelastic light scattering that the polar spacer mediates long-range transmission of orbital magnetization. This coupling mechanism is expected to apply for any conducting ferromagnetic oxide with mixed valence; in view of electron hopping frequency involved, it raises the prospect of terahertz tunability of magnetic coupling. Magnetic interactions in solids are usually short-range or else they involve itinerant electrons. Here, the authors evidence a long-range magnetic coupling mediated by orbital moments in a polar spacer layer of nonmagnetic insulating oxide, with a sign which oscillates with spacer thickness.
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Affiliation(s)
- W M Lü
- NUSNNI-Nanocore, National University of Singapore, Singapore 117411, Singapore
| | - Surajit Saha
- NUSNNI-Nanocore, National University of Singapore, Singapore 117411, Singapore.,Department of Physics, National University of Singapore, Singapore 117542, Singapore
| | - X Renshaw Wang
- NUSNNI-Nanocore, National University of Singapore, Singapore 117411, Singapore.,Department of Physics, National University of Singapore, Singapore 117542, Singapore
| | - Z Q Liu
- NUSNNI-Nanocore, National University of Singapore, Singapore 117411, Singapore.,Department of Physics, National University of Singapore, Singapore 117542, Singapore
| | - K Gopinadhan
- NUSNNI-Nanocore, National University of Singapore, Singapore 117411, Singapore
| | - A Annadi
- NUSNNI-Nanocore, National University of Singapore, Singapore 117411, Singapore.,Department of Physics, National University of Singapore, Singapore 117542, Singapore
| | - S W Zeng
- NUSNNI-Nanocore, National University of Singapore, Singapore 117411, Singapore.,Department of Physics, National University of Singapore, Singapore 117542, Singapore
| | - Z Huang
- NUSNNI-Nanocore, National University of Singapore, Singapore 117411, Singapore
| | - B C Bao
- Division of Physics and Applied Physics, School of Physical and Mathematical Science, Nanyang Technological University, Singapore 637371, Singapore
| | - C X Cong
- Division of Physics and Applied Physics, School of Physical and Mathematical Science, Nanyang Technological University, Singapore 637371, Singapore
| | - M Venkatesan
- Department of Pure and Applied Physics, Trinity College, Dublin 2, Ireland
| | - T Yu
- Division of Physics and Applied Physics, School of Physical and Mathematical Science, Nanyang Technological University, Singapore 637371, Singapore
| | - J M D Coey
- NUSNNI-Nanocore, National University of Singapore, Singapore 117411, Singapore.,Department of Pure and Applied Physics, Trinity College, Dublin 2, Ireland
| | - Ariando
- NUSNNI-Nanocore, National University of Singapore, Singapore 117411, Singapore.,Department of Physics, National University of Singapore, Singapore 117542, Singapore
| | - T Venkatesan
- NUSNNI-Nanocore, National University of Singapore, Singapore 117411, Singapore.,Department of Physics, National University of Singapore, Singapore 117542, Singapore.,Department of Electrical and Computer Engineering, National University of Singapore, Singapore 117576, Singapore
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6
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Renshaw Wang X, Sun L, Huang Z, Lü WM, Motapothula M, Annadi A, Liu ZQ, Zeng SW, Venkatesan T, Ariando. Parallel charge sheets of electron liquid and gas in La0.5Sr0.5TiO3/SrTiO3 heterostructures. Sci Rep 2015; 5:18282. [PMID: 26669575 PMCID: PMC4680910 DOI: 10.1038/srep18282] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2015] [Accepted: 09/14/2015] [Indexed: 12/05/2022] Open
Abstract
We show here a new phenomenon in La0.5Sr0.5TiO3/SrTiO3 (LSTO/STO) heterostructures; that is a coexistence of three-dimensional electron liquid (3DEL) and 2D electron gas (2DEG), separated by an intervening insulating LSTO layer. The two types of carriers were revealed through multi-channel analysis of the evolution of nonlinear Hall effect as a function of film thickness, temperature and back gate voltage. We demonstrate that the 3D electron originates from La doping in LSTO film and the 2D electron at the surface of STO is due to the polar field in the intervening insulating layer. As the film thickness is reduced below a critical thickness of 6 unit cells (uc), an abrupt metal-to-insulator transition (MIT) occurs without an intermediate semiconducting state. The properties of the LSTO layer grown on different substrates suggest that the insulating phase of the intervening layer is a result of interface strain induced by the lattice mismatch between the film and substrate. Further, by fitting the magnetoresistance (MR) curves, the 6 unit cell thick LSTO is shown to exhibit spin-orbital coupling. These observations point to new functionalities, in addition to magnetism and superconductivity in STO-based systems, which could be exploited in a multifunctional context.
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Affiliation(s)
- X Renshaw Wang
- NUSNNI-Nanocore, National University of Singapore, 117411 Singapore.,Department of Physics, National University of Singapore, 117542 Singapore.,Faculty of Science and Technology and MESA+ Institute for Nanotechnology, University of Twente, P.O. BOX 217, 7500 AE Enschede, The Netherlands
| | - L Sun
- NUSNNI-Nanocore, National University of Singapore, 117411 Singapore
| | - Z Huang
- NUSNNI-Nanocore, National University of Singapore, 117411 Singapore.,Department of Physics, National University of Singapore, 117542 Singapore
| | - W M Lü
- NUSNNI-Nanocore, National University of Singapore, 117411 Singapore.,Department of Physics, National University of Singapore, 117542 Singapore
| | - M Motapothula
- NUSNNI-Nanocore, National University of Singapore, 117411 Singapore.,Department of Physics, National University of Singapore, 117542 Singapore
| | - A Annadi
- NUSNNI-Nanocore, National University of Singapore, 117411 Singapore.,Department of Physics, National University of Singapore, 117542 Singapore
| | - Z Q Liu
- NUSNNI-Nanocore, National University of Singapore, 117411 Singapore.,Department of Physics, National University of Singapore, 117542 Singapore
| | - S W Zeng
- NUSNNI-Nanocore, National University of Singapore, 117411 Singapore.,Department of Physics, National University of Singapore, 117542 Singapore
| | - T Venkatesan
- NUSNNI-Nanocore, National University of Singapore, 117411 Singapore.,Department of Physics, National University of Singapore, 117542 Singapore.,Department of Electrical and Computer Engineering, National University of Singapore, 117576 Singapore.,National University of Singapore Graduate School for Integrative Sciences and Engineering (NGS), 28 Medical Drive, Singapore 117456, Singapore
| | - Ariando
- NUSNNI-Nanocore, National University of Singapore, 117411 Singapore.,Department of Physics, National University of Singapore, 117542 Singapore.,National University of Singapore Graduate School for Integrative Sciences and Engineering (NGS), 28 Medical Drive, Singapore 117456, Singapore
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7
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Annadi A, Zhang Q, Renshaw Wang X, Tuzla N, Gopinadhan K, Lü WM, Roy Barman A, Liu ZQ, Srivastava A, Saha S, Zhao YL, Zeng SW, Dhar S, Olsson E, Gu B, Yunoki S, Maekawa S, Hilgenkamp H, Venkatesan T, Ariando. Anisotropic two-dimensional electron gas at the LaAlO₃/SrTiO₃ (110) interface. Nat Commun 2013; 4:1838. [PMID: 23673623 PMCID: PMC3674248 DOI: 10.1038/ncomms2804] [Citation(s) in RCA: 86] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2012] [Accepted: 03/25/2013] [Indexed: 11/15/2022] Open
Abstract
The observation of a high-mobility two-dimensional electron gas between two insulating complex oxides, especially LaAlO3/SrTiO3, has enhanced the potential of oxides for electronics. The occurrence of this conductivity is believed to be driven by polarization discontinuity, leading to an electronic reconstruction. In this scenario, the crystal orientation has an important role and no conductivity would be expected, for example, for the interface between LaAlO3 and (110)-oriented SrTiO3, which should not have a polarization discontinuity. Here we report the observation of unexpected conductivity at the LaAlO3/SrTiO3 interface prepared on (110)-oriented SrTiO3, with a LaAlO3-layer thickness-dependent metal-insulator transition. Density functional theory calculation reveals that electronic reconstruction, and thus conductivity, is still possible at this (110) interface by considering the energetically favourable (110) interface structure, that is, buckled TiO2/LaO, in which the polarization discontinuity is still present. The conductivity was further found to be strongly anisotropic along the different crystallographic directions with potential for anisotropic superconductivity and magnetism, leading to possible new physics and applications. Although LaAlO3 and SrTiO3 are both insulators, when they are brought together at a (100) interface, a highly conducting two-dimensional electron gas forms between them. Annandi et al. show that this also happens at a (110) interface, counter to expectations that it should not.
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Affiliation(s)
- A Annadi
- NUSNNI-Nanocore, National University of Singapore, Singapore 117411, Singapore
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8
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Liu ZQ, Leusink DP, Wang X, Lü WM, Gopinadhan K, Annadi A, Zhao YL, Huang XH, Zeng SW, Huang Z, Srivastava A, Dhar S, Venkatesan T. Metal-insulator transition in SrTiO(3-x) thin films induced by frozen-out carriers. Phys Rev Lett 2011; 107:146802. [PMID: 22112172 DOI: 10.1103/physrevlett.107.146802] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/20/2011] [Indexed: 05/31/2023]
Abstract
We report optical, electrical and magnetotransport properties of oxygen deficient SrTiO(3) (SrTiO(3-x)) thin films fabricated by pulsed laser deposition technique. The oxygen vacancies (O(vac)) in the thin film are expected to be uniform. By comparing its electrical properties to those of bulk SrTiO(3-x), it was found that O(vac) in bulk SrTiO(3-x) is far from uniform over the whole material. The metal-insulator transition (MIT) observed in the SrTiO(3-x) film was found to be induced by the carrier freeze-out effect. The low temperature frozen state can be reexcited by Joule heating, electric and intriguingly magnetic field.
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Affiliation(s)
- Z Q Liu
- NUSNNI-Nanocore, National University of Singapore, 117542 Singapore
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