1
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Tuvia G, Burshtein A, Silber I, Aharony A, Entin-Wohlman O, Goldstein M, Dagan Y. Enhanced Nonlinear Response by Manipulating the Dirac Point at the (111) LaTiO_{3}/SrTiO_{3} Interface. PHYSICAL REVIEW LETTERS 2024; 132:146301. [PMID: 38640380 DOI: 10.1103/physrevlett.132.146301] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/23/2023] [Accepted: 03/01/2024] [Indexed: 04/21/2024]
Abstract
Tunable spin-orbit interaction (SOI) is an important feature for future spin-based devices. In the presence of a magnetic field, SOI induces an asymmetry in the energy bands, which can produce nonlinear transport effects (V∼I^{2}). Here, we focus on such effects to study the role of SOI in the (111) LaTiO_{3}/SrTiO_{3} interface. This system is a convenient platform for understanding the role of SOI since it exhibits a single-band Hall response through the entire gate-voltage range studied. We report a pronounced rise in the nonlinear longitudinal resistance at a critical in-plane field H_{cr}. This rise disappears when a small out-of-plane field component is present. We explain these results by considering the location of the Dirac point formed at the crossing of the spin-split energy bands. An in-plane magnetic field pushes this point outside of the Fermi contour, and consequently changes the symmetry of the Fermi contours and intensifies the nonlinear transport. An out-of-plane magnetic field opens a gap at the Dirac point, thereby significantly diminishing the nonlinear effects. We propose that magnetoresistance effects previously reported in interfaces with SOI could be comprehended within our suggested scenario.
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Affiliation(s)
- G Tuvia
- School of Physics and Astronomy, Tel-Aviv University, Tel Aviv 6997801, Israel
| | - A Burshtein
- School of Physics and Astronomy, Tel-Aviv University, Tel Aviv 6997801, Israel
| | - I Silber
- School of Physics and Astronomy, Tel-Aviv University, Tel Aviv 6997801, Israel
| | - A Aharony
- School of Physics and Astronomy, Tel-Aviv University, Tel Aviv 6997801, Israel
| | - O Entin-Wohlman
- School of Physics and Astronomy, Tel-Aviv University, Tel Aviv 6997801, Israel
| | - M Goldstein
- School of Physics and Astronomy, Tel-Aviv University, Tel Aviv 6997801, Israel
| | - Y Dagan
- School of Physics and Astronomy, Tel-Aviv University, Tel Aviv 6997801, Israel
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2
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Eglitis RI, Jia R. Review of Systematic Tendencies in (001), (011) and (111) Surfaces Using B3PW as Well as B3LYP Computations of BaTiO 3, CaTiO 3, PbTiO 3, SrTiO 3, BaZrO 3, CaZrO 3, PbZrO 3 and SrZrO 3 Perovskites. MATERIALS (BASEL, SWITZERLAND) 2023; 16:7623. [PMID: 38138765 PMCID: PMC10745012 DOI: 10.3390/ma16247623] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/20/2023] [Revised: 12/08/2023] [Accepted: 12/11/2023] [Indexed: 12/24/2023]
Abstract
We performed B3PW and B3LYP computations for BaTiO3 (BTO), CaTiO3 (CTO), PbTiO3 (PTO), SrTiO3 (STO), BaZrO3 (BZO), CaZrO3 (CZO), PbZrO3 (PZO) and SrZrO3 (SZO) perovskite neutral (001) along with polar (011) as well as (111) surfaces. For the neutral AO- as well as BO2-terminated (001) surfaces, in most cases, all upper-layer atoms relax inwards, although the second-layer atoms shift outwards. On the (001) BO2-terminated surface, the second-layer metal atoms, as a rule, exhibit larger atomic relaxations than the second-layer O atoms. For most ABO3 perovskites, the (001) surface rumpling s is bigger for the AO- than BO2-terminated surfaces. In contrast, the surface energies, for both (001) terminations, are practically identical. Conversely, different (011) surface terminations exhibit quite different surface energies for the O-terminated, A-terminated and BO-terminated surfaces. Our computed ABO3 perovskite (111) surface energies are always significantly larger than the neutral (001) as well as polar (011) surface energies. Our computed ABO3 perovskite bulk B-O chemical bond covalency increases near their neutral (001) and especially polar (011) surfaces.
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Affiliation(s)
- Roberts I. Eglitis
- Institute of Solid State Physics, University of Latvia, 8 Kengaraga Str., LV1063 Riga, Latvia;
| | - Ran Jia
- Institute of Solid State Physics, University of Latvia, 8 Kengaraga Str., LV1063 Riga, Latvia;
- Laboratory of Theoretical and Computational Chemistry, Institute of Theoretical Chemistry, Jilin University, Changchun 130023, China
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3
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Noh S, Choe D, Jin H, Yoo JW. Enhancement of the Rashba Effect in a Conducting SrTiO 3 Surface by MoO 3 Capping. ACS APPLIED MATERIALS & INTERFACES 2022; 14:50280-50287. [PMID: 36282511 DOI: 10.1021/acsami.2c11840] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Systems having inherent structural asymmetry retain the Rashba-type spin-orbit interaction, which ties the spin and momentum of electrons in the band structure, leading to coupled spin and charge transport. One of the electrical manifestations of the Rashba spin-orbit interaction is nonreciprocal charge transport, which could be utilized for rectifying devices. Further tuning of the Rashba spin-orbit interaction allows additional functionalities in spin-orbitronic applications. In this work, we present our study of nonreciprocal charge transport in a conducting SrTiO3 (001) surface and its significant enhancement by a capping layer. The conductive strontium titanate SrTiO3 (STO) (001) surface was created through oxygen vacancies by Ar+ irradiation, and the nonreciprocal signal was probed by angle- and magnetic field-dependent second harmonic voltage measurement with an AC current. We observed robust directional transport in the Ar+-irradiated sample at low temperatures. The magnitude of the nonreciprocal signal is highly dependent on the irradiation time as it affects the depth of the conducting layer and the impact of the topmost conducting layer. Moreover, the nonreciprocal resistance was significantly enhanced by simply adding a MoO3 capping layer on the conductive STO surface. These results show a simple methodology for tuning and investigating the Rashba effect in a conductive STO surface, which could be adopted for various two-dimensional (2D) conducting layers for spin-orbitronic applications.
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Affiliation(s)
- Seunghyeon Noh
- Department of Materials Science and Engineering, Ulsan National Institute of Science and Technology, Ulsan44919, Korea
| | - Daeseong Choe
- Department of Materials Science and Engineering, Ulsan National Institute of Science and Technology, Ulsan44919, Korea
| | - Hosub Jin
- Department of Physics, Ulsan National Institute of Science and Technology, Ulsan44919, Korea
| | - Jung-Woo Yoo
- Department of Materials Science and Engineering, Ulsan National Institute of Science and Technology, Ulsan44919, Korea
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4
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Varotto S, Johansson A, Göbel B, Vicente-Arche LM, Mallik S, Bréhin J, Salazar R, Bertran F, Fèvre PL, Bergeal N, Rault J, Mertig I, Bibes M. Direct visualization of Rashba-split bands and spin/orbital-charge interconversion at KTaO 3 interfaces. Nat Commun 2022; 13:6165. [PMID: 36257940 PMCID: PMC9579156 DOI: 10.1038/s41467-022-33621-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2022] [Accepted: 09/23/2022] [Indexed: 11/25/2022] Open
Abstract
Rashba interfaces have emerged as promising platforms for spin-charge interconversion through the direct and inverse Edelstein effects. Notably, oxide-based two-dimensional electron gases display a large and gate-tunable conversion efficiency, as determined by transport measurements. However, a direct visualization of the Rashba-split bands in oxide two-dimensional electron gases is lacking, which hampers an advanced understanding of their rich spin-orbit physics. Here, we investigate KTaO3 two-dimensional electron gases and evidence their Rashba-split bands using angle resolved photoemission spectroscopy. Fitting the bands with a tight-binding Hamiltonian, we extract the effective Rashba coefficient and bring insight into the complex multiorbital nature of the band structure. Our calculations reveal unconventional spin and orbital textures, showing compensation effects from quasi-degenerate band pairs which strongly depend on in-plane anisotropy. We compute the band-resolved spin and orbital Edelstein effects, and predict interconversion efficiencies exceeding those of other oxide two-dimensional electron gases. Finally, we suggest design rules for Rashba systems to optimize spin-charge interconversion performance. Visualization of the Rashbasplit bands in oxide two-dimensional electron gases is lacking, which hampers understanding of their rich spin-orbit physics. Here, the authors investigate KTaO3 two dimensional electron gases and their Rashba-split bands.
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Affiliation(s)
- Sara Varotto
- Unité Mixte de Physique, CNRS, Thales, Université Paris-Saclay, 91767, Palaiseau, France
| | - Annika Johansson
- Max Planck Institute of Microstructure Physics, Weinberg 2, 06120, Halle, Germany.
| | - Börge Göbel
- Institute of Physics, Martin-Luther-Universität Halle-Wittenberg, 06099, Halle, Germany
| | - Luis M Vicente-Arche
- Unité Mixte de Physique, CNRS, Thales, Université Paris-Saclay, 91767, Palaiseau, France
| | - Srijani Mallik
- Unité Mixte de Physique, CNRS, Thales, Université Paris-Saclay, 91767, Palaiseau, France
| | - Julien Bréhin
- Unité Mixte de Physique, CNRS, Thales, Université Paris-Saclay, 91767, Palaiseau, France
| | - Raphaël Salazar
- Synchrotron SOLEIL, L'Orme des Merisiers, Saint-Aubin, BP 48, Gif-sur-Yvette Cedex, 91192, France
| | - François Bertran
- Synchrotron SOLEIL, L'Orme des Merisiers, Saint-Aubin, BP 48, Gif-sur-Yvette Cedex, 91192, France
| | - Patrick Le Fèvre
- Synchrotron SOLEIL, L'Orme des Merisiers, Saint-Aubin, BP 48, Gif-sur-Yvette Cedex, 91192, France
| | - Nicolas Bergeal
- Laboratoire de Physique et d'Etude des Matériaux, ESPCI Paris, Université PSL, CNRS, 75005, Paris, France
| | - Julien Rault
- Synchrotron SOLEIL, L'Orme des Merisiers, Saint-Aubin, BP 48, Gif-sur-Yvette Cedex, 91192, France
| | - Ingrid Mertig
- Institute of Physics, Martin-Luther-Universität Halle-Wittenberg, 06099, Halle, Germany
| | - Manuel Bibes
- Unité Mixte de Physique, CNRS, Thales, Université Paris-Saclay, 91767, Palaiseau, France.
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Lafalce E, Amerling E, Yu ZG, Sercel PC, Whittaker-Brooks L, Vardeny ZV. Rashba splitting in organic-inorganic lead-halide perovskites revealed through two-photon absorption spectroscopy. Nat Commun 2022; 13:483. [PMID: 35078984 PMCID: PMC8789784 DOI: 10.1038/s41467-022-28127-9] [Citation(s) in RCA: 19] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2020] [Accepted: 01/10/2022] [Indexed: 11/30/2022] Open
Abstract
The Rashba splitting in hybrid organic-inorganic lead-halide perovskites (HOIP) is particularly promising and yet controversial, due to questions surrounding the presence or absence of inversion symmetry. Here we utilize two-photon absorption spectroscopy to study inversion symmetry breaking in different phases of these materials. This is an all-optical technique to observe and quantify the Rashba effect as it probes the bulk of the materials. In particular, we measure two-photon excitation spectra of the photoluminescence in 2D, 3D, and anionic mixed HOIP crystals, and show that an additional band above, but close to the optical gap is the signature of new two-photon transition channels that originate from the Rashba splitting. The inversion symmetry breaking is believed to arise from ionic impurities that induce local electric fields. The observation of the Rashba splitting in the bulk of HOIP has significant implications for the understanding of their spintronic and optoelectronic device properties.
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Affiliation(s)
- Evan Lafalce
- Department of Physics & Astronomy, University of Utah, Salt Lake City, UT, 84112, USA
| | - Eric Amerling
- Department of Chemistry, University of Utah, Salt Lake City, UT, 84112, USA
| | - Zhi-Gang Yu
- Sivananthan Laboratories, Bolingbrook, IL, 60440, USA
| | - Peter C Sercel
- Center for Hybrid Organic Inorganic Semiconductors for Energy, 15013 Denver West Parkway, Golden, CO, 80401, USA
| | | | - Z Valy Vardeny
- Department of Physics & Astronomy, University of Utah, Salt Lake City, UT, 84112, USA.
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6
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Guedes EB, Muff S, Brito WH, Caputo M, Li H, Plumb NC, Dil JH, Radović M. Universal Structural Influence on the 2D Electron Gas at SrTiO 3 Surfaces. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2021; 8:e2100602. [PMID: 34532983 PMCID: PMC8596100 DOI: 10.1002/advs.202100602] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/16/2021] [Revised: 06/23/2021] [Indexed: 05/28/2023]
Abstract
The 2-dimensional electron gas (2DEG) found at the surface of SrTiO3 and related interfaces has attracted significant attention as a promising basis for oxide electronics. In order to utilize its full potential, the response of this 2DEG to structural changes and surface modification must be understood in detail. Here, a study of the detailed electronic structure evolution of the 2DEG as a function of sample temperature and surface step density is presented. By comparing the experimental results with ab initio calculations, it is shown that local structure relaxations cause a metal-insulator transition of the system around 135 K. This study presents a new and simple way of tuning the 2DEG via surface vicinality and identifies how the operation of prospective devices will respond to changes in temperature.
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Affiliation(s)
- Eduardo B. Guedes
- Photon Science DivisionPaul Scherrer InstitutVilligenCH‐5232Switzerland
| | - Stefan Muff
- Photon Science DivisionPaul Scherrer InstitutVilligenCH‐5232Switzerland
| | - Walber H. Brito
- Departamento de FísicaUniversidade Federal de Minas GeraisC.P. 702Belo HorizonteMinas Gerais30123Brazil
| | - Marco Caputo
- Photon Science DivisionPaul Scherrer InstitutVilligenCH‐5232Switzerland
- Elettra‐Sincrotrone TriesteS.C.p.A, S.S 14‐km 163.5 in AREA Science Park, BasovizzaTrieste34149Italy
| | - Hang Li
- Photon Science DivisionPaul Scherrer InstitutVilligenCH‐5232Switzerland
- Department of Energy Conversion and StorageTechnical University of DenmarkKgs. Lyngby2800Denmark
| | - Nicholas C. Plumb
- Photon Science DivisionPaul Scherrer InstitutVilligenCH‐5232Switzerland
| | - J. Hugo Dil
- Photon Science DivisionPaul Scherrer InstitutVilligenCH‐5232Switzerland
- Institut de PhysiqueÉcole Polytechnique Fédérale de LausanneLausanneCH‐1015Switzerland
| | - Milan Radović
- Photon Science DivisionPaul Scherrer InstitutVilligenCH‐5232Switzerland
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7
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Ricciardulli AG, Yang S, Smet JH, Saliba M. Emerging perovskite monolayers. NATURE MATERIALS 2021; 20:1325-1336. [PMID: 34112976 DOI: 10.1038/s41563-021-01029-9] [Citation(s) in RCA: 52] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/22/2020] [Accepted: 04/28/2021] [Indexed: 05/26/2023]
Abstract
The library of two-dimensional (2D) materials has been enriched over recent years with novel crystal architectures endowed with diverse exciting functionalities. Bulk perovskites, including metal-halide and oxide systems, provide access to a myriad of properties through molecular engineering. Their tunable electronic structure offers remarkable features from long carrier-diffusion lengths and high absorption coefficients in metal-halide perovskites to high-temperature superconductivity, magnetoresistance and ferroelectricity in oxide perovskites. Emboldened by the 2D materials research, perovskites down to the monolayer limit have recently emerged. Like other 2D species, perovskites with reduced dimensionality are expected to exhibit new physics and to herald next-generation multifunctional devices. In this Review, we critically assess the preliminary studies on the synthetic routes and inherent properties of monolayer perovskite materials. We also discuss how to exploit them for widespread applications and provide an outlook on the challenges and opportunities that lie ahead for this enticing class of 2D materials.
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Affiliation(s)
- Antonio Gaetano Ricciardulli
- Technical University of Darmstadt, Darmstadt, Germany
- Université de Strasbourg, CNRS, ISIS UMR 7006, Strasbourg, France
| | - Sheng Yang
- Max Planck Institute for Solid State Research, Stuttgart, Germany.
| | - Jurgen H Smet
- Max Planck Institute for Solid State Research, Stuttgart, Germany.
| | - Michael Saliba
- Technical University of Darmstadt, Darmstadt, Germany.
- Institute for Photovoltaics, University of Stuttgart, Stuttgart, Germany.
- Helmholtz Young Investigator Group FRONTRUNNER, Forschungszentrum Jülich, Jülich, Germany.
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8
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Jin MJ, Um DS, Ohnishi K, Komori S, Stelmashenko N, Choe D, Yoo JW, Robinson JWA. Pure Spin Currents Driven by Colossal Spin-Orbit Coupling on Two-Dimensional Surface Conducting SrTiO 3. NANO LETTERS 2021; 21:6511-6517. [PMID: 34320314 DOI: 10.1021/acs.nanolett.1c01607] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Spin accumulation is generated by passing a charge current through a ferromagnetic layer and sensed by other ferromagnetic layers downstream. Pure spin currents can also be generated in which spin currents flow and are detected as a nonlocal resistance in which the charge current is diverted away from the voltage measurement point. Here, we report nonlocal spin-transport on two-dimensional surface-conducting SrTiO3 (STO) without a ferromagnetic spin-injector via the spin Hall effect (and inverse spin Hall effect). By applying magnetic fields to the Hall bars at different angles to the nonlocal spin-diffusion, we demonstrate an anisotropic spin-signal that is consistent with a Hanle precession of a pure spin current. We extract key transport parameters for surface-conducting STO, including: a spin Hall angle of γ ≈ (0.25 ± 0.05), a spin lifetime of τ ∼ 49 ps, and a spin diffusion length of λs ≈ (1.23 ± 0.7) μm at 2 K.
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Affiliation(s)
- Mi-Jin Jin
- Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS, United Kingdom
| | - Doo-Seung Um
- Department of Electrical Engineering, Sejong University, Seoul 05006, Republic of Korea
| | - Kohei Ohnishi
- Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS, United Kingdom
- Department of Physics, Kyushu University, 744 Motooka, Fukuoka 819-0395, Japan
| | - Sachio Komori
- Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS, United Kingdom
| | - Nadia Stelmashenko
- Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS, United Kingdom
| | - Daeseong Choe
- School of Materials Science and Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan, 44919, Republic of Korea
| | - Jung-Woo Yoo
- School of Materials Science and Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan, 44919, Republic of Korea
| | - Jason W A Robinson
- Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS, United Kingdom
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9
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Kataoka N, Tanaka M, Hosoda W, Taniguchi T, Fujimori SI, Wakita T, Muraoka Y, Yokoya T. Soft x-ray irradiation induced metallization of layered TiNCl. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2020; 33:035501. [PMID: 32977314 DOI: 10.1088/1361-648x/abbbc3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/11/2020] [Accepted: 09/25/2020] [Indexed: 06/11/2023]
Abstract
We have performed soft x-ray spectroscopy in order to study the photoirradiation time dependence of the valence band structure and chemical states of layered transition metal nitride chloride TiNCl. Under the soft x-ray irradiation, the intensities of the states near the Fermi level (EF) and the Ti3+component increased, while the Cl 2pintensity decreased. Ti 2p-3dresonance photoemission spectroscopy confirmed a distinctive Fermi edge with Ti 3dcharacter. These results indicate the photo-induced metallization originates from deintercalation due to Cl desorption, and thus provide a new carrier doping method that controls the conducting properties of TiNCl.
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Affiliation(s)
- Noriyuki Kataoka
- Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan
| | - Masashi Tanaka
- Graduate School of Engineering, Kyushu Institute of Technology, Kitakyushu 804-8550, Japan
| | - Wataru Hosoda
- Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan
| | - Takumi Taniguchi
- Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan
| | - Shin-Ichi Fujimori
- Materials Sciences Research Center, Japan Atomic Energy Agency, Sayo, Hyogo 679-5148, Japan
| | - Takanori Wakita
- Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan
- Research Institute for Interdisciplinary Science, Okayama University, Okayama 700-8530, Japan
| | - Yuji Muraoka
- Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan
- Research Institute for Interdisciplinary Science, Okayama University, Okayama 700-8530, Japan
| | - Takayoshi Yokoya
- Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan
- Research Institute for Interdisciplinary Science, Okayama University, Okayama 700-8530, Japan
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10
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Giant Zeeman-type spin splitting of free electron/hole states on quasi-2D perovskite niobates: a theoretical prediction. Sci Rep 2020; 10:3698. [PMID: 32111910 PMCID: PMC7048772 DOI: 10.1038/s41598-020-60653-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2019] [Accepted: 02/17/2020] [Indexed: 11/08/2022] Open
Abstract
We study the spin-orbit interaction of two-dimensional electron/hole gas (2DEGs/2DHGs) on quasi-2D potassium niobates (KNs) via first-principles calculations. The strong surface polarity changes the free surface states from 2DEGs to 2DHGs. The in-plane dipole maintained on 2D models leads to giant Zeeman-type spin splitting, as high as 566 meV for the (001)c facet KN and 1.21 eV for the (111)c facet KN. The thickness-dependent Zeeman-type spin splitting shows a linear relation with respect to 1/r, while the corresponding in-plane polarization quantum has a linear relation of 1/(2^0.5)with respect to a decrease in thickness. Interestingly, the 2DHGs with molecular-like orbital character is solely constituted by O 2p states, showing logic switchable behavior at extremely thin samples with enormous Zeeman-type splitting that can switch between insulator and conductor by opposite spin polarization.
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11
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Wadehra N, Tomar R, Varma RM, Gopal RK, Singh Y, Dattagupta S, Chakraverty S. Planar Hall effect and anisotropic magnetoresistance in polar-polar interface of LaVO 3-KTaO 3 with strong spin-orbit coupling. Nat Commun 2020; 11:874. [PMID: 32054860 PMCID: PMC7018836 DOI: 10.1038/s41467-020-14689-z] [Citation(s) in RCA: 47] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2019] [Accepted: 01/23/2020] [Indexed: 11/26/2022] Open
Abstract
Among the perovskite oxide family, KTaO3 (KTO) has recently attracted considerable interest as a possible system for the realization of the Rashba effect. In this work, we report a novel conducting interface by placing KTO with another insulator, LaVO3 (LVO) and report planar Hall effect (PHE) and anisotropic magnetoresistance (AMR) measurements. This interface exhibits a signature of strong spin-orbit coupling. Our experimental observations of two fold AMR and PHE at low magnetic fields (B) is similar to those obtained for topological systems and can be intuitively understood using a phenomenological theory for a Rashba spin-split system. Our experimental data show a B2 dependence of AMR and PHE at low magnetic fields that could also be explained based on our model. At high fields (~8 T), we see a two fold to four fold transition in the AMR that could not be explained using only Rashba spin-split energy spectra. Two dimensional electron gas (2DEG) at oxide interfaces is promising in modern electronic devices. Here, Wadehra et al. realize 2DEG at a novel interface composed of LaVO3 and KTaO3, where strong spin-orbit coupling and relativistic nature of the electrons in the 2DEG, leading to anisotropic magnetoresistance and planar Hall effect.
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Affiliation(s)
- Neha Wadehra
- Nanoscale Physics and Device Laboratory, Institute of Nano Science and Technology, Phase-10, Sector-64, Mohali, Punjab, 160062, India
| | - Ruchi Tomar
- Nanoscale Physics and Device Laboratory, Institute of Nano Science and Technology, Phase-10, Sector-64, Mohali, Punjab, 160062, India
| | - Rahul Mahavir Varma
- Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangaluru, Karnataka, 560012, India
| | - R K Gopal
- Indian Institute of Science Education and Research Mohali, Knowledge City, Sector-81, SAS Nagar, Manauli, 140306, India
| | - Yogesh Singh
- Indian Institute of Science Education and Research Mohali, Knowledge City, Sector-81, SAS Nagar, Manauli, 140306, India
| | - Sushanta Dattagupta
- Bose Institute, P-1/12, CIT Rd, Scheme VIIM, Kankurgachi, Kolkata, West Bengal, 700054, India
| | - S Chakraverty
- Nanoscale Physics and Device Laboratory, Institute of Nano Science and Technology, Phase-10, Sector-64, Mohali, Punjab, 160062, India.
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12
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Mori R, Marshall PB, Ahadi K, Denlinger JD, Stemmer S, Lanzara A. Controlling a Van Hove singularity and Fermi surface topology at a complex oxide heterostructure interface. Nat Commun 2019; 10:5534. [PMID: 31797932 PMCID: PMC6892806 DOI: 10.1038/s41467-019-13046-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2018] [Accepted: 10/16/2019] [Indexed: 11/10/2022] Open
Abstract
The emergence of saddle-point Van Hove singularities (VHSs) in the density of states, accompanied by a change in Fermi surface topology, Lifshitz transition, constitutes an ideal ground for the emergence of different electronic phenomena, such as superconductivity, pseudo-gap, magnetism, and density waves. However, in most materials the Fermi level, \documentclass[12pt]{minimal}
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\begin{document}$${E}_{{\rm{F}}}$$\end{document}EF, is too far from the VHS where the change of electronic topology takes place, making it difficult to reach with standard chemical doping or gating techniques. Here, we demonstrate that this scenario can be realized at the interface between a Mott insulator and a band insulator as a result of quantum confinement and correlation enhancement, and easily tuned by fine control of layer thickness and orbital occupancy. These results provide a tunable pathway for Fermi surface topology and VHS engineering of electronic phases. A singularity in a material’s density of states at the Fermi energy can drive the formation of unconventional electronic phases. Here the authors show a Van Hove singularity is tunable across the Fermi energy in an oxide heterostructure, leading to enhanced electronic correlations.
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Affiliation(s)
- Ryo Mori
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA.,Applied Science & Technology, University of California, Berkeley, CA, 94720, USA
| | - Patrick B Marshall
- Materials Department, University of California, Santa Barbara, CA, 93106-5050, USA
| | - Kaveh Ahadi
- Materials Department, University of California, Santa Barbara, CA, 93106-5050, USA
| | - Jonathan D Denlinger
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
| | - Susanne Stemmer
- Materials Department, University of California, Santa Barbara, CA, 93106-5050, USA
| | - Alessandra Lanzara
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA. .,Department of Physics, University of California, Berkeley, CA, 94720, USA.
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13
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Aiura Y, Ozawa K, Tezuka Y, Minohara M, Samizo A, Bando K, Kumigashira H, Mase K. In-gap state generated by La-on-Sr substitutional defects within the bulk of SrTiO 3. Phys Chem Chem Phys 2019; 21:14646-14653. [PMID: 31215560 DOI: 10.1039/c9cp02307k] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Local distortion in the conduction pathway has a significant influence on the conducting properties of oxides. The electronic states induced in the band gap of SrTiO3 by La doping were investigated using photoemission spectroscopy (PES) and soft X-ray emission spectroscopy (SXES); moreover, the local distortion in the conduction pathway was examined using extended X-ray absorption fine structure (EXAFS). An itinerant state and a localized state were observed as a metallic state and an in-gap state, respectively, in the PES spectra and as inelastic peaks in the SXES spectra. This implied that the itinerant state and the in-gap state coexisted within the bulk. From EXAFS results, it was observed that La doped into SrTiO3 substituted Sr and locally distorted the conduction pathway. The results showed that some electrons doped by La-on-Sr substitution are trapped/localized by the local distortion in the conduction pathway, whereas the remaining doped electrons itinerate in the pristine conduction pathway with no distortion.
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Affiliation(s)
- Yoshihiro Aiura
- Electronics and Photonics Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki 305-8568, Japan.
| | - Kenichi Ozawa
- Department of Chemistry, Tokyo Institute of Technology, Meguro, Tokyo 152-8551, Japan
| | - Yasuhisa Tezuka
- Graduate School of Science and Technology, Hirosaki University, Hirosaki, Aomori 036-8561, Japan
| | - Makoto Minohara
- Electronics and Photonics Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki 305-8568, Japan.
| | - Akane Samizo
- Electronics and Photonics Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki 305-8568, Japan. and Department of Materials Science and Technology, Faculty of Industrial Science and Technology, Tokyo University of Science, Katsushika, Tokyo 125-8585, Japan
| | - Kyoko Bando
- Nanomaterials Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki 305-8565, Japan
| | - Hiroshi Kumigashira
- Photon Factory, Institute of Materials Structure Science (IMSS), High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki 305-0801, Japan and Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai 980-8578, Japan
| | - Kazuhiko Mase
- Photon Factory, Institute of Materials Structure Science (IMSS), High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki 305-0801, Japan and SOKENDAI (The Graduate University for Advanced Studies), Tsukuba, Ibaraki 305-0801, Japan
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14
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He P, Zhang SSL, Zhu D, Shi S, Heinonen OG, Vignale G, Yang H. Nonlinear Planar Hall Effect. PHYSICAL REVIEW LETTERS 2019; 123:016801. [PMID: 31386424 DOI: 10.1103/physrevlett.123.016801] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/12/2018] [Revised: 05/07/2019] [Indexed: 06/10/2023]
Abstract
An intriguing property of a three-dimensional (3D) topological insulator (TI) is the existence of surface states with spin-momentum locking, which offers a new frontier of exploration in spintronics. Here, we report the observation of a new type of Hall effect in a 3D TI Bi_{2}Se_{3} film. The Hall resistance scales linearly with both the applied electric and magnetic fields and exhibits a π/2 angle offset with respect to its longitudinal counterpart, in contrast to the usual angle offset of π/4 between the linear planar Hall effect and the anisotropic magnetoresistance. This novel nonlinear planar Hall effect originates from the conversion of a nonlinear transverse spin current to a charge current due to the concerted actions of spin-momentum locking and time-reversal symmetry breaking, which also exists in a wide class of noncentrosymmetric materials with a large span of magnitude. It provides a new way to characterize and utilize the nonlinear spin-to-charge conversion in a variety of topological quantum materials.
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Affiliation(s)
- Pan He
- Department of Electrical and Computer Engineering, and NUSNNI, National University of Singapore, 117576 Singapore
| | - Steven S-L Zhang
- Materials Science Division, Argonne National Laboratory, Lemont, Illinois 60439, USA
- Department of Physics and Astronomy, University of Missouri, Columbia, Missouri 65211, USA
| | - Dapeng Zhu
- Department of Electrical and Computer Engineering, and NUSNNI, National University of Singapore, 117576 Singapore
| | - Shuyuan Shi
- Department of Electrical and Computer Engineering, and NUSNNI, National University of Singapore, 117576 Singapore
| | - Olle G Heinonen
- Materials Science Division, Argonne National Laboratory, Lemont, Illinois 60439, USA
| | - Giovanni Vignale
- Department of Physics and Astronomy, University of Missouri, Columbia, Missouri 65211, USA
| | - Hyunsoo Yang
- Department of Electrical and Computer Engineering, and NUSNNI, National University of Singapore, 117576 Singapore
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15
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Gan Y, Christensen DV, Zhang Y, Zhang H, Krishnan D, Zhong Z, Niu W, Carrad DJ, Norrman K, von Soosten M, Jespersen TS, Shen B, Gauquelin N, Verbeeck J, Sun J, Pryds N, Chen Y. Diluted Oxide Interfaces with Tunable Ground States. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2019; 31:e1805970. [PMID: 30637817 DOI: 10.1002/adma.201805970] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/13/2018] [Revised: 12/31/2018] [Indexed: 06/09/2023]
Abstract
The metallic interface between two oxide insulators, such as LaAlO3 /SrTiO3 (LAO/STO), provides new opportunities for electronics and spintronics. However, due to the presence of multiple orbital populations, tailoring the interfacial properties such as the ground state and metal-insulator transitions remains challenging. Here, an unforeseen tunability of the phase diagram of LAO/STO is reported by alloying LAO with a ferromagnetic LaMnO3 insulator without forming lattice disorder and at the same time without changing the polarity of the system. By increasing the Mn-doping level, x, of LaAl1- x Mnx O3 /STO (0 ≤ x ≤ 1), the interface undergoes a Lifshitz transition at x = 0.225 across a critical carrier density of nc = 2.8 × 1013 cm-2 , where a peak TSC ≈255 mK of superconducting transition temperature is observed. Moreover, the LaAl1- x Mnx O3 turns ferromagnetic at x ≥ 0.25. Remarkably, at x = 0.3, where the metallic interface is populated by only dxy electrons and just before it becomes insulating, a same device with both signatures of superconductivity and clear anomalous Hall effect (7.6 × 1012 cm-2 < ns ≤ 1.1 × 1013 cm-2 ) is achieved reproducibly. This provides a unique and effective way to tailor oxide interfaces for designing on-demand electronic and spintronic devices.
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Affiliation(s)
- Yulin Gan
- Department of Energy Conversion and Storage, Technical University of Denmark, Risø Campus, 4000, Roskilde, Denmark
| | - Dennis Valbjørn Christensen
- Department of Energy Conversion and Storage, Technical University of Denmark, Risø Campus, 4000, Roskilde, Denmark
| | - Yu Zhang
- Department of Energy Conversion and Storage, Technical University of Denmark, Risø Campus, 4000, Roskilde, Denmark
- National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
| | - Hongrui Zhang
- National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
| | - Dileep Krishnan
- EMAT, University of Antwerp, Groenenborgerlaan 171, 2020, Antwerp, Belgium
| | - Zhicheng Zhong
- Key Laboratory of Magnetic Materials and Devices, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo, 315201, China
| | - Wei Niu
- Department of Energy Conversion and Storage, Technical University of Denmark, Risø Campus, 4000, Roskilde, Denmark
| | - Damon James Carrad
- Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, 2100, Copenhagen, Denmark
| | - Kion Norrman
- Department of Energy Conversion and Storage, Technical University of Denmark, Risø Campus, 4000, Roskilde, Denmark
| | - Merlin von Soosten
- Department of Energy Conversion and Storage, Technical University of Denmark, Risø Campus, 4000, Roskilde, Denmark
- Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, 2100, Copenhagen, Denmark
| | - Thomas Sand Jespersen
- Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, 2100, Copenhagen, Denmark
| | - Baogen Shen
- National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
| | - Nicolas Gauquelin
- EMAT, University of Antwerp, Groenenborgerlaan 171, 2020, Antwerp, Belgium
| | - Johan Verbeeck
- EMAT, University of Antwerp, Groenenborgerlaan 171, 2020, Antwerp, Belgium
| | - Jirong Sun
- National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
| | - Nini Pryds
- Department of Energy Conversion and Storage, Technical University of Denmark, Risø Campus, 4000, Roskilde, Denmark
| | - Yunzhong Chen
- Department of Energy Conversion and Storage, Technical University of Denmark, Risø Campus, 4000, Roskilde, Denmark
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16
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Gariglio S, Caviglia AD, Triscone JM, Gabay M. A spin-orbit playground: surfaces and interfaces of transition metal oxides. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2019; 82:012501. [PMID: 30058557 DOI: 10.1088/1361-6633/aad6ab] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Within the last twenty years, the status of the spin-orbit interaction has evolved from that of a simple atomic contribution to a key effect that modifies the electronic band structure of materials. It is regarded as one of the basic ingredients for spintronics, locking together charge and spin degrees of freedom and recently it is instrumental in promoting a new class of compounds, the topological insulators. In this review, we present the current status of the research on the spin-orbit coupling in transition metal oxides, discussing the case of two semiconducting compounds, [Formula: see text] and [Formula: see text], and the properties of surface and interfaces based on these. We conclude with the investigation of topological effects predicted to occur in different complex oxides.
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Affiliation(s)
- S Gariglio
- DQMP, University of Geneva, 24 Quai E.-Ansermet 1211, Geneva, Switzerland
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17
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First-principles Study of Rashba Spin Splitting at Strained SrTiO<sub>3</sub>(001) Surfaces. E-JOURNAL OF SURFACE SCIENCE AND NANOTECHNOLOGY 2018. [DOI: 10.1380/ejssnt.2018.360] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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18
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Mechanical dissipation from charge and spin transitions in oxygen-deficient SrTiO 3 surfaces. Nat Commun 2018; 9:2946. [PMID: 30054477 PMCID: PMC6063934 DOI: 10.1038/s41467-018-05392-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2018] [Accepted: 06/26/2018] [Indexed: 11/15/2022] Open
Abstract
Bodies in relative motion separated by a gap of a few nanometers can experience a tiny friction force. This non-contact dissipation can have various origins and can be successfully measured by a sensitive pendulum atomic force microscope tip oscillating laterally above the surface. Here, we report on the observation of dissipation peaks at selected voltage-dependent tip-surface distances for oxygen-deficient strontium titanate (SrTiO3) surface at low temperatures (T = 5 K). The observed dissipation peaks are attributed to tip-induced charge and spin state transitions in quantum-dot-like entities formed by single oxygen vacancies (and clusters thereof, possibly through a collective mechanism) at the SrTiO3 surface, which in view of technological and fundamental research relevance of the material opens important avenues for further studies and applications. Non-contact atomic force microscope (AFM) dissipation contains rich information on the electron, phonon and spin states, but has been poorly understood. Here the authors demonstrated that tip-induced charge and spin state transitions in oxygen vacancies at SrTiO3 surface are revealed by AFM dissipation measurements.
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19
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Chen X, Liu L, Shen D. n-type Rashba spin splitting in a bilayer inorganic halide perovskite with external electric field. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2018; 30:265501. [PMID: 29766906 DOI: 10.1088/1361-648x/aac523] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Here, we investigated the Rashba effect of the CsPbBr3 bilayers under the external electric field (EEF) with first-principles calculations. For the PbBr2 terminated bilayer, we found that only electrons experience the Rashba splitting under EEF, while holes do not. Such an n-type Rashba effect can be ascribed to the surface relaxation effect that reverses the positions of the top valence bands. The n-type Rashba parameter can be tuned monotonically to the maximum of 0.88 eV Å at EEF of 1.35 V nm-1 at which the sequence of top valence bands recover to the bulk style. During this process the p-type spins will not survive in this 2D CsPbBr3, that indeed reveals a new way for making advanced functional spintronic devices.
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Affiliation(s)
- Xuejiao Chen
- State Key Laboratory of Luminescence and Applications, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, No.3888 Dongnanhu Road, Changchun 130033, People's Republic of China. University of Chinese Academy of Sciences, Beijing 100049, People's Republic of China
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20
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Veit MJ, Arras R, Ramshaw BJ, Pentcheva R, Suzuki Y. Nonzero Berry phase in quantum oscillations from giant Rashba-type spin splitting in LaTiO 3/SrTiO 3 heterostructures. Nat Commun 2018; 9:1458. [PMID: 29654231 PMCID: PMC5899139 DOI: 10.1038/s41467-018-04014-0] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2017] [Accepted: 03/26/2018] [Indexed: 11/17/2022] Open
Abstract
The manipulation of the spin degrees of freedom in a solid has been of fundamental and technological interest recently for developing high-speed, low-power computational devices. There has been much work focused on developing highly spin-polarized materials and understanding their behavior when incorporated into so-called spintronic devices. These devices usually require spin splitting with magnetic fields. However, there is another promising strategy to achieve spin splitting using spatial symmetry breaking without the use of a magnetic field, known as Rashba-type splitting. Here we report evidence for a giant Rashba-type splitting at the interface of LaTiO3 and SrTiO3. Analysis of the magnetotransport reveals anisotropic magnetoresistance, weak anti-localization and quantum oscillation behavior consistent with a large Rashba-type splitting. It is surprising to find a large Rashba-type splitting in 3d transition metal oxide-based systems such as the LaTiO3/SrTiO3 interface, but it is promising for the development of a new kind of oxide-based spintronics. Rashba-type splitting is an effective way to manipulate the spin degrees of freedom in a solid without external magnetic field. Here, the authors demonstrate a strong Rashba-type splitting at the interface of LaTiO3 and SrTiO3 which is promising for the development of oxide-based spintronics.
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Affiliation(s)
- M J Veit
- Department of Applied Physics and Geballe Laboratory for Advanced Materials, Stanford University, Stanford, CA, 94305, USA.
| | - R Arras
- CEMES, University of Toulouse, CNRS, UPS, 29, rue Jeanne Marvig, 31055, Toulouse, France
| | - B J Ramshaw
- Los Alamos National Laboratory, Los Alamos, NM, 87545, USA.,Laboratory for Atomic and Solid State Physics, Cornell University, Ithaca, NY, 14853, USA
| | - R Pentcheva
- Department of Physics and Center for Nanointegration (CENIDE), University of Duisburg-Essen, Lotharstrasse 1, 47057, Duisburg, Germany
| | - Y Suzuki
- Department of Applied Physics and Geballe Laboratory for Advanced Materials, Stanford University, Stanford, CA, 94305, USA
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21
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Qiu X, Shi Z, Fan W, Zhou S, Yang H. Characterization and Manipulation of Spin Orbit Torque in Magnetic Heterostructures. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2018; 30:e1705699. [PMID: 29468735 DOI: 10.1002/adma.201705699] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/30/2017] [Revised: 11/01/2017] [Indexed: 06/08/2023]
Abstract
Electrical-current-induced magnetization switching is a keystone concept in the development of spintronics devices. In the last few years, this field has experienced a significant boost with the discovery of spin orbit torque (SOT) in magnetic heterostructures. Here, the recent results as to the characterization and manipulation of SOT in various heavy-metal/ferromagnet heterostructures are summarized. First, different electrical measurement methods that allow the physical features of SOT to be revealed are introduced. Second, it is shown that SOT in magnetic heterostructures can be manipulated via various material engineering approaches. The interfacial and bulk contributions of SOT are also discussed. These results advance the understanding of SOT and provide novel approaches toward energy-efficient spintronic devices.
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Affiliation(s)
- Xuepeng Qiu
- Shanghai Key Laboratory of Special Artificial Microstructure Materials and Technology and School of Physics Science and Engineering, Tongji University, Shanghai, 200092, China
| | - Zhong Shi
- Shanghai Key Laboratory of Special Artificial Microstructure Materials and Technology and School of Physics Science and Engineering, Tongji University, Shanghai, 200092, China
| | - Weijia Fan
- Shanghai Key Laboratory of Special Artificial Microstructure Materials and Technology and School of Physics Science and Engineering, Tongji University, Shanghai, 200092, China
| | - Shiming Zhou
- Shanghai Key Laboratory of Special Artificial Microstructure Materials and Technology and School of Physics Science and Engineering, Tongji University, Shanghai, 200092, China
| | - Hyunsoo Yang
- Department of Electrical and Computer Engineering, National University of Singapore, Singapore, 117576, Singapore
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22
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Zhang Y, Xie L, Kim J, Stern A, Wang H, Zhang K, Yan X, Li L, Liu H, Zhao G, Chi H, Gadre C, Lin Q, Zhou Y, Uher C, Chen T, Chu YH, Xia J, Wu R, Pan X. Discovery of a magnetic conductive interface in PbZr 0.2Ti 0.8O 3 /SrTiO 3 heterostructures. Nat Commun 2018; 9:685. [PMID: 29449561 PMCID: PMC5814552 DOI: 10.1038/s41467-018-02914-9] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2017] [Accepted: 01/06/2018] [Indexed: 11/09/2022] Open
Abstract
Emergent physical properties often arise at interfaces of complex oxide heterostructures due to the interplay between various degrees of freedom, especially those with polar discontinuities. It is desirable to explore if these structures may generate pure and controllable spin currents, which are needed to attain unmatched performance and energy efficiency in the next-generation spintronic devices. Here we report the emergence of a spin-polarized two-dimensional electron gas (SP-2DEG) at the interface of two insulators, SrTiO3 and PbZr0.2Ti0.8O3. This SP-2DEG is strongly localized at the interfacial Ti atoms, due to the interplay between Coulomb interaction and band bending, and can be tuned by the ferroelectric polarization. Our findings open a door for engineering ferroelectric/insulator interfaces to create tunable ferroic orders for magnetoelectric device applications and provide opportunities for designing multiferroic materials in heterostructures. Two-dimensional electron gases that form in some complex oxide heterostructures may have useful functional behavior due to the interaction of the parent materials. Here the authors show that PZT/STO interfaces can host a spin-polarized electron gas, even though the bulk materials are nonmagnetic.
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Affiliation(s)
- Yi Zhang
- Department of Chemical Engineering and Materials Science, University of California, Irvine, CA, 92697, USA
| | - Lin Xie
- National Laboratory of Solid State Microstructures and College of Engineering and Applied Sciences, Nanjing University, Nanjing, Jiangsu, 210093, China
| | - Jeongwoo Kim
- Department of Physics and Astronomy, University of California, Irvine, CA, 92697, USA
| | - Alex Stern
- Department of Physics and Astronomy, University of California, Irvine, CA, 92697, USA
| | - Hui Wang
- Department of Physics and Astronomy, University of California, Irvine, CA, 92697, USA
| | - Kui Zhang
- Department of Chemical Engineering and Materials Science, University of California, Irvine, CA, 92697, USA
| | - Xingxu Yan
- Department of Chemical Engineering and Materials Science, University of California, Irvine, CA, 92697, USA
| | - Linze Li
- Department of Chemical Engineering and Materials Science, University of California, Irvine, CA, 92697, USA
| | - Henry Liu
- Department of Materials Science and Engineering, National Chiao Tung University, HsinChu, 30010, Taiwan
| | - Gejian Zhao
- Department of Physics, Arizona State University, Tempe, Arizona, 85287, USA
| | - Hang Chi
- Department of Physics, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Chaitanya Gadre
- Department of Physics and Astronomy, University of California, Irvine, CA, 92697, USA
| | - Qiyin Lin
- Irvine Materials Research Institute, University of California, Irvine, CA, 92697, USA
| | - Yichun Zhou
- School of Materials Science and Engineering, Xiangtan University, Xiangtan, 411105, Hunan, China
| | - Ctirad Uher
- Department of Physics, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Tingyong Chen
- Department of Physics, Arizona State University, Tempe, Arizona, 85287, USA
| | - Ying-Hao Chu
- Department of Materials Science and Engineering, National Chiao Tung University, HsinChu, 30010, Taiwan
| | - Jing Xia
- Department of Physics and Astronomy, University of California, Irvine, CA, 92697, USA
| | - Ruqian Wu
- Department of Physics and Astronomy, University of California, Irvine, CA, 92697, USA
| | - Xiaoqing Pan
- Department of Chemical Engineering and Materials Science, University of California, Irvine, CA, 92697, USA. .,Department of Physics and Astronomy, University of California, Irvine, CA, 92697, USA.
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23
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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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24
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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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25
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Zhou F, Liu Y, Lai Z, Liao M, Zhou Y, Huang Y, Zhu J. Quantum confined two-dimensional electron/hole gas switching by facet orientation of perovskite oxides. RSC Adv 2018; 8:20477-20482. [PMID: 35542364 PMCID: PMC9080832 DOI: 10.1039/c8ra03928c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2018] [Accepted: 05/29/2018] [Indexed: 11/21/2022] Open
Abstract
The Polar discontinuity at heterointerface and the bare surface reconstructs the electronic phase of perovskite oxides.
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Affiliation(s)
- Fei Zhou
- School of Materials Science and Engineering
- Harbin Institute of Technology
- Harbin
- China
- MIIT Key Laboratory of Critical Materials Technology for New Energy Conversion and Storage
| | - Yong Liu
- School of Materials Science and Engineering
- Harbin Institute of Technology
- Harbin
- China
- National Key Laboratory for Precision Hot Processing of Metals
| | - Zhonghong Lai
- Analysis and Testing Center
- Harbin Institute of Technology
- Harbin
- China
| | - Mingqing Liao
- School of Materials Science and Engineering
- Harbin Institute of Technology
- Harbin
- China
| | - Yi Zhou
- School of Materials Science and Engineering
- Harbin Institute of Technology
- Harbin
- China
| | - Yudong Huang
- MIIT Key Laboratory of Critical Materials Technology for New Energy Conversion and Storage
- School of Chemistry and Chemical Engineering, Harbin Institute of Technology
- Harbin
- China
| | - Jingchuan Zhu
- School of Materials Science and Engineering
- Harbin Institute of Technology
- Harbin
- China
- National Key Laboratory of Science and Technology on Advanced Composites in Special Environments
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26
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Plumb NC, Radović M. Angle-resolved photoemission spectroscopy studies of metallic surface and interface states of oxide insulators. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2017; 29:433005. [PMID: 28961143 DOI: 10.1088/1361-648x/aa833f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Over the last decade, conducting states embedded in insulating transition metal oxides (TMOs) have served as gateways to discovering and probing surprising phenomena that can emerge in complex oxides, while also opening opportunities for engineering advanced devices. These states are commonly realized at thin film interfaces, such as the well-known case of LaAlO3 (LAO) grown on SrTiO3 (STO). In recent years, the use of angle-resolved photoemission spectroscopy (ARPES) to investigate the k-space electronic structure of such materials led to the discovery that metallic states can also be formed on the bare surfaces of certain TMOs. In this topical review, we report on recent studies of low-dimensional metallic states confined at insulating oxide surfaces and interfaces as seen from the perspective of ARPES, which provides a direct view of the occupied band structure. While offering a fairly broad survey of progress in the field, we draw particular attention to STO, whose surface is so far the best-studied, and whose electronic structure is probably of the most immediate interest, given the ubiquitous use of STO substrates as the basis for conducting oxide interfaces. The ARPES studies provide crucial insights into the electronic band structure, orbital character, dimensionality/confinement, spin structure, and collective excitations in STO surfaces and related oxide surface/interface systems. The obtained knowledge increases our understanding of these complex materials and gives new perspectives on how to manipulate their properties.
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Affiliation(s)
- Nicholas C Plumb
- Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
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27
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Controlled manipulation of oxygen vacancies using nanoscale flexoelectricity. Nat Commun 2017; 8:615. [PMID: 28931810 PMCID: PMC5607007 DOI: 10.1038/s41467-017-00710-5] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2016] [Accepted: 07/18/2017] [Indexed: 11/09/2022] Open
Abstract
Oxygen vacancies, especially their distribution, are directly coupled to the electromagnetic properties of oxides and related emergent functionalities that have implications for device applications. Here using a homoepitaxial strontium titanate thin film, we demonstrate a controlled manipulation of the oxygen vacancy distribution using the mechanical force from a scanning probe microscope tip. By combining Kelvin probe force microscopy imaging and phase-field simulations, we show that oxygen vacancies can move under a stress-gradient-induced depolarisation field. When tailored, this nanoscale flexoelectric effect enables a controlled spatial modulation. In motion, the scanning probe tip thereby deterministically reconfigures the spatial distribution of vacancies. The ability to locally manipulate oxygen vacancies on-demand provides a tool for the exploration of mesoscale quantum phenomena and engineering multifunctional oxide devices.The properties of complex oxides such as strontium titanate are strongly affected by the presence and distribution of oxygen vacancies. Here, the authors demonstrate that a scanning probe microscope tip can be used to manipulate vacancies by the flexoelectric effect.
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28
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Kepenekian M, Even J. Rashba and Dresselhaus Couplings in Halide Perovskites: Accomplishments and Opportunities for Spintronics and Spin-Orbitronics. J Phys Chem Lett 2017; 8:3362-3370. [PMID: 28661150 DOI: 10.1021/acs.jpclett.7b01015] [Citation(s) in RCA: 74] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
In halide hybrid organic-inorganic perovskites (HOPs), spin-orbit coupling (SOC) presents a well-documented large influence on band structure. However, SOC may also present more exotic effects, such as Rashba and Dresselhaus couplings. In this Perspective, we start by recalling the main features of this effect and what makes HOP materials ideal candidates for the generation and tuning of spin-states. Then, we detail the main spectroscopy techniques able to characterize these effects and their application to HOPs. Finally, we discuss potential applications in spintronics and in spin-orbitronics in those nonmagnetic systems, which would complete the skill set of HOPs and perpetuate their ride on the crest of the wave of popularity started with optoelectronics and photovoltaics.
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Affiliation(s)
- Mikaël Kepenekian
- Institut des Sciences Chimiques de Rennes, UMR 6226, CNRS - Université de Rennes 1, 35700 Rennes, France
| | - Jacky Even
- Fonctions Optiques pour les Technologies de l'Information (FOTON), INSA de Rennes, CNRS, UMR 6082, 35708 Rennes, France
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29
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Klimovskikh II, Shikin AM, Otrokov MM, Ernst A, Rusinov IP, Tereshchenko OE, Golyashov VA, Sánchez-Barriga J, Varykhalov AY, Rader O, Kokh KA, Chulkov EV. Giant Magnetic Band Gap in the Rashba-Split Surface State of Vanadium-Doped BiTeI: A Combined Photoemission and Ab Initio Study. Sci Rep 2017; 7:3353. [PMID: 28611416 PMCID: PMC5469768 DOI: 10.1038/s41598-017-03507-0] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2017] [Accepted: 04/28/2017] [Indexed: 12/01/2022] Open
Abstract
One of the most promising platforms for spintronics and topological quantum computation is the two-dimensional electron gas (2DEG) with strong spin-orbit interaction and out-of-plane ferromagnetism. In proximity to an s-wave superconductor, such 2DEG may be driven into a topologically non-trivial superconducting phase, predicted to support zero-energy Majorana fermion modes. Using angle-resolved photoemission spectroscopy and ab initio calculations, we study the 2DEG at the surface of the vanadium-doped polar semiconductor with a giant Rashba-type splitting, BiTeI. We show that the vanadium-induced magnetization in the 2DEG breaks time-reversal symmetry, lifting Kramers degeneracy of the Rashba-split surface state at the Brillouin zone center via formation of a huge gap of about 90 meV. As a result, the constant energy contour inside the gap consists of only one circle with spin-momentum locking. These findings reveal a great potential of the magnetically-doped semiconductors with a giant Rashba-type splitting for realization of novel states of matter.
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Affiliation(s)
- I I Klimovskikh
- Saint Petersburg State University, 198504, Saint Petersburg, Russia.
| | - A M Shikin
- Saint Petersburg State University, 198504, Saint Petersburg, Russia
| | - M M Otrokov
- Saint Petersburg State University, 198504, Saint Petersburg, Russia
- Tomsk State University, 634050, Tomsk, Russia
- Donostia International Physics Center (DIPC), 20018 San Sebastián/Donostia, Basque Country, Spain
| | - A Ernst
- Max Planck Institute of Microstructure Physics, Weinberg 2, 06120, Halle, Germany
- Institut für Theoretische Physik, Johannes Kepler Universität, A 4040, Linz, Austria
| | - I P Rusinov
- Saint Petersburg State University, 198504, Saint Petersburg, Russia
- Tomsk State University, 634050, Tomsk, Russia
| | - O E Tereshchenko
- Saint Petersburg State University, 198504, Saint Petersburg, Russia
- A.V. Rzhanov Institute of Semiconductor Physics, 630090, Novosibirsk, Russia
- Novosibirsk State University, 630090, Novosibirsk, Russia
| | - V A Golyashov
- Saint Petersburg State University, 198504, Saint Petersburg, Russia
- A.V. Rzhanov Institute of Semiconductor Physics, 630090, Novosibirsk, Russia
| | - J Sánchez-Barriga
- Helmholtz-Zentrum Berlin für Materialien und Energie, Elektronenspeicherring BESSY II, Albert-Einstein-Strasse 15, 12489, Berlin, Germany
| | - A Yu Varykhalov
- Helmholtz-Zentrum Berlin für Materialien und Energie, Elektronenspeicherring BESSY II, Albert-Einstein-Strasse 15, 12489, Berlin, Germany
| | - O Rader
- Helmholtz-Zentrum Berlin für Materialien und Energie, Elektronenspeicherring BESSY II, Albert-Einstein-Strasse 15, 12489, Berlin, Germany
| | - K A Kokh
- Saint Petersburg State University, 198504, Saint Petersburg, Russia
- Novosibirsk State University, 630090, Novosibirsk, Russia
- V.S. Sobolev Institute of Geology and Mineralogy, 630090, Novosibirsk, Russia
| | - E V Chulkov
- Saint Petersburg State University, 198504, Saint Petersburg, Russia
- Tomsk State University, 634050, Tomsk, Russia
- Donostia International Physics Center (DIPC), 20018 San Sebastián/Donostia, Basque Country, Spain
- Departamento de Física de Materiales UPV/EHU, Centro de Física de Materiales CFM - MPC and Centro Mixto CSIC-UPV/EHU, 20080 San Sebastián/Donostia, Basque Country, Spain
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30
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Generalov A, Otrokov MM, Chikina A, Kliemt K, Kummer K, Höppner M, Güttler M, Seiro S, Fedorov A, Schulz S, Danzenbächer S, Chulkov EV, Geibel C, Laubschat C, Dudin P, Hoesch M, Kim T, Radovic M, Shi M, Plumb NC, Krellner C, Vyalikh DV. Spin Orientation of Two-Dimensional Electrons Driven by Temperature-Tunable Competition of Spin-Orbit and Exchange-Magnetic Interactions. NANO LETTERS 2017; 17:811-820. [PMID: 28032768 DOI: 10.1021/acs.nanolett.6b04036] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Finding ways to create and control the spin-dependent properties of two-dimensional electron states (2DESs) is a major challenge for the elaboration of novel spin-based devices. Spin-orbit and exchange-magnetic interactions (SOI and EMI) are two fundamental mechanisms that enable access to the tunability of spin-dependent properties of carriers. The silicon surface of HoRh2Si2 appears to be a unique model system, where concurrent SOI and EMI can be visualized and controlled by varying the temperature. The beauty and simplicity of this system lie in the 4f moments, which act as a multiple tuning instrument on the 2DESs, as the 4f projections parallel and perpendicular to the surface order at essentially different temperatures. Here we show that the SOI locks the spins of the 2DESs exclusively in the surface plane when the 4f moments are disordered: the Rashba-Bychkov effect. When the temperature is gradually lowered and the system experiences magnetic order, the rising EMI progressively competes with the SOI leading to a fundamental change in the spin-dependent properties of the 2DESs. The spins rotate and reorient toward the out-of-plane Ho 4f moments. Our findings show that the direction of the spins and the spin-splitting of the two-dimensional electrons at the surface can be manipulated in a controlled way by using only one parameter: the temperature.
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Affiliation(s)
| | - Mikhail M Otrokov
- Departamento de Fisica de Materiales and CFM-MPC UPV/EHU, Donostia International Physics Center (DIPC) , 20080 San Sebastian, Spain
- Tomsk State University, Lenina Av., 36, 634050 Tomsk, Russia
| | - Alla Chikina
- Institute of Solid State Physics, Dresden University of Technology , Zellescher Weg 16, D-01062 Dresden, Germany
| | - Kristin Kliemt
- Kristall- und Materiallabor, Physikalisches Institut, Goethe-Universität Frankfurt , Max-von-Laue Straße 1, D-60438 Frankfurt am Main, Germany
| | - Kurt Kummer
- European Synchrotron Radiation Facility, 71 Avenue des Martyrs, CS40220, F-38043 Grenoble Cedex 9, France
| | - Marc Höppner
- Max Planck Institute for Solid State Research, Heisenberg Straße 1, D-70569 Stuttgart, Germany
| | - Monika Güttler
- Institute of Solid State Physics, Dresden University of Technology , Zellescher Weg 16, D-01062 Dresden, Germany
| | - Silvia Seiro
- Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, D-01187 Dresden, Germany
| | | | - Susanne Schulz
- Institute of Solid State Physics, Dresden University of Technology , Zellescher Weg 16, D-01062 Dresden, Germany
| | - Steffen Danzenbächer
- Institute of Solid State Physics, Dresden University of Technology , Zellescher Weg 16, D-01062 Dresden, Germany
| | - Evgueni V Chulkov
- Departamento de Fisica de Materiales and CFM-MPC UPV/EHU, Donostia International Physics Center (DIPC) , 20080 San Sebastian, Spain
- Tomsk State University, Lenina Av., 36, 634050 Tomsk, Russia
- Saint Petersburg State University , 198504 Saint Petersburg, Russia
| | - Christoph Geibel
- Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, D-01187 Dresden, Germany
| | - Clemens Laubschat
- Institute of Solid State Physics, Dresden University of Technology , Zellescher Weg 16, D-01062 Dresden, Germany
| | | | | | - Timur Kim
- Diamond Light Source, Didcot OX11 0DE, U.K
| | | | | | | | - Cornelius Krellner
- Kristall- und Materiallabor, Physikalisches Institut, Goethe-Universität Frankfurt , Max-von-Laue Straße 1, D-60438 Frankfurt am Main, Germany
| | - Denis V Vyalikh
- Departamento de Fisica de Materiales and CFM-MPC UPV/EHU, Donostia International Physics Center (DIPC) , 20080 San Sebastian, Spain
- Institute of Solid State Physics, Dresden University of Technology , Zellescher Weg 16, D-01062 Dresden, Germany
- Saint Petersburg State University , 198504 Saint Petersburg, Russia
- IKERBASQUE, Basque Foundation for Science , 48011 Bilbao, Spain
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31
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Tian B, Nukala P, Hassine MB, Zhao X, Wang X, Shen H, Wang J, Sun S, Lin T, Sun J, Ge J, Huang R, Duan C, Reiss T, Varela M, Dkhil B, Meng X, Chu J. Interfacial memristors in Al–LaNiO3heterostructures. Phys Chem Chem Phys 2017. [DOI: 10.1039/c7cp02398g] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Self-assembled interfacial memristive systems in Al–LaNiO3heterostructures.
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32
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Coey JMD, Venkatesan M, Stamenov P. Surface magnetism of strontium titanate. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2016; 28:485001. [PMID: 27666311 DOI: 10.1088/0953-8984/28/48/485001] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
SrTiO3 plays a central role in oxide electronics. It is the substrate of choice for functional oxide heterostructures based on perovskite-structure thin-film stacks, and its surface or interface with a polar oxide such as LaAlO3 can become a 2D conductor because of electronic reconstruction or the presence of oxygen defects. Inconsistent reports of magnetic order in SrTiO3 abound in the literature. Here, we report a systematic experimental study aimed at establishing how and when SrTiO3 can develop a magnetic moment at room temperature. Polished (1 0 0), (1 1 0) or (1 1 1) crystal slices from four different suppliers are characterized before and after vacuum annealing at 750 °C, both in single-crystal and powdered form. Impurity content is analysed at the surface and in the bulk. Besides the underlying intrinsic diamagnetism of SrTiO3, magnetic signals are of three types-a Curie law susceptibility due to dilute magnetic impurities at the ppm level, a hysteretic temperature-dependent ferromagnetic impurity contribution, and a practically anhysteretic defect-related temperature-independent component that saturates in about 200 mT. The latter component is intrinsic. It is often the largest, reaching 10 μ B nm-2 of the surface area or more and dominating the magnetic response in low fields at room temperature. It is associated with defects near the surface, and can be destroyed by treatment with Tiron (C6H4Na2O8S2), an electron donor molecule that forms a strong complex with titanium at the surface. The origin of this unusual high-temperature ferromagnetic-like response is discussed.
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Affiliation(s)
- J M D Coey
- School of Physics, Trinity College, Dublin 2, Ireland
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33
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Krempaský J, Muff S, Bisti F, Fanciulli M, Volfová H, Weber AP, Pilet N, Warnicke P, Ebert H, Braun J, Bertran F, Volobuev VV, Minár J, Springholz G, Dil JH, Strocov VN. Entanglement and manipulation of the magnetic and spin-orbit order in multiferroic Rashba semiconductors. Nat Commun 2016; 7:13071. [PMID: 27767052 PMCID: PMC5078730 DOI: 10.1038/ncomms13071] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2016] [Accepted: 08/31/2016] [Indexed: 11/17/2022] Open
Abstract
Entanglement of the spin–orbit and magnetic order in multiferroic materials bears a strong potential for engineering novel electronic and spintronic devices. Here, we explore the electron and spin structure of ferroelectric α-GeTe thin films doped with ferromagnetic Mn impurities to achieve its multiferroic functionality. We use bulk-sensitive soft-X-ray angle-resolved photoemission spectroscopy (SX-ARPES) to follow hybridization of the GeTe valence band with the Mn dopants. We observe a gradual opening of the Zeeman gap in the bulk Rashba bands around the Dirac point with increase of the Mn concentration, indicative of the ferromagnetic order, at persistent Rashba splitting. Furthermore, subtle details regarding the spin–orbit and magnetic order entanglement are deduced from spin-resolved ARPES measurements. We identify antiparallel orientation of the ferroelectric and ferromagnetic polarization, and altering of the Rashba-type spin helicity by magnetic switching. Our experimental results are supported by first-principles calculations of the electron and spin structure. In α-GeTe, ferroelectric polarization acts to break inversion symmetry of the lattice and induce a strong Rashba-type spin splitting of the electronic band structure. Here, the authors study how this effect competes with Zeeman splitting due to ferromagnetic exchange coupling in Mn-doped GeTe.
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Affiliation(s)
- J Krempaský
- Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
| | - S Muff
- Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland.,Institute of Physics, École Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland
| | - F Bisti
- Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
| | - M Fanciulli
- Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland.,Institute of Physics, École Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland
| | - H Volfová
- Department of Chemistry, Ludwig Maximillian University, 81377 Munich, Germany
| | - A P Weber
- Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland.,Institute of Physics, École Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland
| | - N Pilet
- Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
| | - P Warnicke
- Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
| | - H Ebert
- Department of Chemistry, Ludwig Maximillian University, 81377 Munich, Germany
| | - J Braun
- Department of Chemistry, Ludwig Maximillian University, 81377 Munich, Germany
| | - F Bertran
- SOLEIL Synchrotron, L'Orme des Merisiers, F-91192 Gif-sur-Yvette, France
| | - V V Volobuev
- National Technical University, Kharkiv Polytechnic Institute, Frunze Str. 21, 61002 Kharkiv, Ukraine.,Institut für Halbleiter-und Festkörperphysik, Johannes Kepler Universität, A-4040 Linz, Austria
| | - J Minár
- Department of Chemistry, Ludwig Maximillian University, 81377 Munich, Germany.,New Technologies-Research Center University of West Bohemia, Plzeň, Czech Republic
| | - G Springholz
- Institut für Halbleiter-und Festkörperphysik, Johannes Kepler Universität, A-4040 Linz, Austria
| | - J H Dil
- Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland.,Institute of Physics, École Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland
| | - V N Strocov
- Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
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34
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Dudy L, Sing M, Scheiderer P, Denlinger JD, Schütz P, Gabel J, Buchwald M, Schlueter C, Lee TL, Claessen R. In Situ Control of Separate Electronic Phases on SrTiO3 Surfaces by Oxygen Dosing. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2016; 28:7443-7449. [PMID: 27332795 DOI: 10.1002/adma.201600046] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/05/2016] [Revised: 05/10/2016] [Indexed: 06/06/2023]
Abstract
Insulating SrTiO3 (STO) can host 2D electron systems (2DESs) on its surfaces, caused by oxygen defects. This study shows that the STO surface exhibits phase separation once the 2DES is formed and relates this inhomogeneity to recently reported magnetic order at STO surfaces and interfaces. The results open pathways to exploit oxygen defects for engineering the electronic and magnetic properties of oxides.
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Affiliation(s)
- Lenart Dudy
- Physikalisches Institut and Röntgen Center for Complex Material Systems (RCCM), Universität Würzburg, D-97074, Würzburg, Germany.
| | - Michael Sing
- Physikalisches Institut and Röntgen Center for Complex Material Systems (RCCM), Universität Würzburg, D-97074, Würzburg, Germany
| | - Philipp Scheiderer
- Physikalisches Institut and Röntgen Center for Complex Material Systems (RCCM), Universität Würzburg, D-97074, Würzburg, Germany
| | - Jonathan D Denlinger
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA, 94270, USA
| | - Philipp Schütz
- Physikalisches Institut and Röntgen Center for Complex Material Systems (RCCM), Universität Würzburg, D-97074, Würzburg, Germany
| | - Judith Gabel
- Physikalisches Institut and Röntgen Center for Complex Material Systems (RCCM), Universität Würzburg, D-97074, Würzburg, Germany
| | - Mathias Buchwald
- Physikalisches Institut and Röntgen Center for Complex Material Systems (RCCM), Universität Würzburg, D-97074, Würzburg, Germany
| | | | - Tien-Lin Lee
- Diamond Light Source Ltd, Didcot, Oxfordshire, OX11 0DE, UK
| | - Ralph Claessen
- Physikalisches Institut and Röntgen Center for Complex Material Systems (RCCM), Universität Würzburg, D-97074, Würzburg, Germany
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35
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Annese E, Kuzumaki T, Müller B, Yamamoto Y, Nakano H, Kato H, Araki A, Ohtaka M, Aoki T, Ishikawa H, Hayashida T, Osiecki JR, Miyamoto K, Takeichi Y, Harasawa A, Yaji K, Shirasawa T, Nittoh KI, Yang W, Miki K, Oda T, Yeom HW, Sakamoto K. Nonvortical Rashba Spin Structure on a Surface with C_{1h} Symmetry. PHYSICAL REVIEW LETTERS 2016; 117:016803. [PMID: 27419582 DOI: 10.1103/physrevlett.117.016803] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/12/2016] [Indexed: 06/06/2023]
Abstract
A totally anisotropic peculiar Rashba-Bychkov (RB) splitting of electronic bands was found on the Tl/Si(110)-(1×1) surface with C_{1h} symmetry by angle- and spin-resolved photoelectron spectroscopy and first-principles theoretical calculation. The constant energy contour of the upper branch of the RB split band has a warped elliptical shape centered at a k point located between Γ[over ¯] and the edge of the surface Brillouin zone, i.e., at a point without time-reversal symmetry. The spin-polarization vector of this state is in-plane and points almost the same direction along the whole elliptic contour. This novel nonvortical RB spin structure is confirmed as a general phenomenon originating from the C_{1h} symmetry of the surface.
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Affiliation(s)
- Emilia Annese
- Department of Nanomaterials Science, Chiba University, Chiba 263-8522, Japan
- Elettra Synchrotron S.C.p.A Trieste, SS 14, km 163.5, I-34149 Trieste, Italy
| | - Takuya Kuzumaki
- Department of Nanomaterials Science, Chiba University, Chiba 263-8522, Japan
| | - Beate Müller
- Department of Nanomaterials Science, Chiba University, Chiba 263-8522, Japan
| | - Yuta Yamamoto
- Department of Nanomaterials Science, Chiba University, Chiba 263-8522, Japan
| | - Hiroto Nakano
- Institute of Science and Engineering, Kanazawa University, Kanazawa 920-1192, Japan
| | - Haruki Kato
- Institute of Science and Engineering, Kanazawa University, Kanazawa 920-1192, Japan
| | - Atsushi Araki
- Institute of Science and Engineering, Kanazawa University, Kanazawa 920-1192, Japan
| | - Minoru Ohtaka
- Department of Nanomaterials Science, Chiba University, Chiba 263-8522, Japan
| | - Takashi Aoki
- Department of Nanomaterials Science, Chiba University, Chiba 263-8522, Japan
| | - Hirotaka Ishikawa
- Department of Nanomaterials Science, Chiba University, Chiba 263-8522, Japan
| | - Takashi Hayashida
- Department of Nanomaterials Science, Chiba University, Chiba 263-8522, Japan
| | | | - Koji Miyamoto
- Hiroshima Synchrotron Radiation Centre, Hiroshima University, Higashi-Hiroshima 739-0046, Japan
| | - Yasuo Takeichi
- Institute for Solid State Physics, The University of Tokyo, Chiba 277-8581, Japan
| | - Ayumi Harasawa
- Institute for Solid State Physics, The University of Tokyo, Chiba 277-8581, Japan
| | - Koichiro Yaji
- Institute for Solid State Physics, The University of Tokyo, Chiba 277-8581, Japan
| | - Tetsuroh Shirasawa
- Institute for Solid State Physics, The University of Tokyo, Chiba 277-8581, Japan
| | - Koh-Ichi Nittoh
- National Institute for Materials Science, Ibaraki 305-0044, Japan
| | - Wooil Yang
- Center for Artificial Low Dimensional Electronic Systems, Institute for Basic Science (IBS), Pohang 790-784, Korea
- Department of Physics, Pohang University of Science and Technology (POSTECH), Pohang 790-784, Korea
| | - Kazushi Miki
- National Institute for Materials Science, Ibaraki 305-0044, Japan
| | - Tatsuki Oda
- Institute of Science and Engineering, Kanazawa University, Kanazawa 920-1192, Japan
| | - Han Woong Yeom
- Center for Artificial Low Dimensional Electronic Systems, Institute for Basic Science (IBS), Pohang 790-784, Korea
- Department of Physics, Pohang University of Science and Technology (POSTECH), Pohang 790-784, Korea
| | - Kazuyuki Sakamoto
- Department of Nanomaterials Science, Chiba University, Chiba 263-8522, Japan
- Molecular Chirality Research Center, Chiba University, Chiba 263-8522, Japan
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36
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Taniuchi T, Motoyui Y, Morozumi K, Rödel TC, Fortuna F, Santander-Syro AF, Shin S. Imaging of room-temperature ferromagnetic nano-domains at the surface of a non-magnetic oxide. Nat Commun 2016; 7:11781. [PMID: 27283225 PMCID: PMC4906390 DOI: 10.1038/ncomms11781] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2015] [Accepted: 04/28/2016] [Indexed: 12/03/2022] Open
Abstract
Two-dimensional electron gases at oxide surfaces or interfaces show exotic ordered states of matter, like superconductivity, magnetism or spin-polarized states, and are a promising platform for alternative oxide-based electronics. Here we directly image a dense population of randomly distributed ferromagnetic domains of ∼40 nm typical sizes at room temperature at the oxygen-deficient surface of SrTiO3, a non-magnetic transparent insulator in the bulk. We use laser-based photoemission electron microscopy, an experimental technique that gives selective spin detection of the surface carriers, even in bulk insulators, with a high spatial resolution of 2.6 nm. We furthermore find that the Curie temperature in this system is as high as 900 K. These findings open perspectives for applications in nano-domain magnetism and spintronics using oxide-based devices, for instance through the nano-engineering of oxygen vacancies at surfaces or interfaces of transition-metal oxides. The surfaces of transition metal oxides exhibit a wide range of functional behaviours, from magnetism to superconductivity. Here, the authors use high-resolution microscopy to image the temperature dependent development of nanoscale ferromagnetic domains on an oxygen-deficient SrTiO3 surface.
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Affiliation(s)
- T Taniuchi
- Institute for Solid State Physics, University of Tokyo, Chiba 277-8581, Japan.,CREST, Japan Science and Technology Agency, Tokyo 102-0075, Japan
| | - Y Motoyui
- Institute for Solid State Physics, University of Tokyo, Chiba 277-8581, Japan
| | - K Morozumi
- Institute for Solid State Physics, University of Tokyo, Chiba 277-8581, Japan
| | - T C Rödel
- CSNSM, CNRS/IN2P3 and Université Paris-Sud, Bâtiments 104 et 108, Orsay 91405, France.,Synchrotron SOLEIL, L'Orme des Merisiers, Saint-Aubin-BP48, Gif-sur-Yvette 91192, France
| | - F Fortuna
- CSNSM, CNRS/IN2P3 and Université Paris-Sud, Bâtiments 104 et 108, Orsay 91405, France
| | - A F Santander-Syro
- CSNSM, CNRS/IN2P3 and Université Paris-Sud, Bâtiments 104 et 108, Orsay 91405, France
| | - S Shin
- Institute for Solid State Physics, University of Tokyo, Chiba 277-8581, Japan.,CREST, Japan Science and Technology Agency, Tokyo 102-0075, Japan
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37
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Kumar N, Kitoh A, Inoue IH. Anomalous enhancement of the sheet carrier density beyond the classic limit on a SrTiO3 surface. Sci Rep 2016; 6:25789. [PMID: 27174141 PMCID: PMC4865841 DOI: 10.1038/srep25789] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2016] [Accepted: 04/22/2016] [Indexed: 11/28/2022] Open
Abstract
Electrostatic carrier accumulation on an insulating (100) surface of SrTiO3 by fabricating a field effect transistor with Parylene-C (6 nm)/HfO2 (20 nm) bilayer gate insulator has revealed a mystifying phenomenon: sheet carrier density is about 10 times as large as ( is the sheet capacitance of the gate insulator, VG is the gate voltage, and e is the elementary charge). The channel is so clean to exhibit small subthreshod swing of 170 mV/decade and large mobility of 11 cm2/Vs for of 1 × 1014 cm−2 at room temperature. Since does not depend on either VG nor time duration, beyond is solely ascribed to negative charge compressibility of the carriers, which was in general considered as due to exchange interactions among electrons in the small limit. However, the observed is too large to be naively understood by the framework. Alternative ideas are proposed in this work.
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Affiliation(s)
- Neeraj Kumar
- National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba 305-8565, Japan
| | - Ai Kitoh
- National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba 305-8565, Japan
| | - Isao H Inoue
- National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba 305-8565, Japan
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38
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Rashba coupling amplification by a staggered crystal field. Nat Commun 2016; 7:11258. [PMID: 27089869 PMCID: PMC4838854 DOI: 10.1038/ncomms11258] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2016] [Accepted: 03/07/2016] [Indexed: 11/21/2022] Open
Abstract
There has been increasing interest in materials where relativistic effects induce non-trivial electronic states with promise for spintronics applications. One example is the splitting of bands with opposite spin chirality produced by the Rashba spin-orbit coupling in asymmetric potentials. Sizable splittings have been hitherto obtained using either heavy elements, where this coupling is intrinsically strong, or large surface electric fields. Here by means of angular resolved photoemission spectroscopy and first-principles calculations, we give evidence of a large Rashba coupling of 0.25 eV Å, leading to a remarkable band splitting up to 0.15 eV with hidden spin-chiral polarization in centrosymmetric BaNiS2. This is explained by a huge staggered crystal field of 1.4 V Å−1, produced by a gliding plane symmetry, that breaks inversion symmetry at the Ni site. This unexpected result in the absence of heavy elements demonstrates an effective mechanism of Rashba coupling amplification that may foster spin-orbit band engineering. Future spintronic devices may exploit spin-orbit interactions, which often emerge from broken symmetries and strongly influence electronic behaviour. Here, the authors evidence the amplification of Rashba coupling by a crystal field that breaks the local inversion symmetry at the Ni site in BaNiS2.
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39
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Altmeyer M, Jeschke HO, Hijano-Cubelos O, Martins C, Lechermann F, Koepernik K, Santander-Syro AF, Rozenberg MJ, Valentí R, Gabay M. Magnetism, Spin Texture, and In-Gap States: Atomic Specialization at the Surface of Oxygen-Deficient SrTiO_{3}. PHYSICAL REVIEW LETTERS 2016; 116:157203. [PMID: 27127984 DOI: 10.1103/physrevlett.116.157203] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/01/2015] [Indexed: 06/05/2023]
Abstract
Motivated by recent spin- and angular-resolved photoemission (SARPES) measurements of the two-dimensional electronic states confined near the (001) surface of oxygen-deficient SrTiO_{3}, we explore their spin structure by means of ab initio density functional theory (DFT) calculations of slabs. Relativistic nonmagnetic DFT calculations display Rashba-like spin winding with a splitting of a few meV and when surface magnetism on the Ti ions is included, bands become spin-split with an energy difference ∼100 meV at the Γ point, consistent with SARPES findings. While magnetism tends to suppress the effects of the relativistic Rashba interaction, signatures of it are still clearly visible in terms of complex spin textures. Furthermore, we observe an atomic specialization phenomenon, namely, two types of electronic contributions: one is from Ti atoms neighboring the oxygen vacancies that acquire rather large magnetic moments and mostly create in-gap states; another comes from the partly polarized t_{2g} itinerant electrons of Ti atoms lying further away from the oxygen vacancy, which form the two-dimensional electron system and are responsible for the Rashba spin winding and the spin splitting at the Fermi surface.
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Affiliation(s)
- Michaela Altmeyer
- Institut für Theoretische Physik, Goethe-Universtät Frankfurt, 60438 Frankfurt am Main, Germany
| | - Harald O Jeschke
- Institut für Theoretische Physik, Goethe-Universtät Frankfurt, 60438 Frankfurt am Main, Germany
| | - Oliver Hijano-Cubelos
- Laboratoire de Physique des Solides, Bat 510, Université Paris-Sud, 91405 Orsay, France
| | - Cyril Martins
- Laboratoire de Physique des Solides, Bat 510, Université Paris-Sud, 91405 Orsay, France
| | - Frank Lechermann
- I. Institut für Theoretische Physik, Universität Hamburg, 20355 Hamburg, Germany
- Institut für Keramische Hochleistungswerkstoffe, TU Hamburg-Harburg, D-21073 Hamburg, Germany
| | | | - Andrés F Santander-Syro
- CSNSM, Univ. Paris-Sud, CNRS/IN2P3, Université Paris-Saclay, Bât 104 et 108, 91405 Orsay, France
| | - Marcelo J Rozenberg
- Laboratoire de Physique des Solides, Bat 510, Université Paris-Sud, 91405 Orsay, France
| | - Roser Valentí
- Institut für Theoretische Physik, Goethe-Universtät Frankfurt, 60438 Frankfurt am Main, Germany
| | - Marc Gabay
- Laboratoire de Physique des Solides, Bat 510, Université Paris-Sud, 91405 Orsay, France
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40
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Papagno M, Eremeev SV, Fujii J, Aliev ZS, Babanly MB, Mahatha SK, Vobornik I, Mamedov NT, Pacilé D, Chulkov EV. Multiple Coexisting Dirac Surface States in Three-Dimensional Topological Insulator PbBi₆Te₁₀. ACS NANO 2016; 10:3518-3524. [PMID: 26895427 DOI: 10.1021/acsnano.5b07750] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
By means of angle-resolved photoemission spectroscopy (ARPES) measurements, we unveil the electronic band structure of three-dimensional PbBi6Te10 topological insulator. ARPES investigations evidence multiple coexisting Dirac surface states at the zone-center of the reciprocal space, displaying distinct electronic band dispersion, different constant energy contours, and Dirac point energies. We also provide evidence of Rashba-like split states close to the Fermi level, and deeper M- and V-shaped bands coexisting with the topological surface states. The experimental findings are in agreement with scanning tunneling microscopy measurements revealing different surface terminations according to the crystal structure of PbBi6Te10. Our experimental results are supported by density functional theory calculations predicting multiple topological surface states according to different surface cleavage planes.
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Affiliation(s)
- Marco Papagno
- Dipartimento di Fisica, Università della Calabria , 87036 Arcavacata di Rende, Calabria, Italy
| | - Sergey V Eremeev
- Institute of Strength Physics and Materials Science , 634021 Tomsk, Russia
- Tomsk State University , 634050 Tomsk, Russia
- Saint Petersburg State University , Saint Petersburg 198504, Russia
| | - Jun Fujii
- CNR-IOM, TASC Laboratory, AREA Science Park Basovizza, 34149 Trieste, Italy
| | - Ziya S Aliev
- Institute Catalysis and Inorganic Chemistry, Azerbaijan National Academy of Science , AZ1143 Baku, Azerbaijan
- Institute of Physics, Azerbaijan National Academy of Science , AZ1143 Baku, Azerbaijan
| | - Mahammad B Babanly
- Institute Catalysis and Inorganic Chemistry, Azerbaijan National Academy of Science , AZ1143 Baku, Azerbaijan
| | - Sanjoy Kr Mahatha
- Istituto di Struttura della Materia, Consiglio Nazionale delle Ricerche, 34149 Trieste, Italy
| | - Ivana Vobornik
- CNR-IOM, TASC Laboratory, AREA Science Park Basovizza, 34149 Trieste, Italy
| | - Nazim T Mamedov
- Institute of Physics, Azerbaijan National Academy of Science , AZ1143 Baku, Azerbaijan
| | - Daniela Pacilé
- Dipartimento di Fisica, Università della Calabria , 87036 Arcavacata di Rende, Calabria, Italy
| | - Evgueni V Chulkov
- Tomsk State University , 634050 Tomsk, Russia
- Saint Petersburg State University , Saint Petersburg 198504, Russia
- Donostia International Physics Center (DIPC), 20018 San Sebastián/Donostia, Basque Country, Spain
- Departamento de Física de Materiales UPV/EHU, Centro de Física de Materiales CFM-MPC and Centro Mixto CSIC-UPV/EHU, 20080 San Sebastián/Donostia, Basque Country, Spain
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41
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Truccato M, Agostino A, Borfecchia E, Mino L, Cara E, Pagliero A, Adhlakha N, Pascale L, Operti L, Enrico E, De Leo N, Fretto M, Martinez-Criado G, Lamberti C. Direct-Write X-ray Nanopatterning: A Proof of Concept Josephson Device on Bi2Sr2CaCu2O8+δ Superconducting Oxide. NANO LETTERS 2016; 16:1669-1674. [PMID: 26814601 DOI: 10.1021/acs.nanolett.5b04568] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
We describe the first use of a novel photoresist-free X-ray nanopatterning technique to fabricate an electronic device. We have produced a proof-of-concept device consisting of a few Josephson junctions by irradiating microcrystals of the Bi2Sr2CaCu2O8+δ (Bi-2212) superconducting oxide with a 17.6 keV synchrotron nanobeam. Fully functional devices have been obtained by locally turning the material into a nonsuperconducting state by means of hard X-ray exposure. Nano-XRD patterns reveal that the crystallinity is substantially preserved in the irradiated areas that there is no evidence of macroscopic crystal disruption. Indications are that O ions have been removed from the crystals, which could make this technique interesting also for other oxide materials. Direct-write X-ray nanopatterning represents a promising fabrication method exploiting material/material rather than vacuum/material interfaces, with the potential for nanometric resolution, improved mechanical stability, enhanced depth of patterning, and absence of chemical contamination with respect to traditional lithographic techniques.
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Affiliation(s)
- Marco Truccato
- Department of Physics, Interdepartmental Centre NIS, University of Torino , via Giuria 1, I-10125 Torino, Italy
| | - Angelo Agostino
- Department of Chemistry, Interdepartmental Centre NIS and INSTM Centro di Riferimento, University of Torino , via Giuria 7, I-10125 Torino, Italy
| | - Elisa Borfecchia
- Department of Chemistry, Interdepartmental Centre NIS and INSTM Centro di Riferimento, University of Torino , via Giuria 7, I-10125 Torino, Italy
| | - Lorenzo Mino
- INRIM, National Institute for Metrological Research , Strada delle Cacce 91, I-10135 Torino, Italy
| | - Eleonora Cara
- Department of Physics, Interdepartmental Centre NIS, University of Torino , via Giuria 1, I-10125 Torino, Italy
| | - Alessandro Pagliero
- Department of Physics, Interdepartmental Centre NIS, University of Torino , via Giuria 1, I-10125 Torino, Italy
| | - Nidhi Adhlakha
- Department of Physics, Interdepartmental Centre NIS, University of Torino , via Giuria 1, I-10125 Torino, Italy
| | - Lise Pascale
- Department of Chemistry, Interdepartmental Centre NIS and INSTM Centro di Riferimento, University of Torino , via Giuria 7, I-10125 Torino, Italy
| | - Lorenza Operti
- Department of Chemistry, Interdepartmental Centre NIS and INSTM Centro di Riferimento, University of Torino , via Giuria 7, I-10125 Torino, Italy
| | - Emanuele Enrico
- INRIM, National Institute for Metrological Research , Strada delle Cacce 91, I-10135 Torino, Italy
| | - Natascia De Leo
- INRIM, National Institute for Metrological Research , Strada delle Cacce 91, I-10135 Torino, Italy
| | - Matteo Fretto
- INRIM, National Institute for Metrological Research , Strada delle Cacce 91, I-10135 Torino, Italy
| | - Gema Martinez-Criado
- Experiments Division, European Synchrotron Radiation Facility , 71 Avenue des Martyrs, 38000 Grenoble, France
| | - Carlo Lamberti
- Department of Chemistry, Interdepartmental Centre NIS and INSTM Centro di Riferimento, University of Torino , via Giuria 7, I-10125 Torino, Italy
- Southern Federal University , Zorge Street 5, 344090 Rostov-on-Don, Russia
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42
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Rödel TC, Fortuna F, Sengupta S, Frantzeskakis E, Le Fèvre P, Bertran F, Mercey B, Matzen S, Agnus G, Maroutian T, Lecoeur P, Santander-Syro AF. Universal Fabrication of 2D Electron Systems in Functional Oxides. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2016; 28:1976-1980. [PMID: 26753522 DOI: 10.1002/adma.201505021] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/12/2015] [Revised: 11/19/2015] [Indexed: 06/05/2023]
Abstract
2D electron systems (2DESs) in functional oxides are promising for applications, but their fabrication and use, essentially limited to SrTiO3 -based heterostructures, are hampered by the need for growing complex oxide overlayers thicker than 2 nm using evolved techniques. It is demonstrated that thermal deposition of a monolayer of an elementary reducing agent suffices to create 2DESs in numerous oxides.
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Affiliation(s)
- Tobias Chris Rödel
- CSNSM, Univ. Paris-Sud, CNRS/IN2P3, Université Paris-Saclay, 91405, Orsay, France
- Synchrotron SOLEIL, L'Orme des Merisiers, Saint-Aubin-BP48, 91192, Gif-sur-Yvette, France
| | - Franck Fortuna
- CSNSM, Univ. Paris-Sud, CNRS/IN2P3, Université Paris-Saclay, 91405, Orsay, France
| | - Shamashis Sengupta
- Laboratoire de Physique des Solides, Univ. Paris-Sud, CNRS, Université Paris-Saclay, 91405, Orsay, France
| | | | - Patrick Le Fèvre
- Synchrotron SOLEIL, L'Orme des Merisiers, Saint-Aubin-BP48, 91192, Gif-sur-Yvette, France
| | - François Bertran
- Synchrotron SOLEIL, L'Orme des Merisiers, Saint-Aubin-BP48, 91192, Gif-sur-Yvette, France
| | - Bernard Mercey
- CRISMAT, ENSICAEN-CNRS UMR6508, 6 bd. Maréchal Juin, 14050, Caen, France
| | - Sylvia Matzen
- Institut d'Electronique Fondamentale, Univ. Paris-Sud, CNRS, Université Paris-Saclay, 91405, Orsay, France
| | - Guillaume Agnus
- Institut d'Electronique Fondamentale, Univ. Paris-Sud, CNRS, Université Paris-Saclay, 91405, Orsay, France
| | - Thomas Maroutian
- Institut d'Electronique Fondamentale, Univ. Paris-Sud, CNRS, Université Paris-Saclay, 91405, Orsay, France
| | - Philippe Lecoeur
- Institut d'Electronique Fondamentale, Univ. Paris-Sud, CNRS, Université Paris-Saclay, 91405, Orsay, France
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43
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Kepenekian M, Robles R, Katan C, Sapori D, Pedesseau L, Even J. Rashba and Dresselhaus Effects in Hybrid Organic-Inorganic Perovskites: From Basics to Devices. ACS NANO 2015; 9:11557-11567. [PMID: 26348023 DOI: 10.1021/acsnano.5b04409] [Citation(s) in RCA: 144] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
We use symmetry analysis, density functional theory calculations, and k·p modeling to scrutinize Rashba and Dresselhaus effects in hybrid organic-inorganic halide perovskites. These perovskites are at the center of a recent revolution in the field of photovoltaics but have also demonstrated potential for optoelectronic applications such as transistors and light emitters. Due to a large spin-orbit coupling of the most frequently used metals, they are also predicted to offer a promising avenue for spin-based applications. With an in-depth inspection of the electronic structures and bulk lattice symmetries of a variety of systems, we analyze the origin of the spin splitting in two- and three-dimensional hybrid perovskites. It is shown that low-dimensional nanostructures made of CH3NH3PbX3 (X = I, Br) lead to spin splittings that can be controlled by an applied electric field. These findings further open the door for a perovskite-based spintronics.
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Affiliation(s)
- Mikaël Kepenekian
- Institut des Sciences Chimiques de Rennes, UMR 6226, CNRS - Université de Rennes 1 35700 Rennes, France
| | - Roberto Robles
- ICN2 - Institut Catala de Nanociencia i Nanotecnologia , Campus UAB, 08193 Bellaterra, Barcelona, Spain
| | - Claudine Katan
- Institut des Sciences Chimiques de Rennes, UMR 6226, CNRS - Université de Rennes 1 35700 Rennes, France
| | - Daniel Sapori
- Université Européenne de Bretagne , INSA, FOTON UMR 6082, 35708 Rennes, France
| | - Laurent Pedesseau
- Université Européenne de Bretagne , INSA, FOTON UMR 6082, 35708 Rennes, France
| | - Jacky Even
- Université Européenne de Bretagne , INSA, FOTON UMR 6082, 35708 Rennes, France
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44
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Krasovskii EE. Spin-orbit coupling at surfaces and 2D materials. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2015; 27:493001. [PMID: 26580290 DOI: 10.1088/0953-8984/27/49/493001] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Spin-orbit interaction gives rise to a splitting of surface states via the Rashba effect, and in topological insulators it leads to the existence of topological surface states. The resulting k(//) momentum separation between states with the opposite spin underlies a wide range of new phenomena at surfaces and interfaces, such as spin transfer, spin accumulation, spin-to-charge current conversion, which are interesting for fundamental science and may become the basis for a breakthrough in the spintronic technology. The present review summarizes recent theoretical and experimental efforts to reveal the microscopic structure and mechanisms of spin-orbit driven phenomena with the focus on angle and spin-resolved photoemission and scanning tunneling microscopy.
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Affiliation(s)
- E E Krasovskii
- Departamento de Física de Materiales, Universidad del Pais Vasco UPV/EHU, 20080 San Sebastián/Donostia, Spain. Donostia International Physics Center (DIPC), 20018 San Sebastián/Donostia, Spain. IKERBASQUE, Basque Foundation for Science, 48013 Bilbao, Spain
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45
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Sarantopoulos A, Ferreiro-Vila E, Pardo V, Magén C, Aguirre MH, Rivadulla F. Electronic Degeneracy and Intrinsic Magnetic Properties of EpitaxialNb: SrTiO3 Thin Films Controlled by Defects. PHYSICAL REVIEW LETTERS 2015; 115:166801. [PMID: 26550891 DOI: 10.1103/physrevlett.115.166801] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/08/2015] [Indexed: 06/05/2023]
Abstract
We report thermoelectric power experiments in e-doped thin films of SrTiO3 (STO) which demonstrate that the electronic band degeneracy can be lifted through defect management during growth. We show that even small amounts of cationic vacancies, combined with epitaxial stress, produce a homogeneous tetragonal distortion of the films, resulting in a Kondo-like resistance upturn at low temperature, large anisotropic magnetoresistance, and nonlinear Hall effect. Ab initio calculations confirm a different occupation of each band depending on the degree of tetragonal distortion. The phenomenology reported in this Letter for tetragonally distorted e-doped STO thin films, is similar to that observed in LaAlO3/STO interfaces and magnetic STO quantum wells.
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Affiliation(s)
- A Sarantopoulos
- Centro de Investigación en Química Biológica y Materiales Moleculares (CIQUS), Universidad de Santiago de Compostela, 15782-Santiago de Compostela, Spain
| | - E Ferreiro-Vila
- Centro de Investigación en Química Biológica y Materiales Moleculares (CIQUS), Universidad de Santiago de Compostela, 15782-Santiago de Compostela, Spain
| | - V Pardo
- Departamento de Física Aplicada, Universidade de Santiago de Compostela, Santiago de Compostela, Spain
- Instituto de Investigacións Tecnolóxicas, Universidade de Santiago de Compostela, Santiago de Compostela, Spain
| | - C Magén
- Laboratorio de Microscopás Avanzadas, Instituto de Nanociencia de Aragón, Universidad de Zaragoza, 50018 Zaragoza, Spain
- Departamento de Física de la Materia Condensada, Universidad de Zaragoza, 50009 Zaragoza, Spain
- Fundación ARAID, 50018 Zaragoza, Spain
| | - M H Aguirre
- Laboratorio de Microscopás Avanzadas, Instituto de Nanociencia de Aragón, Universidad de Zaragoza, 50018 Zaragoza, Spain
- Departamento de Física de la Materia Condensada, Universidad de Zaragoza, 50009 Zaragoza, Spain
| | - F Rivadulla
- Centro de Investigación en Química Biológica y Materiales Moleculares (CIQUS), Universidad de Santiago de Compostela, 15782-Santiago de Compostela, Spain
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46
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Observation of correlated spin-orbit order in a strongly anisotropic quantum wire system. Nat Commun 2015; 6:8118. [PMID: 26356187 DOI: 10.1038/ncomms9118] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2014] [Accepted: 07/21/2015] [Indexed: 11/08/2022] Open
Abstract
Quantum wires with spin-orbit coupling provide a unique opportunity to simultaneously control the coupling strength and the screened Coulomb interactions where new exotic phases of matter can be explored. Here we report on the observation of an exotic spin-orbit density wave in Pb-atomic wires on Si(557) surfaces by mapping out the evolution of the modulated spin-texture at various conditions with spin- and angle-resolved photoelectron spectroscopy. The results are independently quantified by surface transport measurements. The spin polarization, coherence length, spin dephasing rate and the associated quasiparticle gap decrease simultaneously as the screened Coulomb interaction decreases with increasing excess coverage, providing a new mechanism for generating and manipulating a spin-orbit entanglement effect via electronic interaction. Despite clear evidence of spontaneous spin-rotation symmetry breaking and modulation of spin-momentum structure as a function of excess coverage, the average spin polarization over the Brillouin zone vanishes, indicating that time-reversal symmetry is intact as theoretically predicted.
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47
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Gor'kov LP. Antiferromagnetism of two-dimensional electronic gas on light-irradiated SrTiO3 and at LaAlO3/SrTiO3 interfaces. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2015; 27:252001. [PMID: 26020368 DOI: 10.1088/0953-8984/27/25/252001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
To gain an insight into the origin of tunable two-dimensional (2D) electronic liquid at the interfaces of transition-metal oxides, we address properties of a conducting layer on the light-irradiated surfaces of SrTiO3; the energy spectrum of the latter is known and consists of the titanium dxz/dyz and dxy bands. Recently, Santander-Syro et al (2014 Nature Mater. 13 1085) revealed that the dxy bands actually comprise two chiral branches with the Kramers degeneracy at the zone center lifted in the absence of a magnetic moment. We suggest that interacting electrons on the irradiated SrTiO3 go over into a magnetic phase as the result of one of the instabilities of the 2D Fermi liquid with exchange interactions, and point out the concrete antiferromagnetic order parameter. Large energy scales of the order of Fermi energy ∼0.1 eV inherent in this mechanism warrant stability of the magnetic ground state against ever-present effects of disorder. Arguments are given that electrons at the irradiated SrTiO3 surface and at the LaAlO3/SrTiO3 interfaces undergo a kind of first-order transformation into one and the same phase of the 2D electronic Fermi liquid with reduced magnetic symmetry.
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Affiliation(s)
- L P Gor'kov
- NHMFL, Florida State University, 1800 East Paul Dirac Drive, Tallahassee, FL 32310, USA. L.D. Landau Institute for Theoretical Physics of the RAS, Chernogolovka 142432, Russia
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48
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Herranz G, Singh G, Bergeal N, Jouan A, Lesueur J, Gázquez J, Varela M, Scigaj M, Dix N, Sánchez F, Fontcuberta J. Engineering two-dimensional superconductivity and Rashba spin-orbit coupling in LaAlO₃/SrTiO₃ quantum wells by selective orbital occupancy. Nat Commun 2015; 6:6028. [PMID: 25583368 PMCID: PMC4308716 DOI: 10.1038/ncomms7028] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2014] [Accepted: 12/03/2014] [Indexed: 11/09/2022] Open
Abstract
The discovery of two-dimensional electron gases (2DEGs) at oxide interfaces-involving electrons in narrow d-bands-has broken new ground, enabling the access to correlated states that are unreachable in conventional semiconductors based on s- and p- electrons. There is a growing consensus that emerging properties at these novel quantum wells-such as 2D superconductivity and magnetism-are intimately connected to specific orbital symmetries in the 2DEG sub-band structure. Here we show that crystal orientation allows selective orbital occupancy, disclosing unprecedented ways to tailor the 2DEG properties. By carrying out electrostatic gating experiments in LaAlO3/SrTiO3 wells of different crystal orientations, we show that the spatial extension and anisotropy of the 2D superconductivity and the Rashba spin-orbit field can be largely modulated by controlling the 2DEG sub-band filling. Such an orientational tuning expands the possibilities for electronic engineering of 2DEGs at LaAlO3/SrTiO3 interfaces.
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Affiliation(s)
- Gervasi Herranz
- Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Campus de la UAB, 08193 Bellaterra, Catalonia, Spain
| | - Gyanendra Singh
- LPEM-UMR8213/CNRS-ESPCI ParisTech-UPMC, PSL University, 10 rue Vauquelin, 75005 Paris, France
| | - Nicolas Bergeal
- LPEM-UMR8213/CNRS-ESPCI ParisTech-UPMC, PSL University, 10 rue Vauquelin, 75005 Paris, France
| | - Alexis Jouan
- LPEM-UMR8213/CNRS-ESPCI ParisTech-UPMC, PSL University, 10 rue Vauquelin, 75005 Paris, France
| | - Jérôme Lesueur
- LPEM-UMR8213/CNRS-ESPCI ParisTech-UPMC, PSL University, 10 rue Vauquelin, 75005 Paris, France
| | - Jaume Gázquez
- Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Campus de la UAB, 08193 Bellaterra, Catalonia, Spain
| | - María Varela
- 1] Materials Science &Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA [2] GFMC, Department de Fisica Aplicada III &Instituto Pluridisciplinar, Universidad Complutense de Madrid, 28040 Madrid, Spain
| | - Mateusz Scigaj
- 1] Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Campus de la UAB, 08193 Bellaterra, Catalonia, Spain [2] Departament de Física, Universitat Autònoma de Barcelona, E-08193 Bellaterra, Barcelona, Catalonia, Spain
| | - Nico Dix
- Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Campus de la UAB, 08193 Bellaterra, Catalonia, Spain
| | - Florencio Sánchez
- Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Campus de la UAB, 08193 Bellaterra, Catalonia, Spain
| | - Josep Fontcuberta
- Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Campus de la UAB, 08193 Bellaterra, Catalonia, Spain
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