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Lee D, Chung B, Shi Y, Kim GY, Campbell N, Xue F, Song K, Choi SY, Podkaminer JP, Kim TH, Ryan PJ, Kim JW, Paudel TR, Kang JH, Spinuzzi JW, Tenne DA, Tsymbal EY, Rzchowski MS, Chen LQ, Lee J, Eom CB. Isostructural metal-insulator transition in VO2. Science 2018; 362:1037-1040. [DOI: 10.1126/science.aam9189] [Citation(s) in RCA: 111] [Impact Index Per Article: 18.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2017] [Revised: 09/28/2017] [Accepted: 10/12/2018] [Indexed: 11/02/2022]
Abstract
The metal-insulator transition in correlated materials is usually coupled to a symmetry-lowering structural phase transition. This coupling not only complicates the understanding of the basic mechanism of this phenomenon but also limits the speed and endurance of prospective electronic devices. We demonstrate an isostructural, purely electronically driven metal-insulator transition in epitaxial heterostructures of an archetypal correlated material, vanadium dioxide. A combination of thin-film synthesis, structural and electrical characterizations, and theoretical modeling reveals that an interface interaction suppresses the electronic correlations without changing the crystal structure in this otherwise correlated insulator. This interaction stabilizes a nonequilibrium metallic phase and leads to an isostructural metal-insulator transition. This discovery will provide insights into phase transitions of correlated materials and may aid the design of device functionalities.
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Affiliation(s)
- D. Lee
- Department of Materials Science and Engineering, University of Wisconsin, Madison, WI 53706, USA
| | - B. Chung
- School of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon 16419, Korea
| | - Y. Shi
- Department of Materials Science and Engineering, Pennsylvania State University, University Park, PA 16802, USA
| | - G.-Y. Kim
- Department of Materials Modeling and Characterization, Korea Institute of Materials Science, Changwon 642-831, Korea
| | - N. Campbell
- Department of Physics, University of Wisconsin, Madison, WI 53706, USA
| | - F. Xue
- Department of Materials Science and Engineering, Pennsylvania State University, University Park, PA 16802, USA
| | - K. Song
- Department of Materials Modeling and Characterization, Korea Institute of Materials Science, Changwon 642-831, Korea
| | - S.-Y. Choi
- Department of Materials Modeling and Characterization, Korea Institute of Materials Science, Changwon 642-831, Korea
| | - J. P. Podkaminer
- Department of Materials Science and Engineering, University of Wisconsin, Madison, WI 53706, USA
| | - T. H. Kim
- Department of Materials Science and Engineering, University of Wisconsin, Madison, WI 53706, USA
| | - P. J. Ryan
- Advanced Photon Source, Argonne National Laboratory, Argonne, IL 60439, USA
- School of Physical Sciences, Dublin City University, Dublin 9, Ireland
| | - J.-W. Kim
- Advanced Photon Source, Argonne National Laboratory, Argonne, IL 60439, USA
| | - T. R. Paudel
- Department of Physics and Astronomy and Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, NE 68588, USA
| | - J.-H. Kang
- Department of Materials Science and Engineering, University of Wisconsin, Madison, WI 53706, USA
| | - J. W. Spinuzzi
- Department of Physics, Boise State University, Boise, ID 83725, USA
| | - D. A. Tenne
- Department of Physics, Boise State University, Boise, ID 83725, USA
| | - E. Y. Tsymbal
- Department of Physics and Astronomy and Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, NE 68588, USA
| | - M. S. Rzchowski
- Department of Physics, University of Wisconsin, Madison, WI 53706, USA
| | - L. Q. Chen
- Department of Materials Science and Engineering, Pennsylvania State University, University Park, PA 16802, USA
| | - J. Lee
- School of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon 16419, Korea
| | - C. B. Eom
- Department of Materials Science and Engineering, University of Wisconsin, Madison, WI 53706, USA
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2
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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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3
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Lee H, Campbell N, Lee J, Asel TJ, Paudel TR, Zhou H, Lee JW, Noesges B, Seo J, Park B, Brillson LJ, Oh SH, Tsymbal EY, Rzchowski MS, Eom CB. Direct observation of a two-dimensional hole gas at oxide interfaces. Nat Mater 2018; 17:231-236. [PMID: 29403056 DOI: 10.1038/s41563-017-0002-4] [Citation(s) in RCA: 50] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/24/2017] [Accepted: 11/27/2017] [Indexed: 06/07/2023]
Abstract
The discovery of a two-dimensional electron gas (2DEG) at the LaAlO3/SrTiO3 interface 1 has resulted in the observation of many properties2-5 not present in conventional semiconductor heterostructures, and so become a focal point for device applications6-8. Its counterpart, the two-dimensional hole gas (2DHG), is expected to complement the 2DEG. However, although the 2DEG has been widely observed 9 , the 2DHG has proved elusive. Herein we demonstrate a highly mobile 2DHG in epitaxially grown SrTiO3/LaAlO3/SrTiO3 heterostructures. Using electrical transport measurements and in-line electron holography, we provide direct evidence of a 2DHG that coexists with a 2DEG at complementary heterointerfaces in the same structure. First-principles calculations, coherent Bragg rod analysis and depth-resolved cathodoluminescence spectroscopy consistently support our finding that to eliminate ionic point defects is key to realizing a 2DHG. The coexistence of a 2DEG and a 2DHG in a single oxide heterostructure provides a platform for the exciting physics of confined electron-hole systems and for developing applications.
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Affiliation(s)
- H Lee
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI, USA
| | - N Campbell
- Department of Physics, University of Wisconsin-Madison, Madison, WI, USA
| | - J Lee
- Department of Energy Science, Sungkyunkwan University (SKKU), Suwon, Korea
| | - T J Asel
- Department of Physics, The Ohio State University, Columbus, OH, USA
| | - T R Paudel
- Department of Physics and Astronomy, Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, NE, USA
| | - H Zhou
- X-Ray Science Division, Advanced Photon Source, Argonne National Laboratory, Argonne, IL, USA
| | - J W Lee
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI, USA
| | - B Noesges
- Department of Physics, The Ohio State University, Columbus, OH, USA
| | - J Seo
- Department of Energy Science, Sungkyunkwan University (SKKU), Suwon, Korea
| | - B Park
- Department of Energy Science, Sungkyunkwan University (SKKU), Suwon, Korea
- Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang, Korea
| | - L J Brillson
- Department of Physics, The Ohio State University, Columbus, OH, USA
- Department of Electrical and Computer Engineering, The Ohio State University, Columbus, OH, USA
| | - S H Oh
- Department of Energy Science, Sungkyunkwan University (SKKU), Suwon, Korea
| | - E Y Tsymbal
- Department of Physics and Astronomy, Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, NE, USA
| | - M S Rzchowski
- Department of Physics, University of Wisconsin-Madison, Madison, WI, USA
| | - C B Eom
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI, USA.
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Lee D, Lu H, Gu Y, Choi SY, Li SD, Ryu S, Paudel TR, Song K, Mikheev E, Lee S, Stemmer S, Tenne DA, Oh SH, Tsymbal EY, Wu X, Chen LQ, Gruverman A, Eom CB. Emergence of room-temperature ferroelectricity at reduced dimensions. Science 2015; 349:1314-7. [DOI: 10.1126/science.aaa6442] [Citation(s) in RCA: 210] [Impact Index Per Article: 23.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
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Wang XR, Li CJ, Lu WM, Paudel TR, Leusink DP, Hoek M, Poccia N, Vailionis A, Venkatesan T, Coey JMD, Tsymbal EY, Ariando, Hilgenkamp H. Imaging and control of ferromagnetism in LaMnO3/SrTiO3 heterostructures. Science 2015; 349:716-9. [DOI: 10.1126/science.aaa5198] [Citation(s) in RCA: 129] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
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Sharma P, Ryu S, Burton JD, Paudel TR, Bark CW, Huang Z, Tsymbal EY, Catalan G, Eom CB, Gruverman A. Mechanical Tuning of LaAlO3/SrTiO3 Interface Conductivity. Nano Lett 2015; 15:3547-3551. [PMID: 25860855 DOI: 10.1021/acs.nanolett.5b01021] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
In recent years, complex-oxide heterostructures and their interfaces have become the focus of significant research activity, primarily driven by the discovery of emerging states and functionalities that open up opportunities for the development of new oxide-based nanoelectronic devices. The highly conductive state at the interface between insulators LaAlO3 and SrTiO3 is a prime example of such emergent functionality, with potential application in high electron density transistors. In this report, we demonstrate a new paradigm for voltage-free tuning of LaAlO3/SrTiO3 (LAO/STO) interface conductivity, which involves the mechanical gating of interface conductance through stress exerted by the tip of a scanning probe microscope. The mechanical control of channel conductivity and the long retention time of the induced resistance states enable transistor functionality with zero gate voltage.
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Affiliation(s)
| | - S Ryu
- ‡Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
| | | | | | - C W Bark
- ‡Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
| | | | | | - G Catalan
- ∥ICREA-Institut Catala de Recerca i Estudis Avançats, Barcelona, Spain
- ⊥ICN2-Institut Catala de Nanociencia i Nanotecnologia, Campus de Bellaterra, Barcelona, Spain
| | - C B Eom
- ‡Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
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Bark CW, Sharma P, Wang Y, Baek SH, Lee S, Ryu S, Folkman CM, Paudel TR, Kumar A, Kalinin SV, Sokolov A, Tsymbal EY, Rzchowski MS, Gruverman A, Eom CB. Switchable induced polarization in LaAlO3/SrTiO3 heterostructures. Nano Lett 2012; 12:1765-1771. [PMID: 22400486 DOI: 10.1021/nl3001088] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Demonstration of a tunable conductivity of the LaAlO(3)/SrTiO(3) interfaces drew significant attention to the development of oxide electronic structures where electronic confinement can be reduced to the nanometer range. While the mechanisms for the conductivity modulation are quite different and include metal-insulator phase transition and surface charge writing, generally it is implied that this effect is a result of electrical modification of the LaAlO(3) surface (either due to electrochemical dissociation of surface adsorbates or free charge deposition) leading to the change in the two-dimensional electron gas (2DEG) density at the LaAlO(3)/SrTiO(3) (LAO/STO) interface. In this paper, using piezoresponse force microscopy we demonstrate a switchable electromechanical response of the LAO overlayer, which we attribute to the motion of oxygen vacancies through the LAO layer thickness. These electrically induced reversible changes in bulk stoichiometry of the LAO layer are a signature of a possible additional mechanism for nanoscale oxide 2DEG control on LAO/STO interfaces.
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Affiliation(s)
- C W Bark
- Department of Materials Science and Engineering, University of Wisconsin, Madison, Wisconsin 53706, USA
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