1
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Ding C, Dong W, Jiao X, Zhang Z, Gong G, Wei Z, Wang L, Jia JF, Xue QK. Unidirectional Charge Orders Induced by Oxygen Vacancies on SrTiO 3(001). ACS NANO 2024; 18:17786-17793. [PMID: 38935417 DOI: 10.1021/acsnano.4c03317] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/28/2024]
Abstract
The discovery of high-mobility two-dimensional electron gas and low carrier density superconductivity in multiple SrTiO3-based heterostructures has stimulated intense interest in the surface properties of SrTiO3. The recent discovery of high-Tc superconductivity in the monolayer FeSe/SrTiO3 led to the upsurge and underscored the atomic precision probe of the surface structure. By performing atomically resolved cryogenic scanning tunneling microscopy/spectroscopy characterization on dual-TiO2-δ-terminated SrTiO3(001) surfaces with (√13 × √13), c(4 × 2), mixed (2 × 1), and (2 × 2) reconstructions, we disclosed universally broken rotational symmetry and contrasting bias- and temperature-dependent electronic states for apical and equatorial oxygen sites. With the sequentially evolved surface reconstructions and simultaneously increasing equatorial oxygen vacancies, the surface anisotropy reduces and the work function lowers. Intriguingly, unidirectional stripe orders appear on the c(4 × 2) surface, whereas local (4 × 4) order emerges and eventually forms long-range unidirectional c(4 × 4) charge order on the (2 × 2) surface. This work reveals robust unidirectional charge orders induced by oxygen vacancies due to strong and delicate electronic-lattice interaction under broken rotational symmetry, providing insights into understanding the complex behaviors in perovskite oxide-based heterostructures.
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Affiliation(s)
- Cui Ding
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
- Quantum Science Center of Guangdong-HongKong-Macao Greater Bay Area, Shenzhen 518045, China
| | - Wenfeng Dong
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
| | - Xiaotong Jiao
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
| | - Zhiyu Zhang
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
| | - Guanming Gong
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
| | - Zhongxu Wei
- Department of Physics, Southern University of Science and Technology, Shenzhen 518055, China
| | - Lili Wang
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
- Frontier Science Center for Quantum Information, Beijing 100084, China
| | - Jin-Feng Jia
- Quantum Science Center of Guangdong-HongKong-Macao Greater Bay Area, Shenzhen 518045, China
- Department of Physics, Southern University of Science and Technology, Shenzhen 518055, China
- Department of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Qi-Kun Xue
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
- Quantum Science Center of Guangdong-HongKong-Macao Greater Bay Area, Shenzhen 518045, China
- Department of Physics, Southern University of Science and Technology, Shenzhen 518055, China
- Frontier Science Center for Quantum Information, Beijing 100084, China
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2
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He R, Xu H, Yang P, Chang K, Wang H, Zhong Z. Ferroelastic Twin-Wall-Mediated Ferroelectriclike Behavior and Bulk Photovoltaic Effect in SrTiO_{3}. PHYSICAL REVIEW LETTERS 2024; 132:176801. [PMID: 38728736 DOI: 10.1103/physrevlett.132.176801] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/16/2023] [Revised: 02/08/2024] [Accepted: 03/29/2024] [Indexed: 05/12/2024]
Abstract
Ferroelastic twin walls in nonpolar materials can give rise to a spontaneous polarization due to symmetry breaking. Nevertheless, the bistable polarity of twin walls and its reversal have not yet been demonstrated. Here, we report that the polarity of SrTiO_{3} twin walls can be switched by an ultralow strain gradient. Using first-principles-based machine-learning potential, we demonstrate that the twin walls can be deterministically rotated and realigned in specific directions under the strain gradient, which breaks the inversion symmetry of a sequence of walls and leads to a macroscopic polarization. The system can maintain polarity even after the constraint is removed. As a result, the polarization of twin walls can exhibit a ferroelectriclike hysteresis loop upon cyclic bending, namely flexoferroelectricity. Finally, we propose a scheme to experimentally detect the polarity of the twin wall by measuring the bulk photovoltaic responses. Our findings suggest a twin-wall-mediated flexoferroelectricity in SrTiO_{3}, which could be potentially exploited as functional elements in nanoelectronic devices design.
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Affiliation(s)
- Ri He
- Key Laboratory of Magnetic Materials Devices & Zhejiang Province Key Laboratory of Magnetic Materials and Application Technology, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201, China
| | - Haowei Xu
- Department of Nuclear Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Peijun Yang
- Key Laboratory of Magnetic Materials Devices & Zhejiang Province Key Laboratory of Magnetic Materials and Application Technology, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201, China
| | - Kai Chang
- Center for Quantum Matter, Zhejiang University, Hangzhou 310058, China
- School of Physics, Zhejiang University, Hangzhou 310058, China
| | - Hua Wang
- Center for Quantum Matter, Zhejiang University, Hangzhou 310058, China
- ZJU-Hangzhou Global Scientific and Technological Innovation Center, Hangzhou 311215, China
- School of Physics, Zhejiang University, Hangzhou 310058, China
| | - Zhicheng Zhong
- Key Laboratory of Magnetic Materials Devices & Zhejiang Province Key Laboratory of Magnetic Materials and Application Technology, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201, China
- Suzhou Institute for Advanced Research, University of Science and Technology of China, Suzhou 215123, China
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3
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Nethwewala A, Lee H, Li J, Briggeman M, Pai YY, Eom K, Eom CB, Irvin P, Levy J. Electron pairing and nematicity in LaAlO 3/SrTiO 3 nanostructures. Nat Commun 2023; 14:7657. [PMID: 37996464 PMCID: PMC10667274 DOI: 10.1038/s41467-023-43539-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2023] [Accepted: 11/13/2023] [Indexed: 11/25/2023] Open
Abstract
Strongly correlated electronic systems exhibit a wealth of unconventional behavior stemming from strong electron-electron interactions. The LaAlO3/SrTiO3 (LAO/STO) heterostructure supports rich and varied low-temperature transport characteristics including low-density superconductivity, and electron pairing without superconductivity for which the microscopic origins is still not understood. LAO/STO also exhibits inexplicable signatures of electronic nematicity via nonlinear and anomalous Hall effects. Nanoscale control over the conductivity of the LAO/STO interface enables mesoscopic experiments that can probe these effects and address their microscopic origins. Here we report a direct correlation between electron pairing without superconductivity, anomalous Hall effect and electronic nematicity in quasi-1D ballistic nanoscale LAO/STO Hall crosses. The characteristic magnetic field at which the Hall coefficient changes directly coincides with the depairing of non-superconducting pairs showing a strong correlation between the two distinct phenomena. Angle-dependent Hall measurements further reveal an onset of electronic nematicity that again coincides with the electron pairing transition, unveiling a rotational symmetry breaking due to the transition from paired to unpaired phases at the interface. The results presented here highlights the influence of preformed electron pairs on the transport properties of LAO/STO and provide evidence of the elusive pairing "glue" that gives rise to electron pairing in SrTiO3-based systems.
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Affiliation(s)
- Aditi Nethwewala
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA, 15260, USA
- Pittsburgh Quantum Institute, Pittsburgh, PA, 15260, USA
| | - Hyungwoo Lee
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - Jianan Li
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA, 15260, USA
- Pittsburgh Quantum Institute, Pittsburgh, PA, 15260, USA
| | - Megan Briggeman
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA, 15260, USA
- Pittsburgh Quantum Institute, Pittsburgh, PA, 15260, USA
| | - Yun-Yi Pai
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA, 15260, USA
- Pittsburgh Quantum Institute, Pittsburgh, PA, 15260, USA
| | - Kitae Eom
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - Chang-Beom Eom
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - Patrick Irvin
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA, 15260, USA
- Pittsburgh Quantum Institute, Pittsburgh, PA, 15260, USA
| | - Jeremy Levy
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA, 15260, USA.
- Pittsburgh Quantum Institute, Pittsburgh, PA, 15260, USA.
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA, 15260, USA.
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4
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Zhao J, Ying Y, Zeng H, Zhao K, Li G, Li W. Nanoscale Thermal Strain Engineering-Driven Ferroelastic Domain Evolution in CH 3NH 3PbI 3 Perovskites. ACS APPLIED MATERIALS & INTERFACES 2023; 15:12502-12510. [PMID: 36848597 DOI: 10.1021/acsami.2c19592] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
A local thermal strain engineering approach via an ac-heated thermal probe was incorporated into methylammonium lead triiodide (MAPbI3) crystals and acts as a driving force for ferroic twin domain dynamics, local ion migration, and property tailoring. Periodically, striped ferroic twin domains and their dynamic evolutions were successfully induced by local thermal strain and high-resolution thermal imaging, giving decisive evidence of the ferroelastic nature in MAPbI3 perovskites at room temperature. Local thermal ionic imaging and chemical mappings demonstrate that domain contrasts are from local methylammonium (MA+) redistribution into the stripes of chemical segregation in response to the local thermal strain fields. The present results reveal an inherent coupling among local thermal strains, ferroelastic twin domains, local chemical-ion segregations, and physical properties and offer a potential path to improve the functionality of metal halide perovskite-based solar cells.
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Affiliation(s)
- Jiaqi Zhao
- School of Materials Science and Engineering, University of Shanghai for Science and Technology, Shanghai 200093, China
- CAS Key Laboratory of Inorganic Functional Materials and Devices, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 201899, China
- Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yuxin Ying
- CAS Key Laboratory of Inorganic Functional Materials and Devices, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 201899, China
- Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Huarong Zeng
- CAS Key Laboratory of Inorganic Functional Materials and Devices, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 201899, China
- Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Kunyu Zhao
- CAS Key Laboratory of Inorganic Functional Materials and Devices, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 201899, China
- Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Guorong Li
- CAS Key Laboratory of Inorganic Functional Materials and Devices, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 201899, China
- Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Wei Li
- School of Materials Science and Engineering, University of Shanghai for Science and Technology, Shanghai 200093, China
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5
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Christensen DV. Perspectives on oxide heterostructures - the curious case of γ-Al 2O 3/SrTiO 3. NANOSCALE 2023; 15:3704-3712. [PMID: 36723154 DOI: 10.1039/d2nr07172j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
The heterostructure formed by depositing nanoscale thin films of spinel γ-Al2O3 on perovskite SrTiO3 exhibits a range of exciting properties including room temperature epitaxial growth, high electron mobility, strain-tunable magnetic order, and a symmetry-related reordering of the conduction bands. In comparison to the benchmark LaAlO3/SrTiO3 heterostructure, the γ-Al2O3/SrTiO3 heterostructure has been more sparsely investigated, which leaves plenty of room for scientific and technological discoveries. In this perspective article, I describe the key findings of the γ-Al2O3/SrTiO3 heterostructure and propose five directions for future research: (1) an exploration of novel phenomena emerging when relaxing the conventional epitaxial constraint of matching crystal structures across the interface, (2) a dynamic switching of a strong polarization through nanoscale electromigration of aluminum vacancies, (3) autonomous and forced enhancement of the electron mobility via oxygen vacancy diffusion, (4) writing and erasing of magnetic and conducting nanolines using ferroelastic domain walls, and (5) a multiferroic state formed by combining ferroelectricity, ferromagnetism, and ferroelasticity. The proposed research directions may shed light on both fundamental aspects of the heterostructure and pave the way for applications within green energy devices and nanoelectronics.
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6
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Kumar C, Birkbeck J, Sulpizio JA, Perello D, Taniguchi T, Watanabe K, Reuven O, Scaffidi T, Stern A, Geim AK, Ilani S. Imaging hydrodynamic electrons flowing without Landauer-Sharvin resistance. Nature 2022; 609:276-281. [PMID: 36071191 DOI: 10.1038/s41586-022-05002-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2021] [Accepted: 06/21/2022] [Indexed: 11/09/2022]
Abstract
Electrical resistance usually originates from lattice imperfections. However, even a perfect lattice has a fundamental resistance limit, given by the Landauer1 conductance caused by a finite number of propagating electron modes. This resistance, shown by Sharvin2 to appear at the contacts of electronic devices, sets the ultimate conduction limit of non-interacting electrons. Recent years have seen growing evidence of hydrodynamic electronic phenomena3-18, prompting recent theories19,20 to ask whether an electronic fluid can radically break the fundamental Landauer-Sharvin limit. Here, we use single-electron-transistor imaging of electronic flow in high-mobility graphene Corbino disk devices to answer this question. First, by imaging ballistic flows at liquid-helium temperatures, we observe a Landauer-Sharvin resistance that does not appear at the contacts but is instead distributed throughout the bulk. This underpins the phase-space origin of this resistance-as emerging from spatial gradients in the number of conduction modes. At elevated temperatures, by identifying and accounting for electron-phonon scattering, we show the details of the purely hydrodynamic flow. Strikingly, we find that electron hydrodynamics eliminates the bulk Landauer-Sharvin resistance. Finally, by imaging spiralling magneto-hydrodynamic Corbino flows, we show the key emergent length scale predicted by hydrodynamic theories-the Gurzhi length. These observations demonstrate that electronic fluids can dramatically transcend the fundamental limitations of ballistic electrons, with important implications for fundamental science and future technologies.
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Affiliation(s)
- C Kumar
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot, Israel
| | - J Birkbeck
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot, Israel
| | - J A Sulpizio
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot, Israel
| | - D Perello
- School of Physics & Astronomy, University of Manchester, Manchester, UK.,National Graphene Institute, University of Manchester, Manchester, UK
| | - T Taniguchi
- National Institute for Materials Science, Tsukuba, Japan
| | - K Watanabe
- National Institute for Materials Science, Tsukuba, Japan
| | - O Reuven
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot, Israel
| | - T Scaffidi
- Department of Physics, University of Toronto, Toronto, ON, Canada.,Department of Physics and Astronomy, University of California, Irvine, CA, USA
| | - Ady Stern
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot, Israel
| | - A K Geim
- School of Physics & Astronomy, University of Manchester, Manchester, UK.,National Graphene Institute, University of Manchester, Manchester, UK
| | - S Ilani
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot, Israel.
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7
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Yu M, Liu C, Yang D, Yan X, Du Q, Fong DD, Bhattacharya A, Irvin P, Levy J. Nanoscale Control of the Metal-Insulator Transition at LaAlO 3/KTaO 3 Interfaces. NANO LETTERS 2022; 22:6062-6068. [PMID: 35862274 DOI: 10.1021/acs.nanolett.2c00673] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Recent reports of superconductivity at KTaO3 (KTO) (110) and (111) interfaces have sparked intense interest due to the relatively high critical temperature as well as other properties that distinguish this system from the more extensively studied SrTiO3 (STO)-based heterostructures. Here, we report the reconfigurable creation of conducting structures at intrinsically insulating LaAlO3/KTO(110) and (111) interfaces. Devices are created using two distinct methods previously developed for STO-based heterostructures: (1) conductive atomic-force microscopy lithography and (2) ultralow-voltage electron-beam lithography. At low temperatures, KTO(110)-based devices show superconductivity that is tunable by an applied back gate. A one-dimensional nanowire device shows single-electron-transistor (SET) behavior. A KTO(111)-based device is metallic but does not become superconducting. These reconfigurable methods of creating nanoscale devices in KTO-based heterostructures offer new avenues for investigating mechanisms of superconductivity as well as development of quantum devices that incorporate strong spin-orbit interactions, superconducting behavior, and nanoscale dimensions.
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Affiliation(s)
- Muqing Yu
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
- Pittsburgh Quantum Institute, Pittsburgh, Pennsylvania 15260, United States
| | - Changjiang Liu
- Materials Science Division, Argonne National Laboratory, Lemont, Illinois 60439, United States
| | - Dengyu Yang
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
- Pittsburgh Quantum Institute, Pittsburgh, Pennsylvania 15260, United States
| | - Xi Yan
- Materials Science Division, Argonne National Laboratory, Lemont, Illinois 60439, United States
| | - Qianheng Du
- Materials Science Division, Argonne National Laboratory, Lemont, Illinois 60439, United States
| | - Dillon D Fong
- Materials Science Division, Argonne National Laboratory, Lemont, Illinois 60439, United States
| | - Anand Bhattacharya
- Materials Science Division, Argonne National Laboratory, Lemont, Illinois 60439, United States
| | - Patrick Irvin
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
- Pittsburgh Quantum Institute, Pittsburgh, Pennsylvania 15260, United States
| | - Jeremy Levy
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
- Pittsburgh Quantum Institute, Pittsburgh, Pennsylvania 15260, United States
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8
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Erlandsen R, Dahm RT, Trier F, Scuderi M, Di Gennaro E, Sambri A, Reffeldt Kirchert CK, Pryds N, Granozio FM, Jespersen TS. A Two-Dimensional Superconducting Electron Gas in Freestanding LaAlO 3/SrTiO 3 Micromembranes. NANO LETTERS 2022; 22:4758-4764. [PMID: 35679577 DOI: 10.1021/acs.nanolett.2c00992] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Freestanding oxide membranes constitute an intriguing material platform for new functionalities and allow integration of oxide electronics with technologically important platforms such as silicon. Sambri et al. recently reported a method to fabricate freestanding LaAlO3/SrTiO3 (LAO/STO) membranes by spalling of strained heterostructures. Here, we first develop a scheme for the high-yield fabrication of membrane devices on silicon. Second, we show that the membranes exhibit metallic conductivity and a superconducting phase below ∼200 mK. Using anisotropic magnetotransport we extract the superconducting phase coherence length ξ ≈ 36-80 nm and establish an upper bound on the thickness of the superconducting electron gas d ≈ 17-33 nm, thus confirming its two-dimensional character. Finally, we show that the critical current can be modulated using a silicon-based backgate. The ability to form superconducting nanostructures of LAO/STO membranes, with electronic properties similar to those of the bulk counterpart, opens opportunities for integrating oxide nanoelectronics with silicon-based architectures.
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Affiliation(s)
- Ricci Erlandsen
- Department of Energy Conversion and Storage, Technical University of Denmark, Fysikvej, Building 310, 2800 Kgs. Lyngby, Denmark
| | - Rasmus Tindal Dahm
- Department of Energy Conversion and Storage, Technical University of Denmark, Fysikvej, Building 310, 2800 Kgs. Lyngby, Denmark
| | - Felix Trier
- Department of Energy Conversion and Storage, Technical University of Denmark, Fysikvej, Building 310, 2800 Kgs. Lyngby, Denmark
| | - Mario Scuderi
- Institute for Microelectronics and Microsystems (CNR-IMM), Strada VIII n.5 Zona Industriale, I-95121 Catania, Italy
| | - Emiliano Di Gennaro
- Dipartimento di Fisica "Ettore Pancini", Università degli Studi di Napoli Federico II, Complesso Universitario di Monte S. Angelo, Via Cinthia, I-80126 Napoli, Italy
| | - Alessia Sambri
- CNR-SPIN, Complesso Universitario di Monte Sant'Angelo, Via Cinthia, I-80126 Napoli, Italy
| | | | - Nini Pryds
- Department of Energy Conversion and Storage, Technical University of Denmark, Fysikvej, Building 310, 2800 Kgs. Lyngby, Denmark
| | - Fabio Miletto Granozio
- CNR-SPIN, Complesso Universitario di Monte Sant'Angelo, Via Cinthia, I-80126 Napoli, Italy
| | - Thomas Sand Jespersen
- Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark
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9
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Yue J, Ayino Y, Truttmann TK, Gastiasoro MN, Persky E, Khanukov A, Lee D, Thoutam LR, Kalisky B, Fernandes RM, Pribiag VS, Jalan B. Anomalous transport in high-mobility superconducting SrTiO 3 thin films. SCIENCE ADVANCES 2022; 8:eabl5668. [PMID: 35613270 PMCID: PMC9132441 DOI: 10.1126/sciadv.abl5668] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/21/2021] [Accepted: 04/08/2022] [Indexed: 06/15/2023]
Abstract
The study of subtle effects on transport in semiconductors requires high-quality epitaxial structures with low defect density. Using hybrid molecular beam epitaxy (MBE), SrTiO3 films with a low-temperature mobility exceeding 42,000 cm2 V-1 s-1 at a low carrier density of 3 × 1017 cm-3 were achieved. A sudden and sharp decrease in residual resistivity accompanied by an enhancement in the superconducting transition temperature were observed across the second Lifshitz transition where the third band becomes occupied, revealing dominant intraband scattering. These films further revealed an anomalous behavior in the Hall carrier density as a consequence of the antiferrodistortive (AFD) transition and the temperature dependence of the Hall scattering factor. Using hybrid MBE growth, phenomenological modeling, temperature-dependent transport measurements, and scanning superconducting quantum interference device imaging, we provide critical insights into the important role of inter- versus intraband scattering and of AFD domain walls on normal-state and superconducting properties of SrTiO3.
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Affiliation(s)
- Jin Yue
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, MN 55455, USA
| | - Yilikal Ayino
- School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455, USA
| | - Tristan K. Truttmann
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, MN 55455, USA
| | - Maria N. Gastiasoro
- School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455, USA
| | - Eylon Persky
- Department of Physics and Institute of Nanotechnology and Advanced Materials, Bar-Ilan University, Ramat Gan 5290002, Israel
| | - Alex Khanukov
- Department of Physics and Institute of Nanotechnology and Advanced Materials, Bar-Ilan University, Ramat Gan 5290002, Israel
| | - Dooyong Lee
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, MN 55455, USA
| | - Laxman R. Thoutam
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, MN 55455, USA
| | - Beena Kalisky
- Department of Physics and Institute of Nanotechnology and Advanced Materials, Bar-Ilan University, Ramat Gan 5290002, Israel
| | - Rafael M. Fernandes
- School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455, USA
| | - Vlad S. Pribiag
- School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455, USA
| | - Bharat Jalan
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, MN 55455, USA
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10
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Mikheev E, Rosen IT, Goldhaber-Gordon D. Quantized critical supercurrent in SrTiO 3-based quantum point contacts. SCIENCE ADVANCES 2021; 7:eabi6520. [PMID: 34597141 PMCID: PMC10938545 DOI: 10.1126/sciadv.abi6520] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/05/2021] [Accepted: 08/11/2021] [Indexed: 06/13/2023]
Abstract
Superconductivity in SrTiO3 occurs at remarkably low carrier densities and therefore, unlike conventional superconductors, can be controlled by electrostatic gates. Here, we demonstrate nanoscale weak links connecting superconducting leads, all within a single material, SrTiO3. Ionic liquid gating accumulates carriers in the leads, and local electrostatic gates are tuned to open the weak link. These devices behave as superconducting quantum point contacts with a quantized critical supercurrent. This is a milestone toward establishing SrTiO3 as a single-material platform for mesoscopic superconducting transport experiments that also intrinsically contains the necessary ingredients to engineer topological superconductivity.
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Affiliation(s)
- Evgeny Mikheev
- Department of Physics, Stanford University, Stanford, CA 94305, USA
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, CA 94025, USA
| | - Ilan T. Rosen
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, CA 94025, USA
- Department of Applied Physics, Stanford University, Stanford, CA 94305, USA
| | - David Goldhaber-Gordon
- Department of Physics, Stanford University, Stanford, CA 94305, USA
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, CA 94025, USA
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11
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Krantz PW, Chandrasekhar V. Observation of Zero-Field Transverse Resistance in AlO_{x}/SrTiO_{3} Interface Devices. PHYSICAL REVIEW LETTERS 2021; 127:036801. [PMID: 34328768 DOI: 10.1103/physrevlett.127.036801] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/07/2020] [Accepted: 06/10/2021] [Indexed: 06/13/2023]
Abstract
Domain walls in AlO_{x}/SrTiO_{3} (AlO_{x}/STO) interface devices at low temperatures give a rise to a new signature in the electrical transport of two-dimensional carrier gases formed at the surfaces or interfaces of STO-based heterostructures: a finite transverse resistance observed in Hall bars in zero external magnetic field. This transverse resistance depends on the local domain wall configuration and hence changes with temperature, gate voltage, thermal cycling, and position along the sample and can even change sign as a function of these parameters. The transverse resistance is observed below ≃70 K but grows and changes significantly below ≃40 K, the temperature at which the domain walls become increasingly polar. Surprisingly, the transverse resistance is much larger in (111) oriented heterostructures in comparison to (001) oriented heterostructures. Measurements of the capacitance between the conducting interface and an electrode applied to the substrate, which reflect the dielectric constant of the STO, indicate that this difference may be related to the greater variation of the temperature-dependent dielectric constant with electric field when the electric field is applied in the [111] direction. The finite transverse resistance can be explained inhomogeneous current flow due to the preferential transport of current along domain walls that are askew to the nominal direction of the injected current.
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Affiliation(s)
- P W Krantz
- Department of Physics, Northwestern University, Evanston, Illinois 60208, USA
| | - V Chandrasekhar
- Department of Physics, Northwestern University, Evanston, Illinois 60208, USA
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12
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Rose MA, Barnett J, Wendland D, Hensling FVE, Boergers JM, Moors M, Dittmann R, Taubner T, Gunkel F. Local inhomogeneities resolved by scanning probe techniques and their impact on local 2DEG formation in oxide heterostructures. NANOSCALE ADVANCES 2021; 3:4145-4155. [PMID: 36132831 PMCID: PMC9419657 DOI: 10.1039/d1na00190f] [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: 03/12/2021] [Accepted: 06/02/2021] [Indexed: 06/16/2023]
Abstract
Lateral inhomogeneities in the formation of two-dimensional electron gases (2DEG) directly influence their electronic properties. Understanding their origin is an important factor for fundamental interpretations, as well as high quality devices. Here, we studied the local formation of the buried 2DEG at LaAlO3/SrTiO3 (LAO/STO) interfaces grown on STO (100) single crystals with partial TiO2 termination, utilizing in situ conductive atomic force microscopy (c-AFM) and scattering-type scanning near-field optical microscopy (s-SNOM). Using substrates with different degrees of chemical surface termination, we can link the resulting interface chemistry to an inhomogeneous 2DEG formation. In conductivity maps recorded by c-AFM, a significant lack of conductivity is observed at topographic features, indicative of a local SrO/AlO2 interface stacking order, while significant local conductivity can be probed in regions showing TiO2/LaO interface stacking order. These results could be corroborated by s-SNOM, showing a similar contrast distribution in the optical signal which can be linked to the local electronic properties of the material. The results are further complemented by low-temperature conductivity measurements, which show an increasing residual resistance at 5 K with increasing portion of insulating SrO-terminated areas. Therefore, we can correlate the macroscopic electrical behavior of our samples to their nanoscopic structure. Using proper parameters, 2DEG mapping can be carried out without any visible alteration of sample properties, proving c-AFM and s-SNOM to be viable and destruction-free techniques for the identification of local 2DEG formation. Furthermore, applying c-AFM and s-SNOM in this manner opens the exciting prospect to link macroscopic low-temperature transport to its nanoscopic origin.
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Affiliation(s)
- M-A Rose
- Institute of Electronic Materials (IWE II), RWTH Aachen University Aachen Germany
- Peter Gruenberg Institute, JARA-FIT, Forschungszentrum Juelich GmbH Juelich Germany
| | - J Barnett
- I. Institute of Physics (IA), RWTH Aachen University Aachen Germany
| | - D Wendland
- I. Institute of Physics (IA), RWTH Aachen University Aachen Germany
| | - F V E Hensling
- Peter Gruenberg Institute, JARA-FIT, Forschungszentrum Juelich GmbH Juelich Germany
| | - J M Boergers
- Peter Gruenberg Institute, JARA-FIT, Forschungszentrum Juelich GmbH Juelich Germany
| | - M Moors
- Peter Gruenberg Institute, JARA-FIT, Forschungszentrum Juelich GmbH Juelich Germany
| | - R Dittmann
- Peter Gruenberg Institute, JARA-FIT, Forschungszentrum Juelich GmbH Juelich Germany
| | - T Taubner
- I. Institute of Physics (IA), RWTH Aachen University Aachen Germany
| | - F Gunkel
- Institute of Electronic Materials (IWE II), RWTH Aachen University Aachen Germany
- Peter Gruenberg Institute, JARA-FIT, Forschungszentrum Juelich GmbH Juelich Germany
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13
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Non-universal current flow near the metal-insulator transition in an oxide interface. Nat Commun 2021; 12:3311. [PMID: 34083533 PMCID: PMC8175561 DOI: 10.1038/s41467-021-23393-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2021] [Accepted: 04/21/2021] [Indexed: 11/12/2022] Open
Abstract
In systems near phase transitions, macroscopic properties often follow algebraic scaling laws, determined by the dimensionality and the underlying symmetries of the system. The emergence of such universal scaling implies that microscopic details are irrelevant. Here, we locally investigate the scaling properties of the metal-insulator transition at the LaAlO3/SrTiO3 interface. We show that, by changing the dimensionality and the symmetries of the electronic system, coupling between structural and electronic properties prevents the universal behavior near the transition. By imaging the current flow in the system, we reveal that structural domain boundaries modify the filamentary flow close to the transition point, preventing a fractal with the expected universal dimension from forming. Macroscopic properties usually follow algebraic scaling laws near phase transitions. Here, the authors investigate the scaling properties of the metal‐insulator transition at the LaAlO3/SrTiO3 interface, finding that coupling between structural and electronic properties prevents the universal behavior.
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14
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Chen S, Yuan S, Hou Z, Tang Y, Zhang J, Wang T, Li K, Zhao W, Liu X, Chen L, Martin LW, Chen Z. Recent Progress on Topological Structures in Ferroic Thin Films and Heterostructures. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2021; 33:e2000857. [PMID: 32815214 DOI: 10.1002/adma.202000857] [Citation(s) in RCA: 27] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/06/2020] [Revised: 04/17/2020] [Indexed: 06/11/2023]
Abstract
Topological spin/polarization structures in ferroic materials continue to draw great attention as a result of their fascinating physical behaviors and promising applications in the field of high-density nonvolatile memories as well as future energy-efficient nanoelectronic and spintronic devices. Such developments have been made, in part, based on recent advances in theoretical calculations, the synthesis of high-quality thin films, and the characterization of their emergent phenomena and exotic phases. Herein, progress over the last decade in the study of topological structures in ferroic thin films and heterostructures is explored, including the observation of topological structures and control of their structures and emergent physical phenomena through epitaxial strain, layer thickness, electric, magnetic fields, etc. First, the evolution of topological spin structures (e.g., magnetic skyrmions) and associated functionalities (e.g., topological Hall effect) in magnetic thin films and heterostructures is discussed. Then, the exotic polar topologies (e.g., domain walls, closure domains, polar vortices, bubble domains, and polar skyrmions) and their emergent physical properties in ferroelectric oxide films and heterostructures are explored. Finally, a brief overview and prospectus of how the field may evolve in the coming years is provided.
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Affiliation(s)
- Shanquan Chen
- School of Materials Science and Engineering, Harbin Institute of Technology, Shenzhen, 518055, China
| | - Shuai Yuan
- School of Materials Science and Engineering, Harbin Institute of Technology, Shenzhen, 518055, China
| | - Zhipeng Hou
- Guangdong Provincial Key Laboratory of Optical Information Materials and Technology & Institute for Advanced Materials, South China Academy of Advanced Optoelectronics, South China Normal University, Guangzhou, 510006, P. R. China
- National Center for International Research on Green Optoelectronics, South China Normal University, Guangzhou, 510006, P. R. China
| | - Yunlong Tang
- Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Wenhua Road 72, Shenyang, 110016, China
| | - Jinping Zhang
- School of Materials Science and Engineering, Harbin Institute of Technology, Shenzhen, 518055, China
| | - Tao Wang
- School of Materials Science and Engineering, Harbin Institute of Technology, Shenzhen, 518055, China
| | - Kang Li
- Flexible Printed Electronics Technology Center, Harbin Institute of Technology, Shenzhen, 518055, China
| | - Weiwei Zhao
- School of Materials Science and Engineering, Harbin Institute of Technology, Shenzhen, 518055, China
- Flexible Printed Electronics Technology Center, Harbin Institute of Technology, Shenzhen, 518055, China
| | - Xingjun Liu
- School of Materials Science and Engineering, Harbin Institute of Technology, Shenzhen, 518055, China
| | - Lang Chen
- Department of Physics, Southern University of Science and Technology, Shenzhen, 518055, China
| | - Lane W Martin
- Department of Materials Science and Engineering, University of California, Berkeley, CA, 94720, USA
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
| | - Zuhuang Chen
- School of Materials Science and Engineering, Harbin Institute of Technology, Shenzhen, 518055, China
- Flexible Printed Electronics Technology Center, Harbin Institute of Technology, Shenzhen, 518055, China
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15
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Chen S, Chen X, Duijnstee EA, Sanyal B, Banerjee T. Unveiling Temperature-Induced Structural Domains and Movement of Oxygen Vacancies in SrTiO 3 with Graphene. ACS APPLIED MATERIALS & INTERFACES 2020; 12:52915-52921. [PMID: 33175485 PMCID: PMC7705893 DOI: 10.1021/acsami.0c15458] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/27/2020] [Accepted: 11/03/2020] [Indexed: 06/11/2023]
Abstract
Heterointerfaces coupling complex oxides exhibit coexisting functional properties such as magnetism, superconductivity, and ferroelectricity, often absent in their individual constituent. SrTiO3 (STO), a canonical band insulator, is an active constituent of such heterointerfaces. Temperature-, strain-, or mechanical stress-induced ferroelastic transition leads to the formation of narrow domains and domain walls in STO. Such ferroelastic domain walls have been studied using imaging or transport techniques and, often, the findings are influenced by the choice and interaction of the electrodes with STO. In this work, we use graphene as a unique platform to unveil the movement of oxygen vacancies and ferroelastic domain walls near the STO surface by studying the temperature and gate bias dependence of charge transport in graphene. By sweeping the back gate voltage, we observe antihysteresis in graphene typically observed in conventional ferroelectric oxides. Interestingly, we find features in antihysteresis that are related to the movement of domain walls and of oxygen vacancies in STO. We ascertain this by analyzing the time dependence of the graphene square resistance at different temperatures and gate bias. Density functional calculations estimate the surface polarization and formation energies of layer-dependent oxygen vacancies in STO. This corroborates quantitatively with the activation energies determined from the temperature dependence of the graphene square resistance. Introduction of a hexagonal boron nitride (hBN) layer, of varying thicknesses, between graphene and STO leads to a gradual disappearance of the observed features, implying the influence of the domain walls onto the potential landscape in graphene.
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Affiliation(s)
- Si Chen
- Zernike
Institute for Advanced Materials, University
of Groningen, 9747 AG Groningen, The Netherlands
| | - Xin Chen
- Department
of Physics and Astronomy, Uppsala University, P.O. Box 516, 751 20 Uppsala, Sweden
| | - Elisabeth A. Duijnstee
- Zernike
Institute for Advanced Materials, University
of Groningen, 9747 AG Groningen, The Netherlands
| | - Biplab Sanyal
- Department
of Physics and Astronomy, Uppsala University, P.O. Box 516, 751 20 Uppsala, Sweden
| | - Tamalika Banerjee
- Zernike
Institute for Advanced Materials, University
of Groningen, 9747 AG Groningen, The Netherlands
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16
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Lebedev N, Stehno M, Rana A, Gauquelin N, Verbeeck J, Brinkman A, Aarts J. Inhomogeneous superconductivity and quasilinear magnetoresistance at amorphous LaTiO 3/SrTiO 3 interfaces. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2020; 33:055001. [PMID: 33169729 DOI: 10.1088/1361-648x/abc102] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
We have studied the transport properties of LaTiO3/SrTiO3 (LTO/STO) heterostructures. In spite of 2D growth observed in reflection high energy electron diffraction, transmission electron microscopy images revealed that the samples tend to amorphize. Still, we observe that the structures are conducting, and some of them exhibit high conductance and/or superconductivity. We established that conductivity arises mainly on the STO side of the interface, and shows all the signs of the two-dimensional electron gas usually observed at interfaces between STO and LTO or LaAlO3, including the presence of two electron bands and tunability with a gate voltage. Analysis of magnetoresistance (MR) and superconductivity indicates the presence of spatial fluctuations of the electronic properties in our samples. That can explain the observed quasilinear out-of-plane MR, as well as various features of the in-plane MR and the observed superconductivity.
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Affiliation(s)
- N Lebedev
- Huygens-Kamerlingh Onnes Laboratory, Leiden University, P.O. Box 9504, 2300 RA Leiden, The Netherlands
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17
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Rodenbücher C, Bittkau K, Bihlmayer G, Wrana D, Gensch T, Korte C, Krok F, Szot K. Mapping the conducting channels formed along extended defects in SrTiO 3 by means of scanning near-field optical microscopy. Sci Rep 2020; 10:17763. [PMID: 33082447 PMCID: PMC7576817 DOI: 10.1038/s41598-020-74645-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2020] [Accepted: 09/30/2020] [Indexed: 12/23/2022] Open
Abstract
Mixed ionic-electronic-conducting perovskites such as SrTiO3 are promising materials to be employed in efficient energy conversion or information processing. These materials exhibit a self-doping effect related to the formation of oxygen vacancies and electronic charge carriers upon reduction. It has been found that dislocations play a prominent role in this self-doping process, serving as easy reduction sites, which result in the formation of conducting filaments along the dislocations. While this effect has been investigated in detail with theoretical calculations and direct observations using local-conductivity atomic force microscopy, the present work highlights the optical properties of dislocations in SrTiO3 single crystals. Using the change in optical absorption upon reduction as an indicator, two well-defined arrangements of dislocations, namely a bicrystal boundary and a slip band induced by mechanical deformation, are investigated by means of scanning near-field optical microscopy. In both cases, the regions with enhanced dislocation density can be clearly identified as regions with higher optical absorption. Assisted by ab initio calculations, confirming that the agglomeration of oxygen vacancies significantly change the local dielectric constants of the material, the results provide direct evidence that reduced dislocations can be classified as alien matter embedded in the SrTiO3 matrix.
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Affiliation(s)
- Christian Rodenbücher
- Institute of Energy and Climate Research (IEK-14), Forschungszentrum Jülich GmbH, 52425, Jülich, Germany.
| | - Karsten Bittkau
- Institute of Energy and Climate Research (IEK-5), Forschungszentrum Jülich GmbH, 52425, Jülich, Germany
| | - Gustav Bihlmayer
- Peter Grünberg Institut (PGI-1) and JARA-FIT, Forschungszentrum Jülich GmbH, 52425, Jülich, Germany
| | - Dominik Wrana
- Marian Smoluchowski Institute of Physics, Jagiellonian University, 30-348, Krakow, Poland
| | - Thomas Gensch
- Institute of Biological Information Processing (IBI-1), Forschungszentrum Jülich GmbH, 52425, Jülich, Germany
| | - Carsten Korte
- Institute of Energy and Climate Research (IEK-14), Forschungszentrum Jülich GmbH, 52425, Jülich, Germany
| | - Franciszek Krok
- Marian Smoluchowski Institute of Physics, Jagiellonian University, 30-348, Krakow, Poland
| | - Kristof Szot
- Institute of Physics, University of Silesia, 41-500, Chorzów, Poland
- aixACCT Systems GmbH, 52068, Aachen, Germany
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18
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Tuvia G, Frenkel Y, Rout PK, Silber I, Kalisky B, Dagan Y. Ferroelectric Exchange Bias Affects Interfacial Electronic States. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2020; 32:e2000216. [PMID: 32510654 DOI: 10.1002/adma.202000216] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/10/2020] [Revised: 04/20/2020] [Indexed: 06/11/2023]
Abstract
In polar oxide interfaces phenomena such as superconductivity, magnetism, 1D conductivity, and quantum Hall states can emerge at the polar discontinuity. Combining controllable ferroelectricity at such interfaces can affect the superconducting properties and sheds light on the mutual effects between the polar oxide and the ferroelectric oxide. Here, the interface between the polar oxide LaAlO3 and the ferroelectric Ca-doped SrTiO3 is studied by means of electrical transport combined with local imaging of the current flow with the use of scanning a superconducting quantum interference device (SQUID). Anomalous behavior of the interface resistivity is observed at low temperatures. The scanning SQUID maps of the current flow suggest that this behavior originates from an intrinsic bias induced by the polar LaAlO3 layer. Such intrinsic bias combined with ferroelectricity can constrain the possible structural domain tiling near the interface. The use of this intrinsic bias is recommended as a method of controlling and tuning the initial state of ferroelectric materials by the design of the polar structure. The hysteretic dependence of the normal and the superconducting state properties on gate voltage can be utilized in multifaceted controllable memory devices.
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Affiliation(s)
- Gal Tuvia
- Raymond and Beverly Sackler School of Physics, Tel Aviv University, Tel Aviv, 6997801, Israel
| | - Yiftach Frenkel
- Department of Physics and Institute of Nanotechnology and Advanced Materials, Bar-Ilan University, Ramat-Gan, 5290002, Israel
| | - Prasanna K Rout
- Raymond and Beverly Sackler School of Physics, Tel Aviv University, Tel Aviv, 6997801, Israel
| | - Itai Silber
- Raymond and Beverly Sackler School of Physics, Tel Aviv University, Tel Aviv, 6997801, Israel
| | - Beena Kalisky
- Department of Physics and Institute of Nanotechnology and Advanced Materials, Bar-Ilan University, Ramat-Gan, 5290002, Israel
| | - Yoram Dagan
- Raymond and Beverly Sackler School of Physics, Tel Aviv University, Tel Aviv, 6997801, Israel
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19
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Zondiner U, Rozen A, Rodan-Legrain D, Cao Y, Queiroz R, Taniguchi T, Watanabe K, Oreg Y, von Oppen F, Stern A, Berg E, Jarillo-Herrero P, Ilani S. Cascade of phase transitions and Dirac revivals in magic-angle graphene. Nature 2020; 582:203-208. [PMID: 32528091 DOI: 10.1038/s41586-020-2373-y] [Citation(s) in RCA: 119] [Impact Index Per Article: 29.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2019] [Accepted: 04/23/2020] [Indexed: 11/09/2022]
Abstract
Twisted bilayer graphene near the magic angle1-4 exhibits rich electron-correlation physics, displaying insulating3-6, magnetic7,8 and superconducting phases4-6. The electronic bands of this system were predicted1,2 to narrow markedly9,10 near the magic angle, leading to a variety of possible symmetry-breaking ground states11-17. Here, using measurements of the local electronic compressibility, we show that these correlated phases originate from a high-energy state with an unusual sequence of band population. As carriers are added to the system, the four electronic 'flavours', which correspond to the spin and valley degrees of freedom, are not filled equally. Rather, they are populated through a sequence of sharp phase transitions, which appear as strong asymmetric jumps of the electronic compressibility near integer fillings of the moiré lattice. At each transition, a single spin/valley flavour takes all the carriers from its partially filled peers, 'resetting' them to the vicinity of the charge neutrality point. As a result, the Dirac-like character observed near charge neutrality reappears after each integer filling. Measurement of the in-plane magnetic field dependence of the chemical potential near filling factor one reveals a large spontaneous magnetization, further substantiating this picture of a cascade of symmetry breaking. The sequence of phase transitions and Dirac revivals is observed at temperatures well above the onset of the superconducting and correlated insulating states. This indicates that the state that we report here, with its strongly broken electronic flavour symmetry and revived Dirac-like electronic character, is important in the physics of magic-angle graphene, forming the parent state out of which the more fragile superconducting and correlated insulating ground states emerge.
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Affiliation(s)
- U Zondiner
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot, Israel
| | - A Rozen
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot, Israel
| | - D Rodan-Legrain
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Y Cao
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - R Queiroz
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot, Israel
| | - T Taniguchi
- National Institute for Materials Science, Tsukuba, Japan
| | - K Watanabe
- National Institute for Materials Science, Tsukuba, Japan
| | - Y Oreg
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot, Israel
| | - F von Oppen
- Dahlem Center for Complex Quantum Systems and Fachbereich Physik, Freie Universität Berlin, Berlin, Germany
| | - Ady Stern
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot, Israel
| | - E Berg
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot, Israel
| | - P Jarillo-Herrero
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA, USA.
| | - S Ilani
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot, Israel.
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20
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Khivrich I, Ilani S. Atomic-like charge qubit in a carbon nanotube enabling electric and magnetic field nano-sensing. Nat Commun 2020; 11:2299. [PMID: 32385257 PMCID: PMC7210973 DOI: 10.1038/s41467-020-16001-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2019] [Accepted: 04/07/2020] [Indexed: 11/09/2022] Open
Abstract
Quantum sensing techniques have been successful in pushing the sensitivity limits in numerous fields, and hold promise for scanning probes that study nano-scale devices and materials. However, forming a nano-scale qubit that is simple and robust enough to be placed on a scanning tip, and sensitive enough to detect various physical observables, is still a great challenge. Here, we demonstrate, in a carbon nanotube, an implementation of a charge qubit that achieves these requirements. Our qubit’s basis states are formed from the natural electronic wavefunctions in a single quantum dot. Different magnetic moments and charge distributions of these wavefunctions make it sensitive to magnetic and electric fields, while difference in their electrical transport allows a simple transport-based readout mechanism. We demonstrate electric field sensitivity better than that of a single electron transistor, and DC magnetic field sensitivity comparable to that of NV centers. Due to its simplicity, this qubit can be fabricated using conventional techniques. These features make this atomic-like qubit a powerful tool, enabling a variety of imaging experiments. Among the recent developments in quantum technologies, the use of qubits for quantum sensing has led to significant improvements in resolution and sensitivity at the nanoscale. Here, the authors present a carbon nanotube charge qubit that can act as a highly sensitive scanning probe of electric and magnetic fields.
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Affiliation(s)
- I Khivrich
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot, 76100, Israel
| | - S Ilani
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot, 76100, Israel.
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21
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van Thiel TC, Fowlie J, Autieri C, Manca N, Šiškins M, Afanasiev D, Gariglio S, Caviglia AD. Coupling Lattice Instabilities Across the Interface in Ultrathin Oxide Heterostructures. ACS MATERIALS LETTERS 2020; 2:389-394. [PMID: 32478332 PMCID: PMC7254603 DOI: 10.1021/acsmaterialslett.9b00540] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/19/2019] [Accepted: 03/09/2020] [Indexed: 06/11/2023]
Abstract
Oxide heterointerfaces constitute a rich platform for realizing novel functionalities in condensed matter. A key aspect is the strong link between structural and electronic properties, which can be modified by interfacing materials with distinct lattice symmetries. Here, we determine the effect of the cubic-tetragonal distortion of SrTiO3 on the electronic properties of thin films of SrIrO3, a topological crystalline metal hosting a delicate interplay between spin-orbit coupling and electronic correlations. We demonstrate that below the transition temperature at 105 K, SrIrO3 orthorhombic domains couple directly to tetragonal domains in SrTiO3. This forces the in-phase rotational axis to lie in-plane and creates a binary domain structure in the SrIrO3 film. The close proximity to the metal-insulator transition in ultrathin SrIrO3 causes the individual domains to have strongly anisotropic transport properties, driven by a reduction of bandwidth along the in-phase axis. The strong structure-property relationships in perovskites make these compounds particularly suitable for static and dynamic coupling at interfaces, providing a promising route towards realizing novel functionalities in oxide heterostructures.
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Affiliation(s)
- Thierry C. van Thiel
- Kavli
Institute of Nanoscience, Delft University
of Technology, Lorentzweg 1, 2628 CJ Delft, Netherlands
| | - Jennifer Fowlie
- Department
of Quantum Matter Physics, University of
Geneva, 24 Quai Ernest-Ansermet, 1211 Genève 4, Switzerland
| | - Carmine Autieri
- International
Research Centre MagTop, Institute of Physics, Polish Academy of Sciences, Aleja Lotników 32/46, PL-02668 Warsaw, Poland
- Consiglio
Nazionale delle Ricerche, Istituto Superconduttori,
Materiali Innovativi e Dispositivi (CNR-SPIN), c/o Università G. D’Annunzio, I-66100 Chieti, Italy
| | - Nicola Manca
- Kavli
Institute of Nanoscience, Delft University
of Technology, Lorentzweg 1, 2628 CJ Delft, Netherlands
| | - Makars Šiškins
- Kavli
Institute of Nanoscience, Delft University
of Technology, Lorentzweg 1, 2628 CJ Delft, Netherlands
| | - Dmytro Afanasiev
- Kavli
Institute of Nanoscience, Delft University
of Technology, Lorentzweg 1, 2628 CJ Delft, Netherlands
| | - Stefano Gariglio
- Department
of Quantum Matter Physics, University of
Geneva, 24 Quai Ernest-Ansermet, 1211 Genève 4, Switzerland
| | - Andrea D. Caviglia
- Kavli
Institute of Nanoscience, Delft University
of Technology, Lorentzweg 1, 2628 CJ Delft, Netherlands
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22
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23
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Luo W, Boselli M, Poumirol JM, Ardizzone I, Teyssier J, van der Marel D, Gariglio S, Triscone JM, Kuzmenko AB. High sensitivity variable-temperature infrared nanoscopy of conducting oxide interfaces. Nat Commun 2019; 10:2774. [PMID: 31235858 PMCID: PMC6591405 DOI: 10.1038/s41467-019-10672-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2019] [Accepted: 05/21/2019] [Indexed: 11/09/2022] Open
Abstract
Probing the local transport properties of two-dimensional electron systems (2DES) confined at buried interfaces requires a non-invasive technique with a high spatial resolution operating in a broad temperature range. In this paper, we investigate the scattering-type scanning near field optical microscopy as a tool for studying the conducting LaAlO3/SrTiO3 interface from room temperature down to 6 K. We show that the near-field optical signal, in particular its phase component, is highly sensitive to the transport properties of the electron system present at the interface. Our modeling reveals that such sensitivity originates from the interaction of the AFM tip with coupled plasmon-phonon modes with a small penetration depth. The model allows us to quantitatively correlate changes in the optical signal with the variation of the 2DES transport properties induced by cooling and by electrostatic gating. To probe the spatial resolution of the technique, we image conducting nano-channels written in insulating heterostructures with a voltage-biased tip of an atomic force microscope.
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Affiliation(s)
- Weiwei Luo
- Department of Quantum Matter Physics, University of Geneva, Quai Ernest-Ansermet 24, 1211, Geneva, Switzerland
| | - Margherita Boselli
- Department of Quantum Matter Physics, University of Geneva, Quai Ernest-Ansermet 24, 1211, Geneva, Switzerland
| | - Jean-Marie Poumirol
- Department of Quantum Matter Physics, University of Geneva, Quai Ernest-Ansermet 24, 1211, Geneva, Switzerland
| | - Ivan Ardizzone
- Department of Quantum Matter Physics, University of Geneva, Quai Ernest-Ansermet 24, 1211, Geneva, Switzerland
| | - Jérémie Teyssier
- Department of Quantum Matter Physics, University of Geneva, Quai Ernest-Ansermet 24, 1211, Geneva, Switzerland
| | - Dirk van der Marel
- Department of Quantum Matter Physics, University of Geneva, Quai Ernest-Ansermet 24, 1211, Geneva, Switzerland
| | - Stefano Gariglio
- Department of Quantum Matter Physics, University of Geneva, Quai Ernest-Ansermet 24, 1211, Geneva, Switzerland
| | - Jean-Marc Triscone
- Department of Quantum Matter Physics, University of Geneva, Quai Ernest-Ansermet 24, 1211, Geneva, Switzerland
| | - Alexey B Kuzmenko
- Department of Quantum Matter Physics, University of Geneva, Quai Ernest-Ansermet 24, 1211, Geneva, Switzerland.
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24
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Ella L, Rozen A, Birkbeck J, Ben-Shalom M, Perello D, Zultak J, Taniguchi T, Watanabe K, Geim AK, Ilani S, Sulpizio JA. Simultaneous voltage and current density imaging of flowing electrons in two dimensions. NATURE NANOTECHNOLOGY 2019; 14:480-487. [PMID: 30858521 DOI: 10.1038/s41565-019-0398-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/14/2018] [Accepted: 01/31/2019] [Indexed: 06/09/2023]
Abstract
A variety of physical phenomena associated with nanoscale electron transport often results in non-trivial spatial voltage and current patterns, particularly in nonlocal transport regimes. While numerous techniques have been devised to image electron flows, the need remains for a nanoscale probe capable of simultaneously imaging current and voltage distributions with high sensitivity and minimal invasiveness, in a magnetic field, across a broad range of temperatures and beneath an insulating surface. Here we present a technique for spatially mapping electron flows based on a nanotube single-electron transistor, which achieves high sensitivity for both voltage and current imaging. In a series of experiments using high-mobility graphene devices, we demonstrate the ability of our technique to visualize local aspects of intrinsically nonlocal transport, as in ballistic flows, which are not easily resolvable via existing methods. This technique should aid in understanding the physics of two-dimensional electronic devices and enable new classes of experiments that image electron flow through buried nanostructures in the quantum and interaction-dominated regimes.
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Affiliation(s)
- Lior Ella
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot, Israel
| | - Asaf Rozen
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot, Israel
| | - John Birkbeck
- School of Physics and Astronomy, University of Manchester, Manchester, UK
- National Graphene Institute, University of Manchester, Manchester, UK
| | - Moshe Ben-Shalom
- School of Physics and Astronomy, University of Manchester, Manchester, UK
- National Graphene Institute, University of Manchester, Manchester, UK
- School of Physics and Astronomy, Tel Aviv University, Tel Aviv, Israel
| | - David Perello
- School of Physics and Astronomy, University of Manchester, Manchester, UK
- National Graphene Institute, University of Manchester, Manchester, UK
| | - Johanna Zultak
- School of Physics and Astronomy, University of Manchester, Manchester, UK
- National Graphene Institute, University of Manchester, Manchester, UK
| | | | - Kenji Watanabe
- National Institute for Materials Science, Tsukuba, Japan
| | - Andre K Geim
- School of Physics and Astronomy, University of Manchester, Manchester, UK
- National Graphene Institute, University of Manchester, Manchester, UK
| | - Shahal Ilani
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot, Israel
| | - Joseph A Sulpizio
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot, Israel.
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25
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Dunnett K, Zhu JX, Spaldin NA, Juričić V, Balatsky AV. Dynamic Multiferroicity of a Ferroelectric Quantum Critical Point. PHYSICAL REVIEW LETTERS 2019; 122:057208. [PMID: 30822032 DOI: 10.1103/physrevlett.122.057208] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/17/2018] [Indexed: 06/09/2023]
Abstract
Quantum matter hosts a large variety of phases, some coexisting, some competing; when two or more orders occur together, they are often entangled and cannot be separated. Dynamical multiferroicity, where fluctuations of electric dipoles lead to magnetization, is an example where the two orders are impossible to disentangle. Here we demonstrate an elevated magnetic response of a ferroelectric near the ferroelectric quantum critical point (FE QCP), since magnetic fluctuations are entangled with ferroelectric fluctuations. We thus suggest that any ferroelectric quantum critical point is an inherent multiferroic quantum critical point. We calculate the magnetic susceptibility near the FE QCP and find a region with enhanced magnetic signatures near the FE QCP and controlled by the tuning parameter of the ferroelectric phase. The effect is small but observable-we propose quantum paraelectric strontium titanate as a candidate material where the magnitude of the induced magnetic moments can be ∼5×10^{-7} μ_{B} per unit cell near the FE QCP.
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Affiliation(s)
- K Dunnett
- Nordita, KTH Royal Institute of Technology and Stockholm University, Roslagstullsbacken 23, SE-106 91 Stockholm, Sweden
| | - J-X Zhu
- T-4 and CINT, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - N A Spaldin
- Materials Theory, ETH Zurich, Wolfgang-Pauli-Strasse 27, CH-8093 Zürich, Switzerland
| | - V Juričić
- Nordita, KTH Royal Institute of Technology and Stockholm University, Roslagstullsbacken 23, SE-106 91 Stockholm, Sweden
| | - A V Balatsky
- Nordita, KTH Royal Institute of Technology and Stockholm University, Roslagstullsbacken 23, SE-106 91 Stockholm, Sweden
- Department of Physics, University of Connecticut, Storrs, Connecticut 06269, USA
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26
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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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27
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Pesquera D, Carpenter MA, Salje EKH. Glasslike Dynamics of Polar Domain Walls in Cryogenic SrTiO_{3}. PHYSICAL REVIEW LETTERS 2018; 121:235701. [PMID: 30576178 DOI: 10.1103/physrevlett.121.235701] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/27/2018] [Indexed: 06/09/2023]
Abstract
Polar and highly mobile domain walls in SrTiO_{3} move under electric and elastic fields. Two vastly different timescales dominate their dynamical behavior. The previously observed fast changes lead to anomalies near 40 K where the elastic moduli soften and the polarity of the walls becomes strong. Keeping the sample under isothermal conditions leads to a new and unexpected phenomenon: The softening vanishes over timescales of days while the piezoelectricity of the sample remains unchanged. The hardening follows glass dynamics below an onset at T^{*}≈40 K. The timescale of the hardening is strongly temperature dependent and can be followed experimentally down to 34 K when the relaxation is not completed within two days. The relaxation time of a stretched exponential decay increases exponentially with the decreasing temperature. This relaxation process follows similar dynamics after zero-field cooling and after applying or removing an electric field. The sluggish behavior is attributed to collective interactions of domain patterns following overdamped glass dynamics rather than ballistic dynamics.
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Affiliation(s)
- David Pesquera
- Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EQ, United Kingdom
| | - Michael A Carpenter
- Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EQ, United Kingdom
| | - Ekhard K H Salje
- Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EQ, United Kingdom
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28
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Huang Z, Renshaw Wang X, Rusydi A, Chen J, Yang H, Venkatesan T. Interface Engineering and Emergent Phenomena in Oxide Heterostructures. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2018; 30:e1802439. [PMID: 30133012 DOI: 10.1002/adma.201802439] [Citation(s) in RCA: 43] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/16/2018] [Revised: 07/06/2018] [Indexed: 06/08/2023]
Abstract
Complex oxide interfaces have mesmerized the scientific community in the last decade due to the possibility of creating tunable novel multifunctionalities, which are possible owing to the strong interaction among charge, spin, orbital, and structural degrees of freedom. Artificial interfacial modifications, which include defects, formal polarization, structural symmetry breaking, and interlayer interaction, have led to novel properties in various complex oxide heterostructures. These emergent phenomena not only serve as a platform for investigating strong electronic correlations in low-dimensional systems but also provide potentials for exploring next-generation electronic devices with high functionality. Herein, some recently developed strategies in engineering functional oxide interfaces and their emergent properties are reviewed.
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Affiliation(s)
- Zhen Huang
- NUSNNI-NanoCore, National University of Singapore, 5A Engineering Drive 1, Singapore, 117411, Singapore
| | - Xiao Renshaw Wang
- NUSNNI-NanoCore, National University of Singapore, 5A Engineering Drive 1, Singapore, 117411, Singapore
| | - Andrivo Rusydi
- NUSNNI-NanoCore, National University of Singapore, 5A Engineering Drive 1, Singapore, 117411, Singapore
| | - Jingsheng Chen
- NUSNNI-NanoCore, National University of Singapore, 5A Engineering Drive 1, Singapore, 117411, Singapore
| | - Hyunsoo Yang
- NUSNNI-NanoCore, National University of Singapore, 5A Engineering Drive 1, Singapore, 117411, Singapore
| | - Thirumalai Venkatesan
- NUSNNI-NanoCore, National University of Singapore, 5A Engineering Drive 1, Singapore, 117411, Singapore
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29
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Chen L, Li J, Tang Y, Pai YY, Chen Y, Pryds N, Irvin P, Levy J. Extreme Reconfigurable Nanoelectronics at the CaZrO 3 /SrTiO 3 Interface. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2018; 30:e1801794. [PMID: 29962024 DOI: 10.1002/adma.201801794] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/20/2018] [Revised: 05/10/2018] [Indexed: 06/08/2023]
Abstract
Complex oxide heterostructures have fascinating emergent properties that originate from the properties of the bulk constituents as well as from dimensional confinement. The conductive behavior of the polar/nonpolar LaAlO3 /SrTiO3 interface can be reversibly switched using conductive atomic force microscopy (c-AFM) lithography, enabling a wide range of devices and physics to be explored. Here, extreme nanoscale control over the CaZrO3 /SrTiO3 (CZO/STO) interface, which is formed from two materials that are both nonpolar, is reported. Nanowires with measured widths as narrow as 1.2 nm are realized at the CZO/STO interface at room temperature by c-AFM lithography. These ultrathin nanostructures have spatial dimensions at room temperature that are comparable to single-walled carbon nanotubes, and hold great promise for alternative oxide-based nanoelectronics, as well as offer new opportunities to investigate the electronic structure of the complex oxide interfaces. The cryogenic properties of devices constructed from quasi-1D channels, tunnel barriers, and planar gates exhibit gate-tunable superconductivity, quantum oscillations, electron pairing outside of the superconducting regime, and quasi-ballistic transport. This newly demonstrated ability to control the metal-insulator transition at nonpolar oxide interface greatly expands the class of materials whose behavior can be patterned and reconfigured at extreme nanoscale dimensions.
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Affiliation(s)
- Lu Chen
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA, 15260, USA
- Pittsburgh Quantum Institute, Pittsburgh, PA, 15260, USA
| | - Jianan Li
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA, 15260, USA
- Pittsburgh Quantum Institute, Pittsburgh, PA, 15260, USA
| | - Yuhe Tang
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA, 15260, USA
- Pittsburgh Quantum Institute, Pittsburgh, PA, 15260, USA
| | - Yun-Yi Pai
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA, 15260, USA
- Pittsburgh Quantum Institute, Pittsburgh, PA, 15260, USA
| | - Yunzhong Chen
- Department of Energy Conversion and Storage, Technical University of Denmark, Risø Campus, Roskilde, 4000, Denmark
| | - Nini Pryds
- Department of Energy Conversion and Storage, Technical University of Denmark, Risø Campus, Roskilde, 4000, Denmark
| | - Patrick Irvin
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA, 15260, USA
- Pittsburgh Quantum Institute, Pittsburgh, PA, 15260, USA
| | - Jeremy Levy
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA, 15260, USA
- Pittsburgh Quantum Institute, Pittsburgh, PA, 15260, USA
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30
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Jnawali G, Lee H, Lee JW, Huang M, Hsu JF, Bi F, Zhou R, Cheng G, D'Urso B, Irvin P, Eom CB, Levy J. Graphene-Complex-Oxide Nanoscale Device Concepts. ACS NANO 2018; 12:6128-6136. [PMID: 29750506 DOI: 10.1021/acsnano.8b02457] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
The integration of graphene with complex-oxide heterostructures such as LaAlO3/SrTiO3 offers the opportunity to combine the multifunctional properties of an oxide interface with the exceptional electronic properties of graphene. The ability to control interface conduction through graphene and understanding how it affects the intrinsic properties of an oxide interface are critical to the technological development of multifunctional devices. Here we demonstrate several device archetypes in which electron transport at an oxide interface is modulated using a patterned graphene top-gate. Nanoscale devices are fabricated at the oxide interface by conductive atomic force microscope (c-AFM) lithography, and transport measurements are performed as a function of the graphene gate voltage. Experiments are performed with devices written adjacent to or directly underneath the graphene gate. Distinct capabilities of this approach include the ability to create highly flexible device configurations, the ability to modulate carrier density at the oxide interface, and the ability to control electron transport up to the single-electron tunneling regime, while maintaining intrinsic transport properties of the oxide interface. Our results facilitate the design of a variety of nanoscale devices that combine excellent transport properties of these two proximal two-dimensional electron systems.
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Affiliation(s)
- Giriraj Jnawali
- Department of Physics and Astronomy , University of Pittsburgh , Pittsburgh 15260 , United States
- Pittsburgh Quantum Institute , Pittsburgh , Pennsylvania 15260 , United States
| | - Hyungwoo Lee
- Department of Materials Science and Engineering , University of Wisconsin-Madison , Madison , Wisconsin 53706 , United States
| | - Jung-Woo Lee
- Department of Materials Science and Engineering , University of Wisconsin-Madison , Madison , Wisconsin 53706 , United States
| | - Mengchen Huang
- Department of Physics and Astronomy , University of Pittsburgh , Pittsburgh 15260 , United States
- Pittsburgh Quantum Institute , Pittsburgh , Pennsylvania 15260 , United States
| | - Jen-Feng Hsu
- Department of Physics and Astronomy , University of Pittsburgh , Pittsburgh 15260 , United States
- Pittsburgh Quantum Institute , Pittsburgh , Pennsylvania 15260 , United States
| | - Feng Bi
- Department of Physics and Astronomy , University of Pittsburgh , Pittsburgh 15260 , United States
- Pittsburgh Quantum Institute , Pittsburgh , Pennsylvania 15260 , United States
| | - Rongpu Zhou
- Department of Physics and Astronomy , University of Pittsburgh , Pittsburgh 15260 , United States
- Pittsburgh Quantum Institute , Pittsburgh , Pennsylvania 15260 , United States
| | - Guanglei Cheng
- Department of Physics and Astronomy , University of Pittsburgh , Pittsburgh 15260 , United States
- Pittsburgh Quantum Institute , Pittsburgh , Pennsylvania 15260 , United States
- CAS Key Laboratory of Microscale Magnetic Resonance and Department of Modern Physics , University of Science and Technology of China , Hefei 230026 , China
| | - Brian D'Urso
- Department of Physics and Astronomy , University of Pittsburgh , Pittsburgh 15260 , United States
- Pittsburgh Quantum Institute , Pittsburgh , Pennsylvania 15260 , United States
| | - Patrick Irvin
- Department of Physics and Astronomy , University of Pittsburgh , Pittsburgh 15260 , United States
- Pittsburgh Quantum Institute , Pittsburgh , Pennsylvania 15260 , United States
| | - Chang-Beom Eom
- Department of Materials Science and Engineering , University of Wisconsin-Madison , Madison , Wisconsin 53706 , United States
| | - Jeremy Levy
- Department of Physics and Astronomy , University of Pittsburgh , Pittsburgh 15260 , United States
- Pittsburgh Quantum Institute , Pittsburgh , Pennsylvania 15260 , United States
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31
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Thierschmann H, Mulazimoglu E, Manca N, Goswami S, Klapwijk TM, Caviglia AD. Transport regimes of a split gate superconducting quantum point contact in the two-dimensional LaAlO 3/SrTiO 3 superfluid. Nat Commun 2018; 9:2276. [PMID: 29892080 PMCID: PMC5995834 DOI: 10.1038/s41467-018-04657-z] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2017] [Accepted: 05/14/2018] [Indexed: 11/08/2022] Open
Abstract
One of the hallmark experiments of quantum transport is the observation of the quantized resistance in a point contact in GaAs/AlGaAs heterostructures. Being formed with split gate technology, these structures represent in an ideal manner equilibrium reservoirs which are connected only through a few electron mode channel. It has been a long standing goal to achieve similar experimental conditions also in superconductors. Here we demonstrate the formation of a superconducting quantum point contact (SQPC) with split gate technology in a two-dimensional superconductor, utilizing the unique gate tunability of the superfluid at the LaAlO3/SrTiO3 interface. When the constriction is tuned through the action of metallic split gates we identify three regimes of transport: First, SQPC for which the supercurrent is carried only by a few quantum transport channels. Second, superconducting island strongly coupled to the equilibrium reservoirs. Third, charge island with a discrete spectrum weakly coupled to the reservoirs.
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Affiliation(s)
- Holger Thierschmann
- Kavli Institute of Nanoscience, Faculty of Applied Sciences, Delft University of Technology, Lorentzweg 1, 2628 CJ, Delft, The Netherlands.
| | - Emre Mulazimoglu
- Kavli Institute of Nanoscience, Faculty of Applied Sciences, Delft University of Technology, Lorentzweg 1, 2628 CJ, Delft, The Netherlands
| | - Nicola Manca
- Kavli Institute of Nanoscience, Faculty of Applied Sciences, Delft University of Technology, Lorentzweg 1, 2628 CJ, Delft, The Netherlands
| | - Srijit Goswami
- Kavli Institute of Nanoscience, Faculty of Applied Sciences, Delft University of Technology, Lorentzweg 1, 2628 CJ, Delft, The Netherlands
- QuTech, Delft University of Technology, Lorentzweg 1, 2628 CJ, Delft, The Netherlands
| | - Teun M Klapwijk
- Kavli Institute of Nanoscience, Faculty of Applied Sciences, Delft University of Technology, Lorentzweg 1, 2628 CJ, Delft, The Netherlands
- Physics Department, Moscow State University of Education, Moscow, 119991, Russia
| | - Andrea D Caviglia
- Kavli Institute of Nanoscience, Faculty of Applied Sciences, Delft University of Technology, Lorentzweg 1, 2628 CJ, Delft, The Netherlands.
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32
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Casals B, Schiaffino A, Casiraghi A, Hämäläinen SJ, López González D, van Dijken S, Stengel M, Herranz G. Low-Temperature Dielectric Anisotropy Driven by an Antiferroelectric Mode in SrTiO_{3}. PHYSICAL REVIEW LETTERS 2018; 120:217601. [PMID: 29883130 DOI: 10.1103/physrevlett.120.217601] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/21/2017] [Revised: 01/09/2018] [Indexed: 06/08/2023]
Abstract
Strontium titanate (SrTiO_{3}) is the quintessential material for oxide electronics. One of its hallmark features is the transition, driven by antiferrodistortive (AFD) lattice modes, from a cubic to a ferroelastic low-temperature phase. Here we investigate the evolution of the ferroelastic twin walls upon application of an electric field. Remarkably, we find that the dielectric anisotropy of tetragonal SrTiO_{3}, rather than the intrinsic domain wall polarity, is the main driving force for the motion of the twins. Based on a combined first-principles and Landau-theory analysis, we show that such anisotropy is dominated by a trilinear coupling between the polarization, the AFD lattice tilts, and a previously overlooked antiferroelectric (AFE) mode. We identify the latter AFE phonon with the so-called "R mode" at ∼440 cm^{-1}, which was previously detected in IR experiments, but whose microscopic nature was unknown.
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Affiliation(s)
- Blai Casals
- Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Campus UAB, 08193 Bellaterra, Catalonia, Spain
| | - Andrea Schiaffino
- Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Campus UAB, 08193 Bellaterra, Catalonia, Spain
| | - Arianna Casiraghi
- NanoSpin, Department of Applied Physics, Aalto University School of Science, P.O. Box 15100, FI-00076 Aalto, Finland
| | - Sampo J Hämäläinen
- NanoSpin, Department of Applied Physics, Aalto University School of Science, P.O. Box 15100, FI-00076 Aalto, Finland
| | - Diego López González
- NanoSpin, Department of Applied Physics, Aalto University School of Science, P.O. Box 15100, FI-00076 Aalto, Finland
| | - Sebastiaan van Dijken
- NanoSpin, Department of Applied Physics, Aalto University School of Science, P.O. Box 15100, FI-00076 Aalto, Finland
| | - Massimiliano Stengel
- Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Campus UAB, 08193 Bellaterra, Catalonia, Spain
- ICREA-Institució Catalana de Recerca i Estudis Avançats, Passeig Lluís Companys, 23, 08010 Barcelona, Catalonia, Spain
| | - Gervasi Herranz
- Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Campus UAB, 08193 Bellaterra, Catalonia, Spain
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33
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Pai YY, Lee H, Lee JW, Annadi A, Cheng G, Lu S, Tomczyk M, Huang M, Eom CB, Irvin P, Levy J. One-Dimensional Nature of Superconductivity at the LaAlO_{3}/SrTiO_{3} Interface. PHYSICAL REVIEW LETTERS 2018; 120:147001. [PMID: 29694119 DOI: 10.1103/physrevlett.120.147001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/18/2017] [Indexed: 06/08/2023]
Abstract
We examine superconductivity in LaAlO_{3}/SrTiO_{3} channels with widths that transition from the 1D to the 2D regime. The superconducting critical current is independent of the channel width and increases approximately linearly with the number of parallel channels. Signatures of electron pairing outside of the superconducting regime are also found to be independent of the channel width. Collectively, these results indicate that superconductivity exists at the boundary of these channels and is absent within the interior region of the channels. The intrinsic 1D nature of superconductivity at the LaAlO_{3}/SrTiO_{3} interface imposes strong physical constraints on possible electron pairing mechanisms.
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Affiliation(s)
- Yun-Yi Pai
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA
- Pittsburgh Quantum Institute, Pittsburgh, Pennsylvania 15260, USA
| | - Hyungwoo Lee
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - Jung-Woo Lee
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - Anil Annadi
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA
- Pittsburgh Quantum Institute, Pittsburgh, Pennsylvania 15260, USA
| | - Guanglei Cheng
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA
- Pittsburgh Quantum Institute, Pittsburgh, Pennsylvania 15260, USA
| | - Shicheng Lu
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA
- Pittsburgh Quantum Institute, Pittsburgh, Pennsylvania 15260, USA
| | - Michelle Tomczyk
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA
- Pittsburgh Quantum Institute, Pittsburgh, Pennsylvania 15260, USA
| | - Mengchen Huang
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA
- Pittsburgh Quantum Institute, Pittsburgh, Pennsylvania 15260, USA
| | - Chang-Beom Eom
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - Patrick Irvin
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA
- Pittsburgh Quantum Institute, Pittsburgh, Pennsylvania 15260, USA
| | - Jeremy Levy
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA
- Pittsburgh Quantum Institute, Pittsburgh, Pennsylvania 15260, USA
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34
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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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35
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Frenkel Y, Haham N, Shperber Y, Bell C, Xie Y, Chen Z, Hikita Y, Hwang HY, Salje EKH, Kalisky B. Imaging and tuning polarity at SrTiO 3 domain walls. NATURE MATERIALS 2017; 16:1203-1208. [PMID: 28920939 DOI: 10.1038/nmat4966] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/20/2016] [Accepted: 07/13/2017] [Indexed: 06/07/2023]
Abstract
Electrostatic fields tune the ground state of interfaces between complex oxide materials. Electronic properties, such as conductivity and superconductivity, can be tuned and then used to create and control circuit elements and gate-defined devices. Here we show that naturally occurring twin boundaries, with properties that are different from their surrounding bulk, can tune the LaAlO3/SrTiO3 interface 2DEG at the nanoscale. In particular, SrTiO3 domain boundaries have the unusual distinction of remaining highly mobile down to low temperatures, and were recently suggested to be polar. Here we apply localized pressure to an individual SrTiO3 twin boundary and detect a change in LaAlO3/SrTiO3 interface current distribution. Our data directly confirm the existence of polarity at the twin boundaries, and demonstrate that they can serve as effective tunable gates. As the location of SrTiO3 domain walls can be controlled using external field stimuli, our findings suggest a novel approach to manipulate SrTiO3-based devices on the nanoscale.
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Affiliation(s)
- Yiftach Frenkel
- Department of Physics and Institute of Nanotechnology and Advanced Materials, Bar-Ilan University, Ramat-Gan 5290002, Israel
| | - Noam Haham
- Department of Physics and Institute of Nanotechnology and Advanced Materials, Bar-Ilan University, Ramat-Gan 5290002, Israel
| | - Yishai Shperber
- Department of Physics and Institute of Nanotechnology and Advanced Materials, Bar-Ilan University, Ramat-Gan 5290002, Israel
| | - Christopher Bell
- H. H. Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol BS8 1TL, UK
| | - Yanwu Xie
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
- Department of Physics, Zhejiang University, Hangzhou 310027, China
- Department of Applied Physics, Geballe Laboratory for Advanced Materials, Stanford University, 476 Lomita Mall, Stanford University, Stanford, California 94305, USA
| | - Zhuoyu Chen
- Department of Applied Physics, Geballe Laboratory for Advanced Materials, Stanford University, 476 Lomita Mall, Stanford University, Stanford, California 94305, USA
| | - Yasuyuki Hikita
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
| | - Harold Y Hwang
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
- Department of Applied Physics, Geballe Laboratory for Advanced Materials, Stanford University, 476 Lomita Mall, Stanford University, Stanford, California 94305, USA
| | - Ekhard K H Salje
- Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EQ, UK
- State Key Laboratory for Mechanical Behavior of Materials, Xi'an Jiaotong University, Xi'an 710049, China
| | - Beena Kalisky
- Department of Physics and Institute of Nanotechnology and Advanced Materials, Bar-Ilan University, Ramat-Gan 5290002, Israel
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36
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Lange M, Guénon S, Lever F, Kleiner R, Koelle D. A high-resolution combined scanning laser and widefield polarizing microscope for imaging at temperatures from 4 K to 300 K. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2017; 88:123705. [PMID: 29289195 DOI: 10.1063/1.5009529] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Polarized light microscopy, as a contrast-enhancing technique for optically anisotropic materials, is a method well suited for the investigation of a wide variety of effects in solid-state physics, as, for example, birefringence in crystals or the magneto-optical Kerr effect (MOKE). We present a microscopy setup that combines a widefield microscope and a confocal scanning laser microscope with polarization-sensitive detectors. By using a high numerical aperture objective, a spatial resolution of about 240 nm at a wavelength of 405 nm is achieved. The sample is mounted on a 4He continuous flow cryostat providing a temperature range between 4 K and 300 K, and electromagnets are used to apply magnetic fields of up to 800 mT with variable in-plane orientation and 20 mT with out-of-plane orientation. Typical applications of the polarizing microscope are the imaging of the in-plane and out-of-plane magnetization via the longitudinal and polar MOKE, imaging of magnetic flux structures in superconductors covered with a magneto-optical indicator film via the Faraday effect, or imaging of structural features, such as twin-walls in tetragonal SrTiO3. The scanning laser microscope furthermore offers the possibility to gain local information on electric transport properties of a sample by detecting the beam-induced voltage change across a current-biased sample. This combination of magnetic, structural, and electric imaging capabilities makes the microscope a viable tool for research in the fields of oxide electronics, spintronics, magnetism, and superconductivity.
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Affiliation(s)
- M Lange
- Physikalisches Institut-Experimentalphysik II and Center for Quantum Science (CQ) in LISA, Universität Tübingen, D-72076 Tübingen, Germany
| | - S Guénon
- Physikalisches Institut-Experimentalphysik II and Center for Quantum Science (CQ) in LISA, Universität Tübingen, D-72076 Tübingen, Germany
| | - F Lever
- Physikalisches Institut-Experimentalphysik II and Center for Quantum Science (CQ) in LISA, Universität Tübingen, D-72076 Tübingen, Germany
| | - R Kleiner
- Physikalisches Institut-Experimentalphysik II and Center for Quantum Science (CQ) in LISA, Universität Tübingen, D-72076 Tübingen, Germany
| | - D Koelle
- Physikalisches Institut-Experimentalphysik II and Center for Quantum Science (CQ) in LISA, Universität Tübingen, D-72076 Tübingen, Germany
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37
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Minhas MZ, Müller A, Heyroth F, Blaschek HH, Schmidt G. Temperature dependent giant resistance anomaly in LaAlO 3/SrTiO 3 nanostructures. Sci Rep 2017; 7:5215. [PMID: 28701758 PMCID: PMC5507897 DOI: 10.1038/s41598-017-05331-y] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2017] [Accepted: 05/26/2017] [Indexed: 11/09/2022] Open
Abstract
The resistance of the electron gas (2DEG) at the interface between the two band insulators LaAlO3 (LAO) and SrTiO3 (STO) typically drops monotonically with temperature and R/T curves during cooling and warm-up look identical for large area structures. Here we show that if the LAO/STO is laterally restricted by nanopatterning the resistance exhibits a temperature anomaly. Warming up nanostructures from low temperatures leads to one or two pronounced resistance peaks between 50 and 100 K not observed for larger dimensions. During cool-down current filaments emerge at the domain walls that form during a structural phase transition of the STO substrate. During warm-up the reverse phase transition can interrupt filaments before the sheet conductivity which dominates at higher temperature is reestablished. Due to the limited number of filaments in a nanostructure this process can result in a complete loss of conductance. As a consequence of these findings the transport physics extracted from experiments in small and large area LAO/STO structures may need to be reconsidered.
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Affiliation(s)
- M Z Minhas
- Institut für Physik, Martin-Luther-Universität Halle-Wittenberg, Von-Danckelmann-Platz 3, 06120, Halle, Germany
| | - A Müller
- Institut für Physik, Martin-Luther-Universität Halle-Wittenberg, Von-Danckelmann-Platz 3, 06120, Halle, Germany
| | - F Heyroth
- Interdisziplinäres Zentrum für Materialwissenschaften, Martin-Luther-Universität Halle-Wittenberg, Heinrich-Damerow-Str. 4, 06120, Halle, Germany
| | - H H Blaschek
- Institut für Physik, Martin-Luther-Universität Halle-Wittenberg, Von-Danckelmann-Platz 3, 06120, Halle, Germany
| | - G Schmidt
- Institut für Physik, Martin-Luther-Universität Halle-Wittenberg, Von-Danckelmann-Platz 3, 06120, Halle, Germany.
- Interdisziplinäres Zentrum für Materialwissenschaften, Martin-Luther-Universität Halle-Wittenberg, Heinrich-Damerow-Str. 4, 06120, Halle, Germany.
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38
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Strelcov E, Dong Q, Li T, Chae J, Shao Y, Deng Y, Gruverman A, Huang J, Centrone A. CH 3NH 3PbI 3 perovskites: Ferroelasticity revealed. SCIENCE ADVANCES 2017; 3:e1602165. [PMID: 28439542 PMCID: PMC5392022 DOI: 10.1126/sciadv.1602165] [Citation(s) in RCA: 151] [Impact Index Per Article: 21.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/08/2016] [Accepted: 02/19/2017] [Indexed: 05/05/2023]
Abstract
Ferroelectricity has been proposed as a plausible mechanism to explain the high photovoltaic conversion efficiency in organic-inorganic perovskites; however, convincing experimental evidence in support of this hypothesis is still missing. Identifying and distinguishing ferroelectricity from other properties, such as piezoelectricity, ferroelasticity, etc., is typically nontrivial because these phenomena can coexist in many materials. In this work, a combination of microscopic and nanoscale techniques provides solid evidence for the existence of ferroelastic domains in both CH3NH3PbI3 polycrystalline films and single crystals in the pristine state and under applied stress. Experiments show that the configuration of CH3NH3PbI3 ferroelastic domains in single crystals and polycrystalline films can be controlled with applied stress, suggesting that strain engineering may be used to tune the properties of this material. No evidence of concomitant ferroelectricity was observed. Because grain boundaries have an impact on the long-term stability of organic-inorganic perovskite devices, and because the ferroelastic domain boundaries may differ from regular grain boundaries, the discovery of ferroelasticity provides a new variable to consider in the quest for improving their stability and enabling their widespread adoption.
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Affiliation(s)
- Evgheni Strelcov
- Center for Nanoscale Science and Technology, National Institute of Standards and Technology, 100 Bureau Drive, Gaithersburg, MD 20899, USA
- Maryland Nanocenter, University of Maryland, College Park, MD 20742, USA
| | - Qingfeng Dong
- Department of Mechanical and Materials Engineering, University of Nebraska–Lincoln, Lincoln, NE 68588, USA
| | - Tao Li
- Department of Physics and Astronomy, University of Nebraska–Lincoln, Lincoln, NE 68588, USA
| | - Jungseok Chae
- Center for Nanoscale Science and Technology, National Institute of Standards and Technology, 100 Bureau Drive, Gaithersburg, MD 20899, USA
- Maryland Nanocenter, University of Maryland, College Park, MD 20742, USA
| | - Yuchuan Shao
- Department of Mechanical and Materials Engineering, University of Nebraska–Lincoln, Lincoln, NE 68588, USA
- Department of Physics and Astronomy, University of Nebraska–Lincoln, Lincoln, NE 68588, USA
| | - Yehao Deng
- Department of Mechanical and Materials Engineering, University of Nebraska–Lincoln, Lincoln, NE 68588, USA
- Department of Physics and Astronomy, University of Nebraska–Lincoln, Lincoln, NE 68588, USA
| | - Alexei Gruverman
- Department of Physics and Astronomy, University of Nebraska–Lincoln, Lincoln, NE 68588, USA
| | - Jinsong Huang
- Department of Mechanical and Materials Engineering, University of Nebraska–Lincoln, Lincoln, NE 68588, USA
| | - Andrea Centrone
- Center for Nanoscale Science and Technology, National Institute of Standards and Technology, 100 Bureau Drive, Gaithersburg, MD 20899, USA
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39
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Anisotropic electrical resistance in mesoscopic LaAlO 3/SrTiO 3 devices with individual domain walls. Sci Rep 2017; 7:44361. [PMID: 28295058 PMCID: PMC5353628 DOI: 10.1038/srep44361] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2016] [Accepted: 02/08/2017] [Indexed: 11/23/2022] Open
Abstract
The crystal structure of bulk SrTiO3(STO) transitions from cubic to tetragonal at around 105 K. Recent local scanning probe measurements of LaAlO3/SrTiO3 (LAO/STO) interfaces indicated the existence of spatially inhomogeneous electrical current paths and electrostatic potential associated with the structural domain formation in the tetragonal phase of STO. Here we report a study of temperature dependent electronic transport in combination with the polarized light microscopy of structural domains in mesoscopic LAO/STO devices. By reducing the size of the conductive interface to be comparable to that of a single tetragonal domain of STO, the anisotropy of interfacial electron conduction in relationship to the domain wall and its direction was characterized between T = 10–300 K. It was found that the four-point resistance measured with current parallel to the domain wall is larger than the resistance measured perpendicular to the domain wall. This observation is qualitatively consistent with the current diverting effect from a more conductive domain wall within the sample. Among all the samples studied, the maximum resistance ratio found is at least 10 and could be as large as 105 at T = 10 K. This electronic anisotropy may have implications on other oxide hetero-interfaces and the further understanding of electronic/magnetic phenomena found in LAO/STO.
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40
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Monteiro AMRVL, Groenendijk DJ, Manca N, Mulazimoglu E, Goswami S, Blanter Y, Vandersypen LMK, Caviglia AD. Side Gate Tunable Josephson Junctions at the LaAlO 3/SrTiO 3 Interface. NANO LETTERS 2017; 17:715-720. [PMID: 28071920 PMCID: PMC5343548 DOI: 10.1021/acs.nanolett.6b03820] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/12/2016] [Revised: 01/07/2017] [Indexed: 05/22/2023]
Abstract
Novel physical phenomena arising at the interface of complex oxide heterostructures offer exciting opportunities for the development of future electronic devices. Using the prototypical LaAlO3/SrTiO3 interface as a model system, we employ a single-step lithographic process to realize gate-tunable Josephson junctions through a combination of lateral confinement and local side gating. The action of the side gates is found to be comparable to that of a local back gate, constituting a robust and efficient way to control the properties of the interface at the nanoscale. We demonstrate that the side gates enable reliable tuning of both the normal-state resistance and the critical (Josephson) current of the constrictions. The conductance and Josephson current show mesoscopic fluctuations as a function of the applied side gate voltage, and the analysis of their amplitude enables the extraction of the phase coherence and thermal lengths. Finally, we realize a superconducting quantum interference device in which the critical currents of each of the constriction-type Josephson junctions can be controlled independently via the side gates.
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41
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Goswami S, Mulazimoglu E, Monteiro AMRVL, Wölbing R, Koelle D, Kleiner R, Blanter YM, Vandersypen LMK, Caviglia AD. Quantum interference in an interfacial superconductor. NATURE NANOTECHNOLOGY 2016; 11:861-865. [PMID: 27428278 DOI: 10.1038/nnano.2016.112] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/11/2015] [Accepted: 05/23/2016] [Indexed: 06/06/2023]
Abstract
The two-dimensional superconductor that forms at the interface between the complex oxides lanthanum aluminate (LAO) and strontium titanate (STO) has several intriguing properties that set it apart from conventional superconductors. Most notably, an electric field can be used to tune its critical temperature (Tc; ref. 7), revealing a dome-shaped phase diagram reminiscent of high-Tc superconductors. So far, experiments with oxide interfaces have measured quantities that probe only the magnitude of the superconducting order parameter and are not sensitive to its phase. Here, we perform phase-sensitive measurements by realizing the first superconducting quantum interference devices (SQUIDs) at the LAO/STO interface. Furthermore, we develop a new paradigm for the creation of superconducting circuit elements, where local gates enable the in situ creation and control of Josephson junctions. These gate-defined SQUIDs are unique in that the entire device is made from a single superconductor with purely electrostatic interfaces between the superconducting reservoir and the weak link. We complement our experiments with numerical simulations and show that the low superfluid density of this interfacial superconductor results in a large, gate-controllable kinetic inductance of the SQUID. Our observation of robust quantum interference opens up a new pathway to understanding the nature of superconductivity at oxide interfaces.
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Affiliation(s)
- Srijit Goswami
- Kavli Institute of Nanoscience, Delft University of Technology, PO Box 5046, 2600 GA Delft, The Netherlands
| | - Emre Mulazimoglu
- Kavli Institute of Nanoscience, Delft University of Technology, PO Box 5046, 2600 GA Delft, The Netherlands
| | - Ana M R V L Monteiro
- Kavli Institute of Nanoscience, Delft University of Technology, PO Box 5046, 2600 GA Delft, The Netherlands
| | - Roman Wölbing
- Physikalisches Institut and CQ Center for Quantum Science in LISA+, Eberhard Karls Universität Tübingen, Auf der Morgenstelle 14, D-72076 Tübingen, Germany
| | - Dieter Koelle
- Physikalisches Institut and CQ Center for Quantum Science in LISA+, Eberhard Karls Universität Tübingen, Auf der Morgenstelle 14, D-72076 Tübingen, Germany
| | - Reinhold Kleiner
- Physikalisches Institut and CQ Center for Quantum Science in LISA+, Eberhard Karls Universität Tübingen, Auf der Morgenstelle 14, D-72076 Tübingen, Germany
| | - Ya M Blanter
- Kavli Institute of Nanoscience, Delft University of Technology, PO Box 5046, 2600 GA Delft, The Netherlands
| | - Lieven M K Vandersypen
- Kavli Institute of Nanoscience, Delft University of Technology, PO Box 5046, 2600 GA Delft, The Netherlands
| | - Andrea D Caviglia
- Kavli Institute of Nanoscience, Delft University of Technology, PO Box 5046, 2600 GA Delft, The Netherlands
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42
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Tomczyk M, Cheng G, Lee H, Lu S, Annadi A, Veazey JP, Huang M, Irvin P, Ryu S, Eom CB, Levy J. Micrometer-Scale Ballistic Transport of Electron Pairs in LaAlO_{3}/SrTiO_{3} Nanowires. PHYSICAL REVIEW LETTERS 2016; 117:096801. [PMID: 27610871 DOI: 10.1103/physrevlett.117.096801] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/25/2016] [Indexed: 06/06/2023]
Abstract
High-mobility complex-oxide heterostructures and nanostructures offer new opportunities for extending the paradigm of quantum transport beyond the realm of traditional III-V or carbon-based materials. Recent quantum transport investigations with LaAlO_{3}/SrTiO_{3}-based quantum dots reveal the existence of a strongly correlated phase in which electrons form spin-singlet pairs without becoming superconducting. Here, we report evidence for the micrometer-scale ballistic transport of electron pairs in quasi-1D LaAlO_{3}/SrTiO_{3} nanowire cavities. In the paired phase, Fabry-Perot-like quantum interference is observed, in sync with conductance oscillations observed in the superconducting regime (at a zero magnetic field). Above a critical magnetic field B_{p}, the electron pairs unbind and the conductance oscillations shift with the magnetic field. These experimental observations extend the regime of ballistic electronic transport to strongly correlated phases.
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Affiliation(s)
- Michelle Tomczyk
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA
- Pittsburgh Quantum Institute, Pittsburgh, Pennsylvania 15260, USA
| | - Guanglei Cheng
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA
- Pittsburgh Quantum Institute, Pittsburgh, Pennsylvania 15260, USA
| | - Hyungwoo Lee
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - Shicheng Lu
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA
- Pittsburgh Quantum Institute, Pittsburgh, Pennsylvania 15260, USA
| | - Anil Annadi
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA
- Pittsburgh Quantum Institute, Pittsburgh, Pennsylvania 15260, USA
| | - Joshua P Veazey
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA
| | - Mengchen Huang
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA
- Pittsburgh Quantum Institute, Pittsburgh, Pennsylvania 15260, USA
| | - Patrick Irvin
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA
- Pittsburgh Quantum Institute, Pittsburgh, Pennsylvania 15260, USA
| | - Sangwoo Ryu
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - Chang-Beom Eom
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - Jeremy Levy
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA
- Pittsburgh Quantum Institute, Pittsburgh, Pennsylvania 15260, USA
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43
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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}. PHYSICAL REVIEW LETTERS 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] [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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44
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Frenkel Y, Haham N, Shperber Y, Bell C, Xie Y, Chen Z, Hikita Y, Hwang HY, Kalisky B. Anisotropic Transport at the LaAlO3/SrTiO3 Interface Explained by Microscopic Imaging of Channel-Flow over SrTiO3 Domains. ACS APPLIED MATERIALS & INTERFACES 2016; 8:12514-9. [PMID: 27111600 PMCID: PMC5301281 DOI: 10.1021/acsami.6b01655] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/07/2016] [Accepted: 04/25/2016] [Indexed: 05/22/2023]
Abstract
Oxide interfaces, including the LaAlO3/SrTiO3 interface, have been a subject of intense interest for over a decade due to their rich physics and potential as low-dimensional nanoelectronic systems. The field has reached the stage where efforts are invested in developing devices. It is critical now to understand the functionalities and limitations of such devices. Recent scanning probe measurements of the LaAlO3/SrTiO3 interface have revealed locally enhanced current flow and accumulation of charge along channels related to SrTiO3 structural domains. These observations raised a key question regarding the role these modulations play in the macroscopic properties of devices. Here we show that the microscopic picture, mapped by scanning superconducting quantum interference device, accounts for a substantial part of the macroscopically measured transport anisotropy. We compared local flux data with transport values, measured simultaneously, over various SrTiO3 domain configurations. We show a clear relation between maps of local current density over specific domain configurations and the measured anisotropy for the same device. The domains divert the direction of current flow, resulting in a direction-dependent resistance. We also show that the modulation can be significant and that in some cases up to 95% of the current is modulated over the channels. The orientation and distribution of the SrTiO3 structural domains change between different cooldowns of the same device or when electric fields are applied, affecting the device behavior. Our results, highlight the importance of substrate physics, and in particular, the role of structural domains, in controlling electronic properties of LaAlO3/SrTiO3 devices. Furthermore, these results point to new research directions, exploiting the STO domains' ability to divert or even carry current.
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Affiliation(s)
- Yiftach Frenkel
- Department of Physics
and Institute of Nanotechnology and Advanced Materials, Bar-Ilan University, Ramat-Gan 5290002, Israel
| | - Noam Haham
- Department of Physics
and Institute of Nanotechnology and Advanced Materials, Bar-Ilan University, Ramat-Gan 5290002, Israel
| | - Yishai Shperber
- Department of Physics
and Institute of Nanotechnology and Advanced Materials, Bar-Ilan University, Ramat-Gan 5290002, Israel
| | - Christopher Bell
- H. H. Wills Physics Laboratory, University
of Bristol, Tyndall Avenue, Bristol BS8 1TL, United Kingdom
| | - Yanwu Xie
- Stanford Institute for Materials and Energy
Sciences, SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States
- Department of Physics, Zhejiang University, Hangzhou 310027, China
| | - Zhuoyu Chen
- Department of Applied Physics, Geballe
Laboratory for Advanced Materials, Stanford
University 476 Lomita
Mall, 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
| | - Harold Y. Hwang
- Stanford Institute for Materials and Energy
Sciences, SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States
- Department of Applied Physics, Geballe
Laboratory for Advanced Materials, Stanford
University 476 Lomita
Mall, Stanford University, Stanford, California 94305, United States
| | - Beena Kalisky
- Department of Physics
and Institute of Nanotechnology and Advanced Materials, Bar-Ilan University, Ramat-Gan 5290002, Israel
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45
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Chen Z, Li J. A new method applicable to study solid compounds with multiple polyhedral structures. J Comput Chem 2016; 37:1476-83. [DOI: 10.1002/jcc.24360] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2016] [Revised: 02/16/2016] [Accepted: 02/22/2016] [Indexed: 11/09/2022]
Affiliation(s)
- Zhenlian Chen
- Ningbo Institute of Material Technology and Engineering, Chinese Academy of Sciences; Ningbo 315201 People's Republic of China
| | - Jun Li
- Ningbo Institute of Material Technology and Engineering, Chinese Academy of Sciences; Ningbo 315201 People's Republic of China
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46
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Ngo TDN, Chang JW, Lee K, Han S, Lee JS, Kim YH, Jung MH, Doh YJ, Choi MS, Song J, Kim J. Polarity-tunable magnetic tunnel junctions based on ferromagnetism at oxide heterointerfaces. Nat Commun 2015; 6:8035. [PMID: 26268611 PMCID: PMC4557347 DOI: 10.1038/ncomms9035] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2014] [Accepted: 07/08/2015] [Indexed: 11/15/2022] Open
Abstract
Complex oxide systems have attracted considerable attention because of their fascinating properties, including the magnetic ordering at the conducting interface between two band insulators, such as LaAlO3 and SrTiO3. However, the manipulation of the spin degree of freedom at the LaAlO3/SrTiO3 heterointerface has remained elusive. Here, we have fabricated hybrid magnetic tunnel junctions consisting of Co and LaAlO3/SrTiO3 ferromagnets with the insertion of a Ti layer in between, which clearly exhibit magnetic switching and the tunnelling magnetoresistance effect below 10 K. The magnitude and sign of the tunnelling magnetoresistance are strongly dependent on the direction of the rotational magnetic field parallel to the LaAlO3/SrTiO3 plane, which is attributed to a strong Rashba-type spin-orbit coupling in the LaAlO3/SrTiO3 heterostructure. Our study provides a further support for the existence of the macroscopic ferromagnetism at LaAlO3/SrTiO3 heterointerfaces and opens a novel route to realize interfacial spintronics devices. The interface between two insulating oxides can play host to magnetic ordering. Here, the authors manipulate the spin transport in a hybrid magnetic tunnel junction comprising two ferromagnets: one a cobalt layer and the other the interface between lanthanum aluminate and strontium titanate.
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Affiliation(s)
- Thach D N Ngo
- Korea Research Institute of Standards and Science, Daejeon 305-340, Korea.,Department of Nanoscience, Korea University of Science and Technology, Daejeon 305-350, Korea
| | - Jung-Won Chang
- Korea Research Institute of Standards and Science, Daejeon 305-340, Korea.,Department of Applied Physics, Korea University Sejong Campus, Sejong 339-700, Korea
| | - Kyujoon Lee
- Department of Physics, Sogang University, Seoul 121-742, Korea
| | - Seungju Han
- Department of Physics, Korea University, Seoul 136-713, Korea
| | - Joon Sung Lee
- Department of Applied Physics, Korea University Sejong Campus, Sejong 339-700, Korea
| | - Young Heon Kim
- Korea Research Institute of Standards and Science, Daejeon 305-340, Korea
| | - Myung-Hwa Jung
- Department of Physics, Sogang University, Seoul 121-742, Korea
| | - Yong-Joo Doh
- Department of Applied Physics, Korea University Sejong Campus, Sejong 339-700, Korea
| | - Mahn-Soo Choi
- Department of Physics, Korea University, Seoul 136-713, Korea
| | - Jonghyun Song
- Department of Physics, Chungnam National University, Daejeon 305-764, Korea
| | - Jinhee Kim
- Korea Research Institute of Standards and Science, Daejeon 305-340, Korea
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47
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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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48
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Nazir S, Cheng J, Behtash M, Luo J, Yang K. Interface Energetics and Charge Carrier Density Amplification by Sn-Doping in LaAlO3/SrTiO3 Heterostructure. ACS APPLIED MATERIALS & INTERFACES 2015; 7:14294-14302. [PMID: 26062403 DOI: 10.1021/acsami.5b02770] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Tailoring the two-dimensional electron gas (2DEG) at the n-type (TiO2)(0)/(LaO)(+1) interface between the polar LaAlO3 (LAO) and nonpolar SrTiO3 (STO) insulators can potentially provide desired functionalities for next-generation low-dimensional nanoelectronic devices. Here, we propose a new approach to tune the electronic and magnetic properties in the n-type LAO/STO heterostructure (HS) system via electron doping. In this work, we modeled four types of layer doped LAO/STO HS systems with Sn dopants at different cation sites and studied their electronic structures and interface energetics by using first-principles electronic structure calculations. We identified the thermodynamic stability conditions for each of the four proposed doped configurations with respect to the undoped LAO/STO interface. We further found that the Sn-doped LAO/STO HS system with Sn at Al site (Sn@Al) is energetically most favorable with respect to decohesion, thereby strengthening the interface, while the doped HS system with Sn at La site (Sn@La) exhibits the lowest interfacial cohesion. Moreover, our results indicate that all the Sn-doped LAO/STO HS systems exhibit the n-type conductivity with the typical 2DEG characteristics except the Sn@La doped HS system, which shows p-type conductivity. In the Sn@Al doped HS model, the Sn dopant exists as a Sn(4+) ion and introduces one additional electron into the HS system, leading to a higher charge carrier density and larger magnetic moment than that of all the other doped HS systems. An enhanced charge confinement of the 2DEG along the c-axis is also found in the Sn@Al doped HS system. We hence suggest that Sn@Al doping can be an effective way to enhance the electrical conduction and magnetic moment of the 2DEG in LAO/STO HS systems in an energetically favorable manner.
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Affiliation(s)
- Safdar Nazir
- Department of NanoEngineering, University of California, San Diego, 9500 Gilman Drive, Mail Code 0448, La Jolla, California 92093-0448, United States
| | - Jianli Cheng
- Department of NanoEngineering, University of California, San Diego, 9500 Gilman Drive, Mail Code 0448, La Jolla, California 92093-0448, United States
| | - Maziar Behtash
- Department of NanoEngineering, University of California, San Diego, 9500 Gilman Drive, Mail Code 0448, La Jolla, California 92093-0448, United States
| | - Jian Luo
- Department of NanoEngineering, University of California, San Diego, 9500 Gilman Drive, Mail Code 0448, La Jolla, California 92093-0448, United States
| | - Kesong Yang
- Department of NanoEngineering, University of California, San Diego, 9500 Gilman Drive, Mail Code 0448, La Jolla, California 92093-0448, United States
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49
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Goswami S, Mulazimoglu E, Vandersypen LMK, Caviglia AD. Nanoscale electrostatic control of oxide interfaces. NANO LETTERS 2015; 15:2627-2632. [PMID: 25749273 DOI: 10.1021/acs.nanolett.5b00216] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We develop a robust and versatile platform to define nanostructures at oxide interfaces via patterned top gates. Using LaAlO3/SrTiO3 as a model system, we demonstrate controllable electrostatic confinement of electrons to nanoscale regions in the conducting interface. The excellent gate response, ultralow leakage currents, and long-term stability of these gates allow us to perform a variety of studies in different device geometries from room temperature down to 50 mK. Using a split-gate device we demonstrate the formation of a narrow conducting channel whose width can be controllably reduced via the application of appropriate gate voltages. We also show that a single narrow gate can be used to induce locally a superconducting to insulating transition. Furthermore, in the superconducting regime we see indications of a gate-voltage controlled Josephson effect.
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Affiliation(s)
- Srijit Goswami
- Kavli Institute of Nanoscience, Delft University of Technology, P.O. Box 5046, 2600 GA Delft, The Netherlands
| | - Emre Mulazimoglu
- Kavli Institute of Nanoscience, Delft University of Technology, P.O. Box 5046, 2600 GA Delft, The Netherlands
| | - Lieven M K Vandersypen
- Kavli Institute of Nanoscience, Delft University of Technology, P.O. Box 5046, 2600 GA Delft, The Netherlands
| | - Andrea D Caviglia
- Kavli Institute of Nanoscience, Delft University of Technology, P.O. Box 5046, 2600 GA Delft, The Netherlands
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50
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Maerten L, Bojahr A, Gohlke M, Rössle M, Bargheer M. Coupling of GHz phonons to ferroelastic domain walls in SrTiO3. PHYSICAL REVIEW LETTERS 2015; 114:047401. [PMID: 25679906 DOI: 10.1103/physrevlett.114.047401] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/01/2013] [Indexed: 06/04/2023]
Abstract
We study the linear and nonlinear acoustic response of SrTiO3 across its ferroelastic transition at Ta=105 K by time domain Brillouin scattering. Above Ta we observe that for a strain amplitude of ∼0.18% the sound velocity for compressive strain exceeds the tensile strain velocity by 3%. Below Ta we find a giant slowing down of the sound velocity by 12% and attribute this to the coupling of GHz phonons to ferroelastic twin domain walls. We propose a new mechanism for this coupling on the ultrafast time scale, providing an important new test ground for theories used to simulate atomic motion in domain forming crystals.
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Affiliation(s)
- L Maerten
- Institut für Physik & Astronomie, Universität Potsdam, Karl-Liebknecht-Strasse 24-25, 14476 Potsdam, Germany
| | - A Bojahr
- Institut für Physik & Astronomie, Universität Potsdam, Karl-Liebknecht-Strasse 24-25, 14476 Potsdam, Germany
| | - M Gohlke
- Institut für Physik & Astronomie, Universität Potsdam, Karl-Liebknecht-Strasse 24-25, 14476 Potsdam, Germany
| | - M Rössle
- Institut für Physik & Astronomie, Universität Potsdam, Karl-Liebknecht-Strasse 24-25, 14476 Potsdam, Germany
| | - M Bargheer
- Institut für Physik & Astronomie, Universität Potsdam, Karl-Liebknecht-Strasse 24-25, 14476 Potsdam, Germany and Helmholtz-Zentrum-Berlin für Energie und Materialforschung, Wilhelm-Conrad-Röntgen Campus, BESSY II, Albert-Einstein-Strasse 15, 12489 Berlin, Germany
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