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D'Antuono M, Chen Y, Caruso R, Jouault B, Salluzzo M, Stornaiuolo D. Tuning of the magnetotransport properties of a spin-polarized 2D electron system using visible light. Sci Rep 2023; 13:10050. [PMID: 37344495 DOI: 10.1038/s41598-023-36957-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2023] [Accepted: 06/13/2023] [Indexed: 06/23/2023] Open
Abstract
We report on the effects of visible light on the low temperature electronic properties of the spin-polarized two dimensional electron system (2DES) formed at the interfaces between LaAlO[Formula: see text], EuTiO[Formula: see text] and (001) SrTiO[Formula: see text]. A strong, persistent modulation of both longitudinal and transverse conductivity was obtained using light emitting diodes (LEDs) with emissions at different wavelengths in the visible spectrum range. In particular, Hall effect data show that visible light induces a non-volatile electron filling of bands with mainly 3d[Formula: see text] character, and at the same time an enhancement of the anomalous Hall effect associated to the magnetic properties of the system. Accordingly, a suppression of the weak-anti localization corrections to the magneto-conductance is found, which correlates with an enhancement of the spin-polarization and of the ferromagnetic character of 2DES. The results establish the LED-induced photo-doping as a viable route for the control of the ground state properties of artificial spin-polarized oxide 2DES.
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Affiliation(s)
- Maria D'Antuono
- Department of Physics, University of Naples Federico II, via Cinthia, 80126, Naples, Italy
- CNR-SPIN, via Cinthia, 80126, Naples, Italy
| | - Yu Chen
- CNR-SPIN, via Cinthia, 80126, Naples, Italy
| | - Roberta Caruso
- Department of Physics, University of Naples Federico II, via Cinthia, 80126, Naples, Italy
- CNR-SPIN, via Cinthia, 80126, Naples, Italy
- Condensed Matter Physics and Materials Science Division, Brookhaven National Laboratory, Bldg. 480, P.O. Box 5000, Upton, NY, 11973-5000, USA
| | - Benoit Jouault
- Laboratoire Charles Coulomb, UMR 5221, CNRS, Université de Montpellier, 34095, Montpellier, France
| | | | - Daniela Stornaiuolo
- Department of Physics, University of Naples Federico II, via Cinthia, 80126, Naples, Italy.
- CNR-SPIN, via Cinthia, 80126, Naples, Italy.
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2
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Rose MA, Šmíd B, Vorokhta M, Slipukhina I, Andrä M, Bluhm H, Duchoň T, Ležaić M, Chambers SA, Dittmann R, Mueller DN, Gunkel F. Identifying Ionic and Electronic Charge Transfer at Oxide Heterointerfaces. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2021; 33:e2004132. [PMID: 33263190 DOI: 10.1002/adma.202004132] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/17/2020] [Revised: 08/31/2020] [Indexed: 06/12/2023]
Abstract
The ability to tailor oxide heterointerfaces has led to novel properties in low-dimensional oxide systems. A fundamental understanding of these properties is based on the concept of electronic charge transfer. However, the electronic properties of oxide heterointerfaces crucially depend on their ionic constitution and defect structure: ionic charges contribute to charge transfer and screening at oxide interfaces, triggering a thermodynamic balance of ionic and electronic structures. Quantitative understanding of the electronic and ionic roles regarding charge-transfer phenomena poses a central challenge. Here, the electronic and ionic structure is simultaneously investigated at the prototypical charge-transfer heterointerface, LaAlO3 /SrTiO3 . Applying in situ photoemission spectroscopy under oxygen ambient, ionic and electronic charge transfer is deconvoluted in response to the oxygen atmosphere at elevated temperatures. In this way, both the rich and variable chemistry of complex oxides and the associated electronic properties are equally embraced. The interfacial electron gas is depleted through an ionic rearrangement in the strontium cation sublattice when oxygen is applied, resulting in an inverse and reversible balance between cation vacancies and electrons, while the mobility of ionic species is found to be considerably enhanced as compared to the bulk. Triggered by these ionic phenomena, the electronic transport and magnetic signature of the heterointerface are significantly altered.
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Affiliation(s)
- Marc-André Rose
- Institute for Electronic Materials (IWE 2), and Juelich-Aachen Research Alliance for Fundamentals on Future Information Technology (JARA-FIT), RWTH Aachen University, 52074, Aachen, Germany
- Peter Grünberg Institute 7, Forschungszentrum Jülich GmbH, and JARA-FIT, 52425, Jülich, Germany
| | - Břetislav Šmíd
- Department of Surface and Plasma Science, Faculty of Mathematics and Physics, Charles University, Prague, 180 00, Czech Republic
| | - Mykhailo Vorokhta
- Department of Surface and Plasma Science, Faculty of Mathematics and Physics, Charles University, Prague, 180 00, Czech Republic
| | - Ivetta Slipukhina
- Peter Grünberg Institute 1 and Institute for Advanced Simulation, Forschungszentrum Jülich GmbH and JARA-FIT, 52425, Jülich, Germany
| | - Michael Andrä
- Peter Grünberg Institute 7, Forschungszentrum Jülich GmbH, and JARA-FIT, 52425, Jülich, Germany
| | - Hendrik Bluhm
- Chemical Sciences Division, Lawrence Berkeley National Lab., Berkeley, CA, 94720, USA
- Department of Inorganic Chemistry, Fritz Haber Institute of the Max Planck Society, 14195, Berlin, Germany
| | - Tomáš Duchoň
- Peter Grünberg Institute 6, and JARA-FIT, Forschungszentrum Jülich GmbH, 52425, Jülich, Germany
| | - Marjana Ležaić
- Peter Grünberg Institute 1 and Institute for Advanced Simulation, Forschungszentrum Jülich GmbH and JARA-FIT, 52425, Jülich, Germany
| | - Scott A Chambers
- Physical and Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland, WA, 99354, USA
| | - Regina Dittmann
- Peter Grünberg Institute 7, Forschungszentrum Jülich GmbH, and JARA-FIT, 52425, Jülich, Germany
| | - David N Mueller
- Peter Grünberg Institute 7, Forschungszentrum Jülich GmbH, and JARA-FIT, 52425, Jülich, Germany
- Peter Grünberg Institute 6, and JARA-FIT, Forschungszentrum Jülich GmbH, 52425, Jülich, Germany
| | - Felix Gunkel
- Institute for Electronic Materials (IWE 2), and Juelich-Aachen Research Alliance for Fundamentals on Future Information Technology (JARA-FIT), RWTH Aachen University, 52074, Aachen, Germany
- Peter Grünberg Institute 7, Forschungszentrum Jülich GmbH, and JARA-FIT, 52425, Jülich, Germany
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3
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Gunnink PM, Bouwmeester RL, Brinkman A. Artificial oxide heterostructures with non-trivial topology. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2020; 33:085601. [PMID: 33176291 DOI: 10.1088/1361-648x/abc973] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
In the quest for topological insulators with large band gaps, heterostructures with Rashba spin-orbit interactions come into play. Transition metal oxides with heavy ions are especially interesting in this respect. We discuss the design principles for stacking oxide Rashba layers. Assuming a single layer with a two-dimensional electron gas (2DEG) on both interfaces as a building block, a two-dimensional topological insulating phase is present when negative coupling between the 2DEGs exists. When stacking multiple building blocks, a two-dimensional or three-dimensional topological insulator is artificially created, depending on the intra- and interlayer coupling strengths and the number of building blocks. We show that the three-dimensional topological insulator is protected by reflection symmetry, and can therefore be classified as a topological crystalline insulator. In order to isolate the topological states from bulk states, the intralayer coupling term needs to be quadratic in momentum. It is described how such a quadratic coupling could potentially be realized by taking buckling within the layers into account. The buckling, thereby, brings the idea of stacked Rashba system very close to the alternative approach of realizing the buckled honeycomb lattice in [111]-oriented perovskite oxides.
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Affiliation(s)
- Pieter M Gunnink
- Faculty of Science and Technology and MESA+ Institute for Nanotechnology, University of Twente, 7500 AE Enschede, The Netherlands
| | - Rosa Luca Bouwmeester
- Faculty of Science and Technology and MESA+ Institute for Nanotechnology, University of Twente, 7500 AE Enschede, The Netherlands
| | - Alexander Brinkman
- Faculty of Science and Technology and MESA+ Institute for Nanotechnology, University of Twente, 7500 AE Enschede, The Netherlands
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4
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Chapman KS, Atkinson WA. Modified transverse Ising model for the dielectric properties of SrTiO 3 films and interfaces. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2020; 32:065303. [PMID: 31634883 DOI: 10.1088/1361-648x/ab4fa7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
The transverse Ising model (TIM), with pseudospins representing the lattice polarization, is often used as a simple description of ferroelectric materials. However, we demonstrate that the TIM, as it is usually formulated, provides an incorrect description of SrTiO3 films and interfaces because of its inadequate treatment of spatial inhomogeneity. We correct this deficiency by adding a pseudospin anisotropy to the model. We demonstrate the physical need for this term by comparison of the TIM to a typical Landau-Ginzburg-Devonshire model. We then demonstrate the physical consequences of the modification for two model systems: a ferroelectric thin film, and a metallic LaAlO3/SrTiO3 interface. We show that, in both cases, the modified TIM has a substantially different polarization profile than the conventional TIM. In particular, at low temperatures the formation of quantized states at LaAlO3/SrTiO3 interfaces only occurs in the modified TIM.
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Affiliation(s)
- Kelsey S Chapman
- Department of Physics and Astronomy, Trent University, Peterborough, Ontario, K9L 0G2, Canada
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5
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Yin C, Smink AEM, Leermakers I, Tang LMK, Lebedev N, Zeitler U, van der Wiel WG, Hilgenkamp H, Aarts J. Electron Trapping Mechanism in LaAlO_{3}/SrTiO_{3} Heterostructures. PHYSICAL REVIEW LETTERS 2020; 124:017702. [PMID: 31976734 DOI: 10.1103/physrevlett.124.017702] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/24/2019] [Revised: 09/13/2019] [Indexed: 06/10/2023]
Abstract
In LaAlO_{3}/SrTiO_{3} heterostructures, a still poorly understood phenomenon is that of electron trapping in back-gating experiments. Here, by combining magnetotransport measurements and self-consistent Schrödinger-Poisson calculations, we obtain an empirical relation between the amount of trapped electrons and the gate voltage. The amount of trapped electrons decays exponentially away from the interface. However, contrary to earlier observations, we find that the Fermi level remains well within the quantum well. The enhanced trapping of electrons induced by the gate voltage can therefore not be explained by a thermal escape mechanism. Further gate sweeping experiments strengthen that conclusion. We propose a new mechanism which involves the electromigration and clustering of oxygen vacancies in SrTiO_{3} and argue that such electron trapping is a universal phenomenon in SrTiO_{3}-based two-dimensional electron systems.
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Affiliation(s)
- Chunhai Yin
- Huygens-Kamerlingh Onnes Laboratory, Leiden University, P.O. Box 9504, 2300 RA Leiden, The Netherlands
| | - Alexander E M Smink
- MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
| | - Inge Leermakers
- High Field Magnet Laboratory (HFML-EMFL), Radboud University, Toernooiveld 7, 6525 ED Nijmegen, The Netherlands
| | - Lucas M K Tang
- High Field Magnet Laboratory (HFML-EMFL), Radboud University, Toernooiveld 7, 6525 ED Nijmegen, The Netherlands
| | - Nikita Lebedev
- Huygens-Kamerlingh Onnes Laboratory, Leiden University, P.O. Box 9504, 2300 RA Leiden, The Netherlands
| | - Uli Zeitler
- High Field Magnet Laboratory (HFML-EMFL), Radboud University, Toernooiveld 7, 6525 ED Nijmegen, The Netherlands
| | - Wilfred G van der Wiel
- MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
| | - Hans Hilgenkamp
- MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
| | - Jan Aarts
- Huygens-Kamerlingh Onnes Laboratory, Leiden University, P.O. Box 9504, 2300 RA Leiden, The Netherlands
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6
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Chikina A, Lechermann F, Husanu MA, Caputo M, Cancellieri C, Wang X, Schmitt T, Radovic M, Strocov VN. Orbital Ordering of the Mobile and Localized Electrons at Oxygen-Deficient LaAlO 3/SrTiO 3 Interfaces. ACS NANO 2018; 12:7927-7935. [PMID: 29995384 DOI: 10.1021/acsnano.8b02335] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Interfacing different transition-metal oxides opens a route to functionalizing their rich interplay of electron, spin, orbital, and lattice degrees of freedom for electronic and spintronic devices. Electronic and magnetic properties of SrTiO3-based interfaces hosting a mobile two-dimensional electron system (2DES) are strongly influenced by oxygen vacancies, which form an electronic dichotomy, where strongly correlated localized electrons in the in-gap states (IGSs) coexist with noncorrelated delocalized 2DES. Here, we use resonant soft-X-ray photoelectron spectroscopy to prove the eg character of the IGSs, as opposed to the t2g character of the 2DES in the paradigmatic LaAlO3/SrTiO3 interface. We furthermore separate the d xy and d xz/d xz orbital contributions based on deeper consideration of the resonant photoexcitation process in terms of orbital and momentum selectivity. Supported by a self-consistent combination of density functional theory and dynamical mean field theory calculations, this experiment identifies local orbital reconstruction that goes beyond the conventional eg- vs-t2g band ordering. A hallmark of oxygen-deficient LaAlO3/SrTiO3 is a significant hybridization of the eg and t2g orbitals. Our findings provide routes for tuning the electronic and magnetic properties of oxide interfaces through "defect engineering" with oxygen vacancies.
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Affiliation(s)
- Alla Chikina
- Swiss Light Source, Paul Scherrer Institute , Villigen CH-5232 , Switzerland
| | - Frank Lechermann
- Institut für Theoretische Physik , Universität Hamburg , Jungiusstrasse 9 , Hamburg DE-20355 , Germany
| | - Marius-Adrian Husanu
- Swiss Light Source, Paul Scherrer Institute , Villigen CH-5232 , Switzerland
- National Institute of Materials Physics , Atomistilor 405A , Magurele RO-077125 , Romania
| | - Marco Caputo
- Swiss Light Source, Paul Scherrer Institute , Villigen CH-5232 , Switzerland
| | - Claudia Cancellieri
- Swiss Light Source, Paul Scherrer Institute , Villigen CH-5232 , Switzerland
- Empa, Swiss Federal Laboratories for Materials Science & Technology , Ueberlandstrasse 129 , Duebendorf CH-8600 , Switzerland
| | - Xiaoqiang Wang
- Swiss Light Source, Paul Scherrer Institute , Villigen CH-5232 , Switzerland
| | - Thorsten Schmitt
- Swiss Light Source, Paul Scherrer Institute , Villigen CH-5232 , Switzerland
| | - Milan Radovic
- Swiss Light Source, Paul Scherrer Institute , Villigen CH-5232 , Switzerland
| | - Vladimir N Strocov
- Swiss Light Source, Paul Scherrer Institute , Villigen CH-5232 , Switzerland
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7
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Pai YY, Tylan-Tyler A, Irvin P, Levy J. Physics of SrTiO 3-based heterostructures and nanostructures: a review. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2018; 81:036503. [PMID: 29424362 DOI: 10.1088/1361-6633/aa892d] [Citation(s) in RCA: 51] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
This review provides a summary of the rich physics expressed within SrTiO3-based heterostructures and nanostructures. The intended audience is researchers who are working in the field of oxides, but also those with different backgrounds (e.g., semiconductor nanostructures). After reviewing the relevant properties of SrTiO3 itself, we will then discuss the basics of SrTiO3-based heterostructures, how they can be grown, and how devices are typically fabricated. Next, we will cover the physics of these heterostructures, including their phase diagram and coupling between the various degrees of freedom. Finally, we will review the rich landscape of quantum transport phenomena, as well as the devices that elicit them.
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Affiliation(s)
- Yun-Yi Pai
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA 15260, United States of America. Pittsburgh Quantum Institute, Pittsburgh, PA 15260, United States of America
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8
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Electrons and Polarons at Oxide Interfaces Explored by Soft-X-Ray ARPES. SPECTROSCOPY OF COMPLEX OXIDE INTERFACES 2018. [DOI: 10.1007/978-3-319-74989-1_6] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
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9
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Wang Y, Ramaswamy R, Motapothula M, Narayanapillai K, Zhu D, Yu J, Venkatesan T, Yang H. Room-Temperature Giant Charge-to-Spin Conversion at the SrTiO 3-LaAlO 3 Oxide Interface. NANO LETTERS 2017; 17:7659-7664. [PMID: 29112444 DOI: 10.1021/acs.nanolett.7b03714] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The two-dimensional electron gas (2DEG) formed at the interface between SrTiO3 (STO) and LaAlO3 (LAO) insulating layer is supposed to possess strong Rashba spin-orbit coupling. To date, the inverse Edelstein effect (i.e., spin-to-charge conversion) in the 2DEG layer is reported. However, the direct effect of charge-to-spin conversion, an essential ingredient for spintronic devices in a current-induced spin-orbit torque scheme, has not been demonstrated yet. Here we show, for the first time, a highly efficient spin generation with the efficiency of ∼6.3 in the STO/LAO/CoFeB structure at room temperature by using spin torque ferromagnetic resonance. In addition, we suggest that the spin transmission through the LAO layer at a high temperature range is attributed to the inelastic tunneling via localized states in the LAO band gap. Our findings may lead to potential applications in the oxide insulator based spintronic devices.
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Affiliation(s)
- Yi Wang
- Department of Electrical and Computer Engineering, NUSNNI, National University of Singapore , 117576 Singapore
| | - Rajagopalan Ramaswamy
- Department of Electrical and Computer Engineering, NUSNNI, National University of Singapore , 117576 Singapore
| | - Mallikarjuna Motapothula
- Department of Electrical and Computer Engineering, NUSNNI, National University of Singapore , 117576 Singapore
| | | | - Dapeng Zhu
- Department of Electrical and Computer Engineering, NUSNNI, National University of Singapore , 117576 Singapore
| | - Jiawei Yu
- Department of Electrical and Computer Engineering, NUSNNI, National University of Singapore , 117576 Singapore
| | - Thirumalai Venkatesan
- Department of Electrical and Computer Engineering, NUSNNI, National University of Singapore , 117576 Singapore
- Department of Physics, National University of Singapore , 117542 Singapore
| | - Hyunsoo Yang
- Department of Electrical and Computer Engineering, NUSNNI, National University of Singapore , 117576 Singapore
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10
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Chen Y, Green RJ, Sutarto R, He F, Linderoth S, Sawatzky GA, Pryds N. Tuning the Two-Dimensional Electron Liquid at Oxide Interfaces by Buffer-Layer-Engineered Redox Reactions. NANO LETTERS 2017; 17:7062-7066. [PMID: 29053919 DOI: 10.1021/acs.nanolett.7b03744] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Polar discontinuities and redox reactions provide alternative paths to create two-dimensional electron liquids (2DELs) at oxide interfaces. Herein, we report high mobility 2DELs at interfaces involving SrTiO3 (STO) achieved using polar La7/8Sr1/8MnO3 (LSMO) buffer layers to manipulate both polarities and redox reactions from disordered overlayers grown at room temperature. Using resonant X-ray reflectometry experiments, we quantify redox reactions from oxide overlayers on STO as well as polarity induced electronic reconstruction at epitaxial LSMO/STO interfaces. The analysis reveals how these effects can be combined in a STO/LSMO/disordered film trilayer system to yield high mobility modulation doped 2DELs, where the buffer layer undergoes a partial transformation from perovskite to brownmillerite structure. This uncovered interplay between polar discontinuities and redox reactions via buffer layers provides a new approach for the design of functional oxide interfaces.
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Affiliation(s)
- Yunzhong Chen
- Department of Energy Conversion and Storage, Technical University of Denmark , Risø campus, 4000 Roskilde, Denmark
| | - Robert J Green
- Stewart Blusson Quantum Matter Institute, Department of Physics and Astronomy, University of British Columbia , Vancouver, British Columbia V6T 1Z4, Canada
- Max Planck Institute for Chemical Physics of Solids , Nothnitzerstraβe 40, 01187 Dresden, Germany
| | - Ronny Sutarto
- Canadian Light Source , Saskatoon, Saskatchewan S7N 2V3, Canada
| | - Feizhou He
- Canadian Light Source , Saskatoon, Saskatchewan S7N 2V3, Canada
| | - Søren Linderoth
- Department of Energy Conversion and Storage, Technical University of Denmark , Risø campus, 4000 Roskilde, Denmark
| | - George A Sawatzky
- Stewart Blusson Quantum Matter Institute, Department of Physics and Astronomy, University of British Columbia , Vancouver, British Columbia V6T 1Z4, Canada
| | - Nini Pryds
- Department of Energy Conversion and Storage, Technical University of Denmark , Risø campus, 4000 Roskilde, Denmark
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11
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Gunkel F, Heinen RA, Hoffmann-Eifert S, Jin L, Jia CL, Dittmann R. Mobility Modulation and Suppression of Defect Formation in Two-Dimensional Electron Systems by Charge-Transfer Management. ACS APPLIED MATERIALS & INTERFACES 2017; 9:10888-10896. [PMID: 28262026 DOI: 10.1021/acsami.7b00905] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Electron mobility is one of the most-debated key attributes of low-dimensional electron systems emerging at complex oxide heterointerfaces. However, a common understanding of how electron mobility can be optimized in these systems has not been achieved so far. Here, we discuss a novel approach for achieving a systematic increase in electron mobility in polar/nonpolar perovskite interfaces by suppressing the thermodynamically required defect formation at the nanoscale. We discuss the transport properties of electron gases established at interfaces between SrTiO3 and various polar perovskites [LaAlO3, NdGaO3, and (La,Sr)(Al,Ta)O3], allowing for the individual variation of epitaxial strain and charge transfer among these epitaxial interfaces. As we show, the reduced charge transfer at (La,Sr)(Al,Ta)O3/SrTiO3 interfaces yields a systematic increase in electron mobility, while the reduced epitaxial strain has only minor impact. As thermodynamic continuum simulations suggest, the charge transfer across these interfaces affects both the spatial distribution of electrons and the background distribution of ionic defects, acting as major scatter centers within the potential well. Easing charge transfer in (La,Sr)(Al,Ta)O3/SrTiO3 yields an enlarged spatial separation of mobile charge carriers and scattering centers, as well as a reduced driving force for the formation of ionic defects at the nanoscale. Our results suggest a general recipe for achieving electron enhancements at oxide heterostructure interfaces and provide new perspectives for atomistic understanding of electron scattering in these systems.
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Affiliation(s)
- Felix Gunkel
- Institute of Electronic Materials, RWTH Aachen University , 52062 Aachen, Germany
- Peter Grünberg Institute, Fundamentals of Future Information Technology, Jülich Aachen Research Alliance, Forschungszentrum Jülich , 52425 Jülich, Germany
| | - Ronja A Heinen
- Peter Grünberg Institute, Fundamentals of Future Information Technology, Jülich Aachen Research Alliance, Forschungszentrum Jülich , 52425 Jülich, Germany
| | - Susanne Hoffmann-Eifert
- Peter Grünberg Institute, Fundamentals of Future Information Technology, Jülich Aachen Research Alliance, Forschungszentrum Jülich , 52425 Jülich, Germany
| | - Lei Jin
- Peter Grünberg Institute, Fundamentals of Future Information Technology, Jülich Aachen Research Alliance, Forschungszentrum Jülich , 52425 Jülich, Germany
- Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons, Forschungszentrum Jülich , 52425 Jülich, Germany
| | - Chun-Lin Jia
- Peter Grünberg Institute, Fundamentals of Future Information Technology, Jülich Aachen Research Alliance, Forschungszentrum Jülich , 52425 Jülich, Germany
- Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons, Forschungszentrum Jülich , 52425 Jülich, Germany
| | - Regina Dittmann
- Peter Grünberg Institute, Fundamentals of Future Information Technology, Jülich Aachen Research Alliance, Forschungszentrum Jülich , 52425 Jülich, Germany
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12
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Smink AEM, de Boer JC, Stehno MP, Brinkman A, van der Wiel WG, Hilgenkamp H. Gate-Tunable Band Structure of the LaAlO_{3}-SrTiO_{3} Interface. PHYSICAL REVIEW LETTERS 2017; 118:106401. [PMID: 28339281 DOI: 10.1103/physrevlett.118.106401] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/10/2016] [Indexed: 06/06/2023]
Abstract
The two-dimensional electron system at the interface between LaAlO_{3} and SrTiO_{3} has several unique properties that can be tuned by an externally applied gate voltage. In this work, we show that this gate tunability extends to the effective band structure of the system. We combine a magnetotransport study on top-gated Hall bars with self-consistent Schrödinger-Poisson calculations and observe a Lifshitz transition at a density of 2.9×10^{13}cm^{-2}. Above the transition, the carrier density of one of the conducting bands decreases with increasing gate voltage. This surprising decrease is accurately reproduced in the calculations if electronic correlations are included. These results provide a clear, intuitive picture of the physics governing the electronic structure at complex-oxide interfaces.
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Affiliation(s)
- A E M Smink
- MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
| | - J C de Boer
- MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
| | - M P Stehno
- MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
| | - A Brinkman
- MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
| | - W G van der Wiel
- MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
| | - H Hilgenkamp
- MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
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13
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Piyanzina II, Kopp T, Lysogorskiy YV, Tayurskii DA, Eyert V. Electronic properties of LaAlO 3/SrTiO 3 n-type interfaces: a GGA+U study. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2017; 29:095501. [PMID: 28067208 DOI: 10.1088/1361-648x/aa57ac] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The role of electronic correlation effects for a realistic description of the electronic properties of [Formula: see text]/[Formula: see text] heterostructures as covered by the on-site Coulomb repulsion within the GGA+U approach is investigated. Performing a systematic variation of the values of the Coulomb parameters applied to the Ti 3d and La 4f orbitals we put previous suggestions to include a large value for the La 4f states into perspective. Furthermore, our calculations provide deeper insight into the band gap landscape in the space spanned by these Coulomb parameters and the resulting complex interference effects. In addition, we identify important correlations between the local Coulomb interaction within the La 4f shell, the band gap, and the atomic displacements at the interface. In particular, these on-site Coulomb interactions influence buckling within the LaO interface layer, which via its strong coupling to the electrostatic potential in the LAO overlayer causes considerable shifts of the electronic states at the surface and eventually controls the band gap.
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Affiliation(s)
- I I Piyanzina
- Institute of Physics, Kazan Federal University, Kremlyovskaya St. 18, 420008 Kazan, Russia. EP VI and Center for Electronic Correlations and Magnetism, Universität Augsburg, Universitätsstraße 1, 86135 Augsburg, Germany
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Atomic-resolved depth profile of strain and cation intermixing around LaAlO3/SrTiO3 interfaces. Sci Rep 2016; 6:28118. [PMID: 27301609 PMCID: PMC4908387 DOI: 10.1038/srep28118] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2016] [Accepted: 05/27/2016] [Indexed: 11/09/2022] Open
Abstract
Novel behavior has been observed at the interface of LaAlO3/SrTiO3 heterostructures such as two dimensional metallic conductivity, magnetic scattering and superconductivity. However, both the origins and quantification of such behavior have been complicated due to an interplay of mechanical, chemical and electronic factors. Here chemical and strain profiles near the interface of LaAlO3/SrTiO3 heterostructures are correlated. Conductive and insulating samples have been processed, with thicknesses respectively above and below the commonly admitted conductivity threshold. The intermixing and structural distortions within the crystal lattice have been quantitatively measured near the interface with a depth resolution of unit cell size. A strong link between intermixing and structural distortions at such interfaces is highlighted: intermixing was more pronounced in the hetero-couple with conductive interface, whereas in-plane compressive strains extended deeper within the substrate of the hetero-couple with the insulating interface. This allows a better understanding of the interface local mechanisms leading to the conductivity.
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