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Xu H, Li H, Gauquelin N, Chen X, Wu WF, Zhao Y, Si L, Tian D, Li L, Gan Y, Qi S, Li M, Hu F, Sun J, Jannis D, Yu P, Chen G, Zhong Z, Radovic M, Verbeeck J, Chen Y, Shen B. Giant Tunability of Rashba Splitting at Cation-Exchanged Polar Oxide Interfaces by Selective Orbital Hybridization. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2024; 36:e2313297. [PMID: 38475975 DOI: 10.1002/adma.202313297] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/07/2023] [Revised: 03/07/2024] [Indexed: 03/14/2024]
Abstract
The 2D electron gas (2DEG) at oxide interfaces exhibits extraordinary properties, such as 2D superconductivity and ferromagnetism, coupled to strongly correlated electrons in narrow d-bands. In particular, 2DEGs in KTaO3 (KTO) with 5d t2g orbitals exhibit larger atomic spin-orbit coupling and crystal-facet-dependent superconductivity absent for 3d 2DEGs in SrTiO3 (STO). Herein, by tracing the interfacial chemistry, weak anti-localization magneto-transport behavior, and electronic structures of (001), (110), and (111) KTO 2DEGs, unambiguously cation exchange across KTO interfaces is discovered. Therefore, the origin of the 2DEGs at KTO-based interfaces is dramatically different from the electronic reconstruction observed at STO interfaces. More importantly, as the interface polarization grows with the higher order planes in the KTO case, the Rashba spin splitting becomes maximal for the superconducting (111) interfaces approximately twice that of the (001) interface. The larger Rashba spin splitting couples strongly to the asymmetric chiral texture of the orbital angular moment, and results mainly from the enhanced inter-orbital hopping of the t2g bands and more localized wave functions. This finding has profound implications for the search for topological superconductors, as well as the realization of efficient spin-charge interconversion for low-power spin-orbitronics based on (110) and (111) KTO interfaces.
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Affiliation(s)
- Hao Xu
- Beijing National Laboratory of Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Hang Li
- Photon Science Division, Paul Scherrer Institute, Villigen, 5232, Switzerland
| | - Nicolas Gauquelin
- Electron Microscopy for Materials Science (EMAT), University of Antwerp, 4Groenenborgerlaan 171, Antwerp, 2020, Belgium
| | - Xuejiao Chen
- CAS Key Laboratory of Magnetic Materials and Devices and Zhejiang Province Key Laboratory of Magnetic Materials and Application Technology, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo, 315201, China
| | - Wen-Feng Wu
- Key Laboratory of Materials Physics, Institute of Solid State Physics, HFIPS, Chinese Academy of Sciences, Hefei, 230031, P. R. China
- Science Island Branch of Graduate School, University of Science and Technology of China, Hefei, 230026, P. R. China
| | - Yuchen Zhao
- Beijing National Laboratory of Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Liang Si
- School of Physics, Northwest University, Xi'an, 710127, China
| | - Di Tian
- State Key Laboratory of Low Dimensional Quantum Physics and Department of Physics, Tsinghua University, Beijing, 100084, China
| | - Lei Li
- Frontiers Science Center for Flexible Electronics, Xi'an Institute of Flexible Electronics (IFE) and Xi'an Institute of Biomedical Materials and Engineering, Northwestern Polytechnical University, 127 West Youyi Road, Xi'an, 710072, China
| | - Yulin Gan
- Beijing National Laboratory of Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Shaojin Qi
- Beijing National Laboratory of Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Minghang Li
- Beijing National Laboratory of Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Fengxia Hu
- Beijing National Laboratory of Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Jirong Sun
- Beijing National Laboratory of Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Daen Jannis
- Electron Microscopy for Materials Science (EMAT), University of Antwerp, 4Groenenborgerlaan 171, Antwerp, 2020, Belgium
| | - Pu Yu
- State Key Laboratory of Low Dimensional Quantum Physics and Department of Physics, Tsinghua University, Beijing, 100084, China
| | - Gang Chen
- Department of Physics and HKU-UCAS Joint Institute for Theoretical and Computational Physics at Hong Kong, The University of Hong Kong, Hong Kong, 999077, China
| | - Zhicheng Zhong
- CAS Key Laboratory of Magnetic Materials and Devices and Zhejiang Province Key Laboratory of Magnetic Materials and Application Technology, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo, 315201, China
| | - Milan Radovic
- Photon Science Division, Paul Scherrer Institute, Villigen, 5232, Switzerland
| | - Johan Verbeeck
- Electron Microscopy for Materials Science (EMAT), University of Antwerp, 4Groenenborgerlaan 171, Antwerp, 2020, Belgium
| | - Yunzhong Chen
- Beijing National Laboratory of Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Baogen Shen
- Beijing National Laboratory of Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China
- CAS Key Laboratory of Magnetic Materials and Devices and Zhejiang Province Key Laboratory of Magnetic Materials and Application Technology, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo, 315201, China
- Ganjiang Innovation Academy, Chinese Academy of Sciences, Ganzhou, Jiangxi, 341000, China
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2
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Rubano A, Paparo D. Optical Second Harmonic Generation on LaAlO 3/SrTiO 3 Interfaces: A Review. MATERIALS (BASEL, SWITZERLAND) 2023; 16:4337. [PMID: 37374522 DOI: 10.3390/ma16124337] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/20/2023] [Revised: 05/30/2023] [Accepted: 05/31/2023] [Indexed: 06/29/2023]
Abstract
As we approach the limits of semiconductor technology, the development of new materials and technologies for the new era in electronics is compelling. Among others, perovskite oxide hetero-structures are anticipated to be the best candidates. As in the case of semiconductors, the interface between two given materials can have, and often has, very different properties, compared to the corresponding bulk compounds. Perovskite oxides show spectacular interfacial properties due to the the rearrangement of charges, spins, orbitals and the lattice structure itself, at the interface. Lanthanum aluminate and Strontium titanate hetero-structures (LaAlO3/SrTiO3) can be regarded as a prototype of this wider class of interfaces. Both bulk compounds are plain and (relatively) simple wide-bandgap insulators. Despite this, a conductive two-dimensional electron gas (2DEG) is formed right at the interface when a LaAlO3 thickness of n≥4 unit cells is deposited on a SrTiO3 substrate. The 2DEG is quite thin, being confined in only one or at least very few mono-layers at the interface, on the SrTiO3 side. A very intense and long-lasting study was triggered by this surprising discovery. Many questions regarding the origin and characteristics of the two-dimensional electron gas have been (partially) addressed, others are still open. In particular, this includes the interfacial electronic band structure, the transverse plane spatial homogeneity of the samples and the ultrafast dynamics of the confined carriers. Among a very long list of experimental techniques which have been exploited to study these types of interfaces (ARPES, XPS, AFM, PFM, …and many others), optical Second Harmonic Generation (SHG) was found to be suitable for investigating these types of buried interfaces, thanks to its extreme and selective interface-only sensitivity. The SHG technique has made its contribution to the research in this field in a variety of different and important aspects. In this work we will give a bird's eye view of the currently available research on this topic and try to sketch out its future perspectives.
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Affiliation(s)
- Andrea Rubano
- Physics Department "E. Pancini", University Federico II, Monte S. Angelo, Via Cintia, 80126 Naples, Italy
- Institute of Applied Sciences and Intelligent Systems (ISASI), Consiglio Nazionale delle Ricerche (CNR), Via Campi Flegrei 34, 80078 Pozzuoli, Italy
| | - Domenico Paparo
- Institute of Applied Sciences and Intelligent Systems (ISASI), Consiglio Nazionale delle Ricerche (CNR), Via Campi Flegrei 34, 80078 Pozzuoli, Italy
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3
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Liu X, Zhou T, Qin Z, Ma C, Lu F, Liu T, Li J, Wei SH, Cheng G, Liu WT. Nonlinear optical phonon spectroscopy revealing polaronic signatures of the LaAlO 3/SrTiO 3 interface. SCIENCE ADVANCES 2023; 9:eadg7037. [PMID: 37294751 DOI: 10.1126/sciadv.adg7037] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/16/2023] [Accepted: 05/04/2023] [Indexed: 06/11/2023]
Abstract
We report the direct observation of lattice phonons confined at LaAlO3/SrTiO3 (LAO/STO) interfaces and STO surfaces using the sum-frequency phonon spectroscopy. This interface-specific nonlinear optical technique unveiled phonon modes localized within a few monolayers at the interface, with inherent sensitivity to the coupling between lattice and charge degrees of freedom. Spectral evolution across the insulator-to-metal transition at LAO/STO interface revealed an electronic reconstruction at the subcritical LAO thickness, as well as strong polaronic signatures upon formation of the two-dimensional electron gas. We further discovered a characteristic lattice mode from interfacial oxygen vacancies, enabling us to probe such important structural defects in situ. Our study provides a unique perspective on many-body interactions at the correlated oxide interfaces.
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Affiliation(s)
- Xinyi Liu
- Physics Department, State Key Laboratory of Surface Physics, Key Laboratory of Micro and Nano Photonic Structures [Ministry of Education (MOE)], Fudan University, Shanghai 200433, China
| | - Tao Zhou
- Physics Department, State Key Laboratory of Surface Physics, Key Laboratory of Micro and Nano Photonic Structures [Ministry of Education (MOE)], Fudan University, Shanghai 200433, China
| | - Zhiyuan Qin
- CAS Key Laboratory of Microscale Magnetic Resonance and School of Physical Sciences, University of Science and Technology of China, Hefei 230026, China
- Hefei National Laboratory, University of Science and Technology of China, Hefei 230088, China
| | - Changjian Ma
- CAS Key Laboratory of Microscale Magnetic Resonance and School of Physical Sciences, University of Science and Technology of China, Hefei 230026, China
| | - Fanjin Lu
- Physics Department, State Key Laboratory of Surface Physics, Key Laboratory of Micro and Nano Photonic Structures [Ministry of Education (MOE)], Fudan University, Shanghai 200433, China
| | - Tongying Liu
- Physics Department, State Key Laboratory of Surface Physics, Key Laboratory of Micro and Nano Photonic Structures [Ministry of Education (MOE)], Fudan University, Shanghai 200433, China
| | - Jiashi Li
- Physics Department, State Key Laboratory of Surface Physics, Key Laboratory of Micro and Nano Photonic Structures [Ministry of Education (MOE)], Fudan University, Shanghai 200433, China
| | - Su-Huai Wei
- Beijing Computational Science Research Center, Beijing 100193, China
| | - Guanglei Cheng
- CAS Key Laboratory of Microscale Magnetic Resonance and School of Physical Sciences, University of Science and Technology of China, Hefei 230026, China
- Hefei National Laboratory, University of Science and Technology of China, Hefei 230088, China
| | - Wei-Tao Liu
- Physics Department, State Key Laboratory of Surface Physics, Key Laboratory of Micro and Nano Photonic Structures [Ministry of Education (MOE)], Fudan University, Shanghai 200433, China
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4
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Christensen DV. Perspectives on oxide heterostructures - the curious case of γ-Al 2O 3/SrTiO 3. NANOSCALE 2023; 15:3704-3712. [PMID: 36723154 DOI: 10.1039/d2nr07172j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
The heterostructure formed by depositing nanoscale thin films of spinel γ-Al2O3 on perovskite SrTiO3 exhibits a range of exciting properties including room temperature epitaxial growth, high electron mobility, strain-tunable magnetic order, and a symmetry-related reordering of the conduction bands. In comparison to the benchmark LaAlO3/SrTiO3 heterostructure, the γ-Al2O3/SrTiO3 heterostructure has been more sparsely investigated, which leaves plenty of room for scientific and technological discoveries. In this perspective article, I describe the key findings of the γ-Al2O3/SrTiO3 heterostructure and propose five directions for future research: (1) an exploration of novel phenomena emerging when relaxing the conventional epitaxial constraint of matching crystal structures across the interface, (2) a dynamic switching of a strong polarization through nanoscale electromigration of aluminum vacancies, (3) autonomous and forced enhancement of the electron mobility via oxygen vacancy diffusion, (4) writing and erasing of magnetic and conducting nanolines using ferroelastic domain walls, and (5) a multiferroic state formed by combining ferroelectricity, ferromagnetism, and ferroelasticity. The proposed research directions may shed light on both fundamental aspects of the heterostructure and pave the way for applications within green energy devices and nanoelectronics.
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5
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Popescu DG, Husanu MA, Constantinou PC, Filip LD, Trupina L, Bucur CI, Pasuk I, Chirila C, Hrib LM, Stancu V, Pintilie L, Schmitt T, Teodorescu CM, Strocov VN. Experimental Band Structure of Pb(Zr,Ti)O 3 : Mechanism of Ferroelectric Stabilization. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2023; 10:e2205476. [PMID: 36592417 PMCID: PMC9951575 DOI: 10.1002/advs.202205476] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/21/2022] [Revised: 12/07/2022] [Indexed: 06/17/2023]
Abstract
Pb(Zr,Ti)O3 (PZT) is the most common ferroelectric (FE) material widely used in solid-state technology. Despite intense studies of PZT over decades, its intrinsic band structure, electron energy depending on 3D momentum k, is still unknown. Here, Pb(Zr0.2 Ti0.8 )O3 using soft-X-ray angle-resolved photoelectron spectroscopy (ARPES) is explored. The enhanced photoelectron escape depth in this photon energy range allows sharp intrinsic definition of the out-of-plane momentum k and thereby of the full 3D band structure. Furthermore, the problem of sample charging due to the inherently insulating nature of PZT is solved by using thin-film PZT samples, where a thickness-induced self-doping results in their heavy doping. For the first time, the soft-X-ray ARPES experiments deliver the intrinsic 3D band structure of PZT as well as the FE-polarization dependent electrostatic potential profile across the PZT film deposited on SrTiO3 and Lax SrMn1- x O3 substrates. The negative charges near the surface, required to stabilize the FE state pointing away from the sample (P+), are identified as oxygen vacancies creating localized in-gap states below the Fermi energy. For the opposite polarization state (P-), the positive charges near the surface are identified as cation vacancies resulting from non-ideal stoichiometry of the PZT film as deduced from quantitative XPS measurements.
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Affiliation(s)
| | | | | | - Lucian Dragos Filip
- National Institute of Materials PhysicsAtomistilor 405AMagurele077125Romania
| | - Lucian Trupina
- National Institute of Materials PhysicsAtomistilor 405AMagurele077125Romania
| | | | - Iuliana Pasuk
- National Institute of Materials PhysicsAtomistilor 405AMagurele077125Romania
| | - Cristina Chirila
- National Institute of Materials PhysicsAtomistilor 405AMagurele077125Romania
| | | | - Viorica Stancu
- National Institute of Materials PhysicsAtomistilor 405AMagurele077125Romania
| | - Lucian Pintilie
- National Institute of Materials PhysicsAtomistilor 405AMagurele077125Romania
| | - Thorsten Schmitt
- Swiss Light SourcePaul Scherrer InstituteVilligen‐PSI5232Switzerland
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6
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Lafuente-Bartolome J, Lian C, Sio WH, Gurtubay IG, Eiguren A, Giustino F. Unified Approach to Polarons and Phonon-Induced Band Structure Renormalization. PHYSICAL REVIEW LETTERS 2022; 129:076402. [PMID: 36018689 DOI: 10.1103/physrevlett.129.076402] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/08/2022] [Accepted: 07/12/2022] [Indexed: 06/15/2023]
Abstract
Ab initio calculations of the phonon-induced band structure renormalization are currently based on the perturbative Allen-Heine theory and its many-body generalizations. These approaches are unsuitable to describe materials where electrons form localized polarons. Here, we develop a self-consistent, many-body Green's function theory of band structure renormalization that incorporates localization and self-trapping. We show that the present approach reduces to the Allen-Heine theory in the weak-coupling limit, and to total energy calculations of self-trapped polarons in the strong-coupling limit. To demonstrate this methodology, we reproduce the path-integral results of Feynman and diagrammatic Monte Carlo calculations for the Fröhlich model at all couplings, and we calculate the zero point renormalization of the band gap of an ionic insulator including polaronic effects.
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Affiliation(s)
- Jon Lafuente-Bartolome
- Oden Institute for Computational Engineering and Sciences, The University of Texas at Austin, Austin, Texas 78712, USA
- Department of Physics, The University of Texas at Austin, Austin, Texas 78712, USA
| | - Chao Lian
- Oden Institute for Computational Engineering and Sciences, The University of Texas at Austin, Austin, Texas 78712, USA
- Department of Physics, The University of Texas at Austin, Austin, Texas 78712, USA
| | - Weng Hong Sio
- Institute of Applied Physics and Materials Engineering, University of Macau, Macao SAR 999078, People's Republic of China
| | - Idoia G Gurtubay
- Fisika Saila, University of the Basque Country UPV/EHU, 48080 Bilbao, Basque Country, Spain
- Donostia International Physics Center (DIPC), Paseo Manuel de Lardizabal 4, 20018 Donostia-San Sebastián, Spain
- EHU Quantum Center, University of the Basque Country UPV/EHU, Barrio Sarriena, s/n, 48940 Leioa, Biscay, Spain
| | - Asier Eiguren
- Fisika Saila, University of the Basque Country UPV/EHU, 48080 Bilbao, Basque Country, Spain
- Donostia International Physics Center (DIPC), Paseo Manuel de Lardizabal 4, 20018 Donostia-San Sebastián, Spain
- EHU Quantum Center, University of the Basque Country UPV/EHU, Barrio Sarriena, s/n, 48940 Leioa, Biscay, Spain
| | - Feliciano Giustino
- Oden Institute for Computational Engineering and Sciences, The University of Texas at Austin, Austin, Texas 78712, USA
- Department of Physics, The University of Texas at Austin, Austin, Texas 78712, USA
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7
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Abstract
Mechanistic studies on lead halide perovskites (LHPs) in recent years have suggested charge carrier screening as partially responsible for long carrier diffusion lengths and lifetimes that are key to superior optoelectronic properties. These findings have led to the ferroelectric large polaron proposal, which attributes efficient charge carrier screening to the extended ordering of dipoles from symmetry-breaking unit cells that undergo local structural distortion and break inversion symmetry. It remains an open question whether this proposal applies in general to semiconductors with LHP-like anharmonic and dynamically disordered phonons. Here, we study electron-phonon coupling in Bi2O2Se, a semiconductor which bears resemblance to LHPs in ionic bonding, spin-orbit coupling, band transport with long carrier diffusion lengths and lifetimes, and phonon disorder as revealed by temperature-dependent Raman spectroscopy. Using coherent phonon spectroscopy, we show the strong coupling of an anharmonic phonon mode at 1.50 THz to photo-excited charge carriers, while the Raman excitation of this mode is symmetry-forbidden in the ground-state. Density functional theory calculations show that this mode, originating from the A1g phonon of out-of-plane Bi/Se motion, gains oscillator strength from symmetry-lowering in polaron formation. Specifically, lattice distortion upon ultrafast charge localization results in extended ordering of symmetry-breaking unit cells and a planar polaron wavefunction, namely a two-dimensional polaron in a three-dimensional lattice. This study provides experimental and theoretical insights into charge interaction with anharmonic phonons in Bi2O2Se and suggests ferroelectric polaron formation may be a general principle for efficient charge carrier screening and for defect-tolerant semiconductors.
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8
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Reticcioli M, Wang Z, Schmid M, Wrana D, Boatner LA, Diebold U, Setvin M, Franchini C. Competing electronic states emerging on polar surfaces. Nat Commun 2022; 13:4311. [PMID: 35879300 PMCID: PMC9314351 DOI: 10.1038/s41467-022-31953-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2021] [Accepted: 07/07/2022] [Indexed: 11/28/2022] Open
Abstract
Excess charge on polar surfaces of ionic compounds is commonly described by the two-dimensional electron gas (2DEG) model, a homogeneous distribution of charge, spatially-confined in a few atomic layers. Here, by combining scanning probe microscopy with density functional theory calculations, we show that excess charge on the polar TaO2 termination of KTaO3(001) forms more complex electronic states with different degrees of spatial and electronic localization: charge density waves (CDW) coexist with strongly-localized electron polarons and bipolarons. These surface electronic reconstructions, originating from the combined action of electron-lattice interaction and electronic correlation, are energetically more favorable than the 2DEG solution. They exhibit distinct spectroscopy signals and impact on the surface properties, as manifested by a local suppression of ferroelectric distortions.
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Affiliation(s)
- Michele Reticcioli
- University of Vienna, Faculty of Physics, Center for Computational Materials Science, Vienna, Austria
- Institute of Applied Physics, Technische Universität Wien, Vienna, Austria
| | - Zhichang Wang
- Institute of Applied Physics, Technische Universität Wien, Vienna, Austria
- State Key Laboratory for Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy Materials, and Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, China
| | - Michael Schmid
- Institute of Applied Physics, Technische Universität Wien, Vienna, Austria
| | - Dominik Wrana
- Department of Surface and Plasma Science, Faculty of Mathematics and Physics, Charles University, 180 00, Prague 8, Czech Republic
| | - Lynn A Boatner
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA
| | - Ulrike Diebold
- Institute of Applied Physics, Technische Universität Wien, Vienna, Austria
| | - Martin Setvin
- Institute of Applied Physics, Technische Universität Wien, Vienna, Austria.
- Department of Surface and Plasma Science, Faculty of Mathematics and Physics, Charles University, 180 00, Prague 8, Czech Republic.
| | - Cesare Franchini
- University of Vienna, Faculty of Physics, Center for Computational Materials Science, Vienna, Austria.
- Dipartimento di Fisica e Astronomia, Università di Bologna, 40127, Bologna, Italy.
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9
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Yu T, Wright J, Khalsa G, Pamuk B, Chang CS, Matveyev Y, Wang X, Schmitt T, Feng D, Muller DA, Xing HG, Jena D, Strocov VN. Momentum-resolved electronic structure and band offsets in an epitaxial NbN/GaN superconductor/semiconductor heterojunction. SCIENCE ADVANCES 2021; 7:eabi5833. [PMID: 34936435 PMCID: PMC8694612 DOI: 10.1126/sciadv.abi5833] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/21/2021] [Accepted: 11/05/2021] [Indexed: 06/14/2023]
Abstract
The electronic structure of heterointerfaces is a pivotal factor for their device functionality. We use soft x-ray angle-resolved photoelectron spectroscopy to directly measure the momentum-resolved electronic band structures on both sides of the Schottky heterointerface formed by epitaxial films of the superconducting NbN on semiconducting GaN, and determine their momentum-dependent interfacial band offset as well as the band-bending profile. We find, in particular, that the Fermi states in NbN are well separated in energy and momentum from the states in GaN, excluding any notable electronic cross-talk of the superconducting states in NbN to GaN. We support the experimental findings with first-principles calculations for bulk NbN and GaN. The Schottky barrier height obtained from photoemission is corroborated by electronic transport and optical measurements. The momentum-resolved understanding of electronic properties of interfaces elucidated in our work opens up new frontiers for the quantum materials where interfacial states play a defining role.
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Affiliation(s)
- Tianlun Yu
- Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
- Advanced Materials Laboratory, State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China
| | - John Wright
- Materials Science and Engineering, Cornell University, Ithaca, NY 14850, USA
| | - Guru Khalsa
- Materials Science and Engineering, Cornell University, Ithaca, NY 14850, USA
| | - Betül Pamuk
- Platform for the Accelerated Realization, Analysis, and Discovery of Interface Materials (PARADIM), Cornell University, Ithaca, NY 14853, USA
| | - Celesta S. Chang
- School of Applied and Engineering Physics, Cornell University, Ithaca, NY 14853, USA
| | - Yury Matveyev
- Photon Science, Deutsches Elektronen-Synchrotron DESY, Notkestr. 85, 22607 Hamburg, Germany
| | - Xiaoqiang Wang
- Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
| | - Thorsten Schmitt
- Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
| | - Donglai Feng
- Shanghai Research Center for Quantum Sciences, Shanghai 201315, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing 210093, China
- Hefei National Laboratory for Physical Science at Microscale, CAS Center for Excellence in Quantum Information and Quantum Physics, and Department of Physics, University of Science and Technology of China, Hefei 230026, China
| | - David A. Muller
- School of Applied and Engineering Physics, Cornell University, Ithaca, NY 14853, USA
- Kavli Institute at Cornell for Nanoscale Science, Cornell University, Ithaca, NY 14853, USA
| | - Huili Grace Xing
- Kavli Institute at Cornell for Nanoscale Science, Cornell University, Ithaca, NY 14853, USA
- Electrical and Computer Engineering and Materials Science and Engineering, Cornell University, Ithaca, NY 14853, USA
| | - Debdeep Jena
- Kavli Institute at Cornell for Nanoscale Science, Cornell University, Ithaca, NY 14853, USA
- Electrical and Computer Engineering and Materials Science and Engineering, Cornell University, Ithaca, NY 14853, USA
| | - Vladimir N. Strocov
- Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
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10
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Kimura M, He X, Katase T, Tadano T, Tomczak JM, Minohara M, Aso R, Yoshida H, Ide K, Ueda S, Hiramatsu H, Kumigashira H, Hosono H, Kamiya T. Large phonon drag thermopower boosted by massive electrons and phonon leaking in LaAlO 3/LaNiO 3/LaAlO 3 heterostructure. NANO LETTERS 2021; 21:9240-9246. [PMID: 34709840 PMCID: PMC8587880 DOI: 10.1021/acs.nanolett.1c03143] [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: 08/16/2021] [Revised: 10/11/2021] [Indexed: 06/04/2023]
Abstract
An unusually large thermopower (S) enhancement is induced by heterostructuring thin films of the strongly correlated electron oxide LaNiO3. The phonon-drag effect, which is not observed in bulk LaNiO3, enhances S for thin films compressively strained by LaAlO3 substrates. By a reduction in the layer thickness down to three unit cells and subsequent LaAlO3 surface termination, a 10 times S enhancement over the bulk value is observed due to large phonon drag S (Sg), and the Sg contribution to the total S occurs over a much wider temperature range up to 220 K. The Sg enhancement originates from the coupling of lattice vibration to the d electrons with large effective mass in the compressively strained ultrathin LaNiO3, and the electron-phonon interaction is largely enhanced by the phonon leakage from the LaAlO3 substrate and the capping layer. The transition-metal oxide heterostructures emerge as a new playground to manipulate electronic and phononic properties in the quest for high-performance thermoelectrics.
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Affiliation(s)
- Masatoshi Kimura
- Laboratory
for Materials and Structures, Institute of Innovative Research, Tokyo Institute of Technology, 4259 Nagatsuta, Midori, Yokohama 226-8503, Japan
| | - Xinyi He
- Laboratory
for Materials and Structures, Institute of Innovative Research, Tokyo Institute of Technology, 4259 Nagatsuta, Midori, Yokohama 226-8503, Japan
| | - Takayoshi Katase
- Laboratory
for Materials and Structures, Institute of Innovative Research, Tokyo Institute of Technology, 4259 Nagatsuta, Midori, Yokohama 226-8503, Japan
- PRESTO,
Japan Science and Technology Agency, 7 Gobancho, Chiyoda, Tokyo 102-0076, Japan
| | - Terumasa Tadano
- National
Institute for Materials Science, Sengen, Tsukuba 305-0047, Japan
| | - Jan M. Tomczak
- Institute
of Solid State Physics, Vienna University
of Technology, Wiedner Hauptstrasse 8-10, A-1040 Vienna, Austria
| | - Makoto Minohara
- Research
Institute for Advanced Electronics and Photonics, National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki 305-8568, Japan
| | - Ryotaro Aso
- Department
of Applied Quantum Physics and Nuclear Engineering, Kyushu University, Fukuoka, Fukuoka 819-0395, Japan
| | - Hideto Yoshida
- The
Institute of Scientific and Industrial Research, Osaka University, 8-1 Mihogaoka, Ibaraki, Osaka 567-0047, Japan
| | - Keisuke Ide
- Laboratory
for Materials and Structures, Institute of Innovative Research, Tokyo Institute of Technology, 4259 Nagatsuta, Midori, Yokohama 226-8503, Japan
| | - Shigenori Ueda
- Research
Center for Functional Materials, National
Institute for Materials Science, Namiki, Tsukuba 305-0044, Japan
- Research
Center for Advanced Measurement and Characterization, National Institute for Materials Science, Tsukuba 305-0047, Japan
- Synchrotron
X-ray Station at SPring-8, National Institute
for Materials Science, 1-1-1 Sayo, Hyogo, 679-5148, Japan
| | - Hidenori Hiramatsu
- Laboratory
for Materials and Structures, Institute of Innovative Research, Tokyo Institute of Technology, 4259 Nagatsuta, Midori, Yokohama 226-8503, Japan
- Materials
Research Center for Element Strategy, Tokyo
Institute of Technology, 4259 Nagatsuta, Midori, Yokohama 226-8503, Japan
| | - Hiroshi Kumigashira
- Photon
Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization, Tsukuba, Ibaraki 305-0801, Japan
- Institute
of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai 980-8577, Japan
| | - Hideo Hosono
- Materials
Research Center for Element Strategy, Tokyo
Institute of Technology, 4259 Nagatsuta, Midori, Yokohama 226-8503, Japan
| | - Toshio Kamiya
- Laboratory
for Materials and Structures, Institute of Innovative Research, Tokyo Institute of Technology, 4259 Nagatsuta, Midori, Yokohama 226-8503, Japan
- Materials
Research Center for Element Strategy, Tokyo
Institute of Technology, 4259 Nagatsuta, Midori, Yokohama 226-8503, Japan
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11
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Kang L, Du X, Zhou JS, Gu X, Chen YJ, Xu RZ, Zhang QQ, Sun SC, Yin ZX, Li YW, Pei D, Zhang J, Gu RK, Wang ZG, Liu ZK, Xiong R, Shi J, Zhang Y, Chen YL, Yang LX. Band-selective Holstein polaron in Luttinger liquid material A 0.3MoO 3 (A = K, Rb). Nat Commun 2021; 12:6183. [PMID: 34702828 PMCID: PMC8548323 DOI: 10.1038/s41467-021-26078-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2021] [Accepted: 09/14/2021] [Indexed: 11/09/2022] Open
Abstract
(Quasi-)one-dimensional systems exhibit various fascinating properties such as Luttinger liquid behavior, Peierls transition, novel topological phases, and the accommodation of unique quasiparticles (e.g., spinon, holon, and soliton, etc.). Here we study molybdenum blue bronze A0.3MoO3 (A = K, Rb), a canonical quasi-one-dimensional charge-density-wave material, using laser-based angle-resolved photoemission spectroscopy. Our experiment suggests that the normal phase of A0.3MoO3 is a prototypical Luttinger liquid, from which the charge-density-wave emerges with decreasing temperature. Prominently, we observe strong renormalizations of band dispersions, which are recognized as the spectral function of Holstein polaron derived from band-selective electron-phonon coupling in the system. We argue that the strong electron-phonon coupling plays an important role in electronic properties and the charge-density-wave transition in blue bronzes. Our results not only reconcile the long-standing heavy debates on the electronic properties of blue bronzes but also provide a rare platform to study interesting excitations in Luttinger liquid materials.
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Affiliation(s)
- L Kang
- State Key Laboratory of Low Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing, 100084, China
| | - X Du
- State Key Laboratory of Low Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing, 100084, China
| | - J S Zhou
- State Key Laboratory of Low Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing, 100084, China
| | - X Gu
- State Key Laboratory of Low Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing, 100084, China
| | - Y J Chen
- State Key Laboratory of Low Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing, 100084, China
| | - R Z Xu
- State Key Laboratory of Low Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing, 100084, China
| | - Q Q Zhang
- State Key Laboratory of Low Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing, 100084, China
| | - S C Sun
- State Key Laboratory of Low Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing, 100084, China
| | - Z X Yin
- State Key Laboratory of Low Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing, 100084, China
| | - Y W Li
- School of Physical Science and Technology, ShanghaiTech University and CAS-Shanghai Science Research Center, Shanghai, 201210, China.,ShanghaiTech Laboratory for Topological Physics, Shanghai, 200031, China
| | - D Pei
- Department of Physics, Clarendon Laboratory, University of Oxford, Oxford, OX1 3PU, UK
| | - J Zhang
- School of Physical Science and Technology, ShanghaiTech University and CAS-Shanghai Science Research Center, Shanghai, 201210, China
| | - R K Gu
- Department of Physics, Clarendon Laboratory, University of Oxford, Oxford, OX1 3PU, UK
| | - Z G Wang
- International Center for Quantum Materials, School of Physics, Peking University, Beijing, 100871, China
| | - Z K Liu
- School of Physical Science and Technology, ShanghaiTech University and CAS-Shanghai Science Research Center, Shanghai, 201210, China.,ShanghaiTech Laboratory for Topological Physics, Shanghai, 200031, China
| | - R Xiong
- Department of Physics, Wuhan University, Wuhan, 430072, China
| | - J Shi
- Department of Physics, Wuhan University, Wuhan, 430072, China
| | - Y Zhang
- International Center for Quantum Materials, School of Physics, Peking University, Beijing, 100871, China
| | - Y L Chen
- State Key Laboratory of Low Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing, 100084, China. .,School of Physical Science and Technology, ShanghaiTech University and CAS-Shanghai Science Research Center, Shanghai, 201210, China. .,ShanghaiTech Laboratory for Topological Physics, Shanghai, 200031, China. .,Department of Physics, Clarendon Laboratory, University of Oxford, Oxford, OX1 3PU, UK.
| | - L X Yang
- State Key Laboratory of Low Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing, 100084, China. .,Frontier Science Center for Quantum Information, Beijing, 100084, China.
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12
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Extremely low-energy ARPES of quantum well states in cubic-GaN/AlN and GaAs/AlGaAs heterostructures. Sci Rep 2021; 11:19081. [PMID: 34580361 PMCID: PMC8476498 DOI: 10.1038/s41598-021-98569-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2021] [Accepted: 08/25/2021] [Indexed: 11/30/2022] Open
Abstract
Quantum well (QW) heterostructures have been extensively used for the realization of a wide range of optical and electronic devices. Exploiting their potential for further improvement and development requires a fundamental understanding of their electronic structure. So far, the most commonly used experimental techniques for this purpose have been all-optical spectroscopy methods that, however, are generally averaging in momentum space. Additional information can be gained by angle-resolved photoelectron spectroscopy (ARPES), which measures the electronic structure with momentum resolution. Here we report on the use of extremely low-energy ARPES (photon energy ~ 7 eV) to increase depth sensitivity and access buried QW states, located at 3 nm and 6 nm below the surface of cubic-GaN/AlN and GaAs/AlGaAs heterostructures, respectively. We find that the QW states in cubic-GaN/AlN can indeed be observed, but not their energy dispersion, because of the high surface roughness. The GaAs/AlGaAs QW states, on the other hand, are buried too deep to be detected by extremely low-energy ARPES. Since the sample surface is much flatter, the ARPES spectra of the GaAs/AlGaAs show distinct features in momentum space, which can be reconducted to the band structure of the topmost surface layer of the QW structure. Our results provide important information about the samples’ properties required to perform extremely low-energy ARPES experiments on electronic states buried in semiconductor heterostructures.
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13
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Leermakers I, Rubi K, Yang M, Kerdi B, Goiran M, Escoffier W, Rana AS, Smink AEM, Brinkman A, Hilgenkamp H, Maan JC, Zeitler U. Quantum oscillations in an optically-illuminated two-dimensional electron system at the LaAlO 3/SrTiO 3interface. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2021; 33:465002. [PMID: 34433152 DOI: 10.1088/1361-648x/ac211a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/26/2021] [Accepted: 08/25/2021] [Indexed: 06/13/2023]
Abstract
We have investigated the illumination effect on the magnetotransport properties of a two-dimensional electron system at the LaAlO3/SrTiO3interface. The illumination significantly reduces the zero-field sheet resistance, eliminates the Kondo effect at low-temperature, and switches the negative magnetoresistance into the positive one. A large increase in the density of high-mobility carriers after illumination leads to quantum oscillations in the magnetoresistance originating from the Landau quantization. The carrier density (∼2 × 1012 cm-2) and effective mass (∼1.7me) estimated from the oscillations suggest that the high-mobility electrons occupy thedxz/yzsubbands of Ti:t2gorbital extending deep within the conducting sheet of SrTiO3. Our results demonstrate that the illumination which induces additional carriers at the interface can pave the way to control the Kondo-like scattering and study the quantum transport in the complex oxide heterostructures.
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Affiliation(s)
- I Leermakers
- High Field Magnet Laboratory (HFML-EMFL) and Institute for Molecules and Materials, Radboud University, Nijmegen, The Netherlands
| | - K Rubi
- High Field Magnet Laboratory (HFML-EMFL) and Institute for Molecules and Materials, Radboud University, Nijmegen, The Netherlands
| | - M Yang
- Laboratoire National des Champs Magnétiques Intenses (LNCMI-EMFL), Université de Toulouse, CNRS, INSA, UPS, 143 Avenue de Rangueil, 31400 Toulouse, France
| | - B Kerdi
- Laboratoire National des Champs Magnétiques Intenses (LNCMI-EMFL), Université de Toulouse, CNRS, INSA, UPS, 143 Avenue de Rangueil, 31400 Toulouse, France
| | - M Goiran
- Laboratoire National des Champs Magnétiques Intenses (LNCMI-EMFL), Université de Toulouse, CNRS, INSA, UPS, 143 Avenue de Rangueil, 31400 Toulouse, France
| | - W Escoffier
- Laboratoire National des Champs Magnétiques Intenses (LNCMI-EMFL), Université de Toulouse, CNRS, INSA, UPS, 143 Avenue de Rangueil, 31400 Toulouse, France
| | - A S Rana
- MESA + Institute for Nanotechnology, University of Twente, PO Box 217, 7500 AE Enschede, The Netherlands
| | - A E M Smink
- MESA + Institute for Nanotechnology, University of Twente, PO Box 217, 7500 AE Enschede, The Netherlands
| | - A Brinkman
- MESA + Institute for Nanotechnology, University of Twente, PO Box 217, 7500 AE Enschede, The Netherlands
| | - H Hilgenkamp
- MESA + Institute for Nanotechnology, University of Twente, PO Box 217, 7500 AE Enschede, The Netherlands
| | - J C Maan
- High Field Magnet Laboratory (HFML-EMFL) and Institute for Molecules and Materials, Radboud University, Nijmegen, The Netherlands
| | - U Zeitler
- High Field Magnet Laboratory (HFML-EMFL) and Institute for Molecules and Materials, Radboud University, Nijmegen, The Netherlands
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14
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Fang L, Chen C, Sundaresan A, Narayana C, Ter-Oganessian N, Pyatakov AP, Cao S, Zhang J, Ren W. The CdTiO 3/BaTiO 3 superlattice interface from first principles. NANOSCALE 2021; 13:8506-8513. [PMID: 33904555 DOI: 10.1039/d1nr00374g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
The oxide interface has been studied extensively in the past decades and exhibits different physical properties from the constituent bulks. Using first-principles electronic structure calculations, we investigated the interface of CdTiO3/BaTiO3 (CTO/BTO) superlattice with ferroelectric BaTiO3. In this case, the conduction bands of CdTiO3 are composed of Cd-5s orbitals with low electron effective mass and nondegenerate dispersion, and thus expected to have high mobility. We predicted a controllable conductivity at the interface, and further analyzed how the polarization direction and strength affect the conductivity. We also explored the relationship between two components: thickness and polarization. Intriguingly, the total polarization in CTO/BTO might be even larger than that of ferroelectric bulk BaTiO3. Therefore, we found a way to maximize the superlattice polarization by increasing the fraction of the CdTiO3 layers, based on the interesting dependence of the total polarization and CTO/BTO ratio.
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Affiliation(s)
- Le Fang
- Materials Genome Institute, International Center for Quantum and Molecular Structures, Shanghai University, Shanghai 200444, China.
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15
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Chikina A, Christensen DV, Borisov V, Husanu MA, Chen Y, Wang X, Schmitt T, Radovic M, Nagaosa N, Mishchenko AS, Valentí R, Pryds N, Strocov VN. Band-Order Anomaly at the γ-Al 2O 3/SrTiO 3 Interface Drives the Electron-Mobility Boost. ACS NANO 2021; 15:4347-4356. [PMID: 33661601 DOI: 10.1021/acsnano.0c07609] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
The rich functionalities of transition-metal oxides and their interfaces bear an enormous technological potential. Its realization in practical devices requires, however, a significant improvement of yet relatively low electron mobility in oxide materials. Recently, a mobility boost of about 2 orders of magnitude has been demonstrated at the spinel-perovskite γ-Al2O3/SrTiO3 interface compared to the paradigm perovskite-perovskite LaAlO3/SrTiO3 interface. We explore the fundamental physics behind this phenomenon from direct measurements of the momentum-resolved electronic structure of this interface using resonant soft-X-ray angle-resolved photoemission. We find an anomaly in orbital ordering of the mobile electrons in γ-Al2O3/SrTiO3 which depopulates electron states in the top SrTiO3 layer. This rearrangement of the mobile electron system pushes the electron density away from the interface, which reduces its overlap with the interfacial defects and weakens the electron-phonon interaction, both effects contributing to the mobility boost. A crystal-field analysis shows that the band order alters owing to the symmetry breaking between the spinel γ-Al2O3 and perovskite SrTiO3. Band-order engineering, exploiting the fundamental symmetry properties, emerges as another route to boost the performance of oxide devices.
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Affiliation(s)
- Alla Chikina
- Swiss Light Source, Paul Scherrer Institute, 5232 Villigen-PSI, Switzerland
- Institute of Physics and Astronomy, Aarhus University, Ny Munkegade 120, 8000 Aarhus, Denmark
| | - Dennis V Christensen
- Department of Energy Conversion and Storage, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark
| | - Vladislav Borisov
- Institut für Theoretische Physik, Goethe-Universität Frankfurt am Main, Max-von-Laue-Strasse 1, 60438 Frankfurt am Main, Germany
- Department of Physics and Astronomy, Uppsala University, Box 516, 5120 Uppsala, Sweden
| | - Marius-Adrian Husanu
- Swiss Light Source, Paul Scherrer Institute, 5232 Villigen-PSI, Switzerland
- National Institute of Materials Physics, Atomistilor 405A, 077125 Magurele, Romania
| | - Yunzhong Chen
- Department of Energy Conversion and Storage, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Xiaoqiang Wang
- Swiss Light Source, Paul Scherrer Institute, 5232 Villigen-PSI, Switzerland
| | - Thorsten Schmitt
- Swiss Light Source, Paul Scherrer Institute, 5232 Villigen-PSI, Switzerland
| | - Milan Radovic
- Swiss Light Source, Paul Scherrer Institute, 5232 Villigen-PSI, Switzerland
| | - Naoto Nagaosa
- RIKEN Center for Emergent Matter Science, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
- Department of Applied Physics, University of Tokyo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - Andrey S Mishchenko
- RIKEN Center for Emergent Matter Science, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - Roser Valentí
- Institut für Theoretische Physik, Goethe-Universität Frankfurt am Main, Max-von-Laue-Strasse 1, 60438 Frankfurt am Main, Germany
| | - Nini Pryds
- Department of Energy Conversion and Storage, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark
| | - Vladimir N Strocov
- Swiss Light Source, Paul Scherrer Institute, 5232 Villigen-PSI, Switzerland
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16
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Han TT, Chen L, Cai C, Wang ZG, Wang YD, Xin ZM, Zhang Y. Metal-Insulator Transition and Emergent Gapped Phase in the Surface-Doped 2D Semiconductor 2H-MoTe_{2}. PHYSICAL REVIEW LETTERS 2021; 126:106602. [PMID: 33784141 DOI: 10.1103/physrevlett.126.106602] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/21/2020] [Accepted: 02/17/2021] [Indexed: 06/12/2023]
Abstract
Artificially created two-dimensional (2D) interfaces or structures are ideal for seeking exotic phase transitions due to their highly tunable carrier density and interfacially enhanced many-body interactions. Here, we report the discovery of a metal-insulator transition (MIT) and an emergent gapped phase in the metal-semiconductor interface that is created in 2H-MoTe_{2} via alkali-metal deposition. Using angle-resolved photoemission spectroscopy, we found that the electron-phonon coupling is strong at the interface as characterized by a clear observation of replica shake-off bands. Such strong electron-phonon coupling interplays with disorder scattering, leading to an Anderson localization of polarons which could explain the MIT. The domelike emergent gapped phase could then be attributed to a polaron extended state or phonon-mediated superconductivity. Our results demonstrate the capability of alkali-metal deposition as an effective method to enhance the many-body interactions in 2D semiconductors. The surface-doped 2H-MoTe_{2} is a promising candidate for realizing polaronic insulator and high-T_{c} superconductivity.
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Affiliation(s)
- T T Han
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
| | - L Chen
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
| | - C Cai
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
| | - Z G Wang
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
| | - Y D Wang
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
| | - Z M Xin
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
| | - Y Zhang
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
- Collaborative Innovation Center of Quantum Matter, Beijing 100871, China
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17
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King PDC, Picozzi S, Egdell RG, Panaccione G. Angle, Spin, and Depth Resolved Photoelectron Spectroscopy on Quantum Materials. Chem Rev 2021; 121:2816-2856. [PMID: 33346644 DOI: 10.1021/acs.chemrev.0c00616] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The role of X-ray based electron spectroscopies in determining chemical, electronic, and magnetic properties of solids has been well-known for several decades. A powerful approach is angle-resolved photoelectron spectroscopy, whereby the kinetic energy and angle of photoelectrons emitted from a sample surface are measured. This provides a direct measurement of the electronic band structure of crystalline solids. Moreover, it yields powerful insights into the electronic interactions at play within a material and into the control of spin, charge, and orbital degrees of freedom, central pillars of future solid state science. With strong recent focus on research of lower-dimensional materials and modified electronic behavior at surfaces and interfaces, angle-resolved photoelectron spectroscopy has become a core technique in the study of quantum materials. In this review, we provide an introduction to the technique. Through examples from several topical materials systems, including topological insulators, transition metal dichalcogenides, and transition metal oxides, we highlight the types of information which can be obtained. We show how the combination of angle, spin, time, and depth-resolved experiments are able to reveal "hidden" spectral features, connected to semiconducting, metallic and magnetic properties of solids, as well as underlining the importance of dimensional effects in quantum materials.
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Affiliation(s)
- Phil D C King
- SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews KY16 9SS, United Kingdom
| | - Silvia Picozzi
- Consiglio Nazionale delle Ricerche, CNR-SPIN, Via dei Vestini 31, Chieti 66100, Italy
| | - Russell G Egdell
- Department of Chemistry, Inorganic Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QR, United Kingdom
| | - Giancarlo Panaccione
- Istituto Officina dei Materiali (IOM)-CNR, Laboratorio TASC, in Area Science Park, S.S.14, Km 163.5, I-34149 Trieste, Italy
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18
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Hydride-based antiperovskites with soft anionic sublattices as fast alkali ionic conductors. Nat Commun 2021; 12:201. [PMID: 33420012 PMCID: PMC7794446 DOI: 10.1038/s41467-020-20370-2] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2020] [Accepted: 11/27/2020] [Indexed: 11/09/2022] Open
Abstract
Most solid-state materials are composed of p-block anions, only in recent years the introduction of hydride anions (1s2) in oxides (e.g., SrVO2H, BaTi(O,H)3) has allowed the discovery of various interesting properties. Here we exploit the large polarizability of hydride anions (H-) together with chalcogenide (Ch2-) anions to construct a family of antiperovskites with soft anionic sublattices. The M3HCh antiperovskites (M = Li, Na) adopt the ideal cubic structure except orthorhombic Na3HS, despite the large variation in sizes of M and Ch. This unconventional robustness of cubic phase mainly originates from the large size-flexibility of the H- anion. Theoretical and experimental studies reveal low migration barriers for Li+/Na+ transport and high ionic conductivity, possibly promoted by a soft phonon mode associated with the rotational motion of HM6 octahedra in their cubic forms. Aliovalent substitution to create vacancies has further enhanced ionic conductivities of this series of antiperovskites, resulting in Na2.9H(Se0.9I0.1) achieving a high conductivity of ~1 × 10-4 S/cm (100 °C).
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19
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Mao Y, Ma X, Wu D, Lin C, Shan H, Wu X, Zhao J, Zhao A, Wang B. Interfacial Polarons in van der Waals Heterojunction of Monolayer SnSe 2 on SrTiO 3 (001). NANO LETTERS 2020; 20:8067-8073. [PMID: 33044080 DOI: 10.1021/acs.nanolett.0c02741] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Interfacial polarons have been demonstrated to play important roles in heterostructures containing polar substrates. However, most of polarons found so far are diffusive large polarons; the discovery and investigation of small polarons at interfaces are scarce. Herein, we report the emergence of interfacial polarons in monolayer SnSe2 epitaxially grown on Nb-doped SrTiO3 (STO) surface using angle-resolved photoemission spectroscopy (ARPES) and scanning tunneling microscopy (STM). ARPES spectra taken on this heterointerface reveal a nearly flat in-gap band correlated with a significant charge modulation in real space as observed with STM. An interfacial polaronic model is proposed to ascribe this in-gap band to the formation of self-trapped small polarons induced by charge accumulation and electron-phonon coupling at the van der Waals interface of SnSe2 and STO. Such a mechanism to form interfacial polaron is expected to generally exist in similar van der Waals heterojunctions consisting of layered 2D materials and polar substrates.
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Affiliation(s)
- Yahui Mao
- Hefei National Laboratory for Physical Sciences at the Microscale and Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Xiaochuan Ma
- Hefei National Laboratory for Physical Sciences at the Microscale and Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Daoxiong Wu
- CAS Key Laboratory of Materials for Energy Conservation, CAS Center for Excellence in Nanoscience, and Department of Material Science and Engineering, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Chen Lin
- Hefei National Laboratory for Physical Sciences at the Microscale and Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Huan Shan
- Hefei National Laboratory for Physical Sciences at the Microscale and Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Xiaojun Wu
- Hefei National Laboratory for Physical Sciences at the Microscale and Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
- CAS Key Laboratory of Materials for Energy Conservation, CAS Center for Excellence in Nanoscience, and Department of Material Science and Engineering, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Jin Zhao
- Hefei National Laboratory for Physical Sciences at the Microscale and Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
- ICQD and CAS Key Laboratory of Strongly-Coupled Quantum Matter Physics, and Department of Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Aidi Zhao
- Hefei National Laboratory for Physical Sciences at the Microscale and Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
- School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, China
| | - Bing Wang
- Hefei National Laboratory for Physical Sciences at the Microscale and Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
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20
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Zwiebler M, Di Gennaro E, Hamann-Borrero JE, Ritschel T, Green RJ, Sawatzky GA, Schierle E, Weschke E, Leo A, Granozio FM, Geck J. Transition from a uni- to a bimodal interfacial charge distribution in [Formula: see text]/[Formula: see text] upon cooling. Sci Rep 2020; 10:18359. [PMID: 33110119 PMCID: PMC7591581 DOI: 10.1038/s41598-020-74364-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2020] [Accepted: 09/17/2020] [Indexed: 11/09/2022] Open
Abstract
We present a combined resonant soft X-ray reflectivity and electric transport study of [Formula: see text]/[Formula: see text] field effect devices. The depth profiles with atomic layer resolution that are obtained from the resonant reflectivity reveal a pronounced temperature dependence of the two-dimensional electron liquid at the [Formula: see text]/[Formula: see text] interface. At room temperature the corresponding electrons are located close to the interface, extending down to 4 unit cells into the [Formula: see text] substrate. Upon cooling, however, these interface electrons assume a bimodal depth distribution: They spread out deeper into the [Formula: see text] and split into two distinct parts, namely one close to the interface with a thickness of about 4 unit cells and another centered around 9 unit cells from the interface. The results are consistent with theoretical predictions based on oxygen vacancies at the surface of the [Formula: see text] film and support the notion of a complex interplay between structural and electronic degrees of freedom.
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Affiliation(s)
- M. Zwiebler
- Institut für Festkörper- und Materialphysik, Technische Universität Dresden, 01062 Dresden, Germany
| | - E. Di Gennaro
- Dipartimento di Fisica “E. Pancini”, Università di Napoli “Federico II”, Complesso Universitario di Monte S. Angelo, Via Cintia, 80126 Naples, Italy
- CNR-SPIN, Complesso Universitario di Monte S. Angelo, Via Cintia, 80126 Naples, Italy
| | - J. E. Hamann-Borrero
- Institut für Festkörper- und Materialphysik, Technische Universität Dresden, 01062 Dresden, Germany
| | - T. Ritschel
- Institut für Festkörper- und Materialphysik, Technische Universität Dresden, 01062 Dresden, Germany
| | - R. J. Green
- Stewart Blusson Quantum Matter Institute, University of British Columbia, Vancouver, V6T 1Z1 Canada
- Department of Physics and Engineering Physics, University of Saskatchewan, Saskatoon, S7N 5E2 Canada
| | - G. A. Sawatzky
- Stewart Blusson Quantum Matter Institute, University of British Columbia, Vancouver, V6T 1Z1 Canada
| | - E. Schierle
- Helmholtz-Zentrum Berlin, BESSY, Albert-Einstein-Str. 15, 12489 Berlin, Germany
| | - E. Weschke
- Helmholtz-Zentrum Berlin, BESSY, Albert-Einstein-Str. 15, 12489 Berlin, Germany
| | - A. Leo
- Dipartimento di Fisica “E. R. Caianiello”, Università degli Studi di Salerno, Fisciano, Italy
- CNR-SPIN, Campus di Fisciano-Salerno, Fisciano, Italy
| | - F. Miletto Granozio
- CNR-SPIN, Complesso Universitario di Monte S. Angelo, Via Cintia, 80126 Naples, Italy
| | - J. Geck
- Institut für Festkörper- und Materialphysik, Technische Universität Dresden, 01062 Dresden, Germany
- Würzburg-Dresden Cluster of Excellence ct.qmat, Technische Universität Dresden, 01062 Dresden, Germany
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21
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Observation of the polaronic character of excitons in a two-dimensional semiconducting magnet CrI 3. Nat Commun 2020; 11:4780. [PMID: 32963250 PMCID: PMC7508859 DOI: 10.1038/s41467-020-18627-x] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2020] [Accepted: 08/27/2020] [Indexed: 11/16/2022] Open
Abstract
Exciton dynamics can be strongly affected by lattice vibrations through electron-phonon coupling. This is rarely explored in two-dimensional magnetic semiconductors. Focusing on bilayer CrI3, we first show the presence of strong electron-phonon coupling through temperature-dependent photoluminescence and absorption spectroscopy. We then report the observation of periodic broad modes up to the 8th order in Raman spectra, attributed to the polaronic character of excitons. We establish that this polaronic character is dominated by the coupling between the charge-transfer exciton at 1.96 eV and a longitudinal optical phonon at 120.6 cm−1. We further show that the emergence of long-range magnetic order enhances the electron-phonon coupling strength by ~50% and that the transition from layered antiferromagnetic to ferromagnetic order tunes the spectral intensity of the periodic broad modes, suggesting a strong coupling among the lattice, charge and spin in two-dimensional CrI3. Our study opens opportunities for tailoring light-matter interactions in two-dimensional magnetic semiconductors. Exciton dynamics can be strongly affected by lattice vibrations through electron-phonon (e-ph) coupling. Here, the authors show the presence of strong e-ph coupling in bilayer CrI3 and observe a Raman feature with periodic broad modes up to the 8th order, attributed to the polaronic character of excitons.
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22
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Geondzhian A, Sambri A, De Luca GM, Di Capua R, Di Gennaro E, Betto D, Rossi M, Peng YY, Fumagalli R, Brookes NB, Braicovich L, Gilmore K, Ghiringhelli G, Salluzzo M. Large Polarons as Key Quasiparticles in SrTiO_{3} and SrTiO_{3}-Based Heterostructures. PHYSICAL REVIEW LETTERS 2020; 125:126401. [PMID: 33016714 DOI: 10.1103/physrevlett.125.126401] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/04/2020] [Revised: 07/26/2020] [Accepted: 08/14/2020] [Indexed: 06/11/2023]
Abstract
Despite its simple structure and low degree of electronic correlation, SrTiO_{3} (STO) features collective phenomena linked to charge transport and, ultimately, superconductivity, that are not yet fully explained. Thus, a better insight into the nature of the quasiparticles shaping the electronic and conduction properties of STO is needed. We studied the low-energy excitations of bulk STO and of the LaAlO_{3}/SrTiO_{3} two-dimensional electron gas (2DEG) by Ti L_{3} edge resonant inelastic x-ray scattering. In all samples, we find the hallmark of polarons in the form of intense dd+phonon excitations, and a decrease of the LO3-mode electron-phonon coupling when going from insulating to highly conducting STO single crystals and heterostructures. Both results are attributed to the dynamic screening of the large polaron self-induced polarization, showing that the low-temperature physics of STO and STO-based 2DEGs is dominated by large polaron quasiparticles.
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Affiliation(s)
- Andrey Geondzhian
- ESRF-The European Synchrotron, 71 Avenue des Martyrs, CS 40220, F-38043 Grenoble, France
| | - Alessia Sambri
- CNR-SPIN Complesso Monte-Santangelo via Cinthia, I-80126 Napoli, Italy
| | - Gabriella M De Luca
- CNR-SPIN Complesso Monte-Santangelo via Cinthia, I-80126 Napoli, Italy
- Dipartimento di Fisica "Ettore Pancini" Università di Napoli "Federico II", Complesso Monte-Santangelo via Cinthia, I-80126 Napoli, Italy
| | - Roberto Di Capua
- CNR-SPIN Complesso Monte-Santangelo via Cinthia, I-80126 Napoli, Italy
- Dipartimento di Fisica "Ettore Pancini" Università di Napoli "Federico II", Complesso Monte-Santangelo via Cinthia, I-80126 Napoli, Italy
| | - Emiliano Di Gennaro
- CNR-SPIN Complesso Monte-Santangelo via Cinthia, I-80126 Napoli, Italy
- Dipartimento di Fisica "Ettore Pancini" Università di Napoli "Federico II", Complesso Monte-Santangelo via Cinthia, I-80126 Napoli, Italy
| | - Davide Betto
- ESRF-The European Synchrotron, 71 Avenue des Martyrs, CS 40220, F-38043 Grenoble, France
| | - Matteo Rossi
- Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, I-20133 Milano, Italy
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA
| | - Ying Ying Peng
- Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, I-20133 Milano, Italy
- International Center for Quantum Materials,School of Physics, Peking University, Beijing 100871, China
| | - Roberto Fumagalli
- Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, I-20133 Milano, Italy
| | - Nicholas B Brookes
- ESRF-The European Synchrotron, 71 Avenue des Martyrs, CS 40220, F-38043 Grenoble, France
| | - Lucio Braicovich
- ESRF-The European Synchrotron, 71 Avenue des Martyrs, CS 40220, F-38043 Grenoble, France
- Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, I-20133 Milano, Italy
| | - Keith Gilmore
- ESRF-The European Synchrotron, 71 Avenue des Martyrs, CS 40220, F-38043 Grenoble, France
- Condensed Matter Physics and Materials Science Division, Brookhaven National Laboratory, Upton, New York 11973-5000, USA
| | - Giacomo Ghiringhelli
- Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, I-20133 Milano, Italy
- CNR-SPIN, Piazza Leonardo da Vinci 32, I-20133 Milano, Italy
| | - Marco Salluzzo
- CNR-SPIN Complesso Monte-Santangelo via Cinthia, I-80126 Napoli, Italy
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23
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Anh LD, Kaneta S, Tokunaga M, Seki M, Tabata H, Tanaka M, Ohya S. High-Mobility 2D Hole Gas at a SrTiO 3 Interface. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2020; 32:e1906003. [PMID: 32103572 DOI: 10.1002/adma.201906003] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/12/2019] [Revised: 02/02/2020] [Indexed: 06/10/2023]
Abstract
Strontium titanate (SrTiO3 or STO) is important for oxide-based electronics as it serves as a standard substrate for a wide range of high-temperature superconducting cuprates, colossal magnetoresistive manganites, and multiferroics. Moreover, in its heterostructures with different materials, STO exhibits a broad spectrum of important physics such as superconductivity, magnetism, the quantum Hall effect, giant thermoelectric effect, and colossal ionic conductivity, most of which emerge in a two-dimensional (2D) electron gas (2DEG) formed at an STO interface. However, little is known about its counterpart system, a 2D hole gas (2DHG) at the STO interface. Here, a simple way of realizing a 2DHG with an ultrahigh mobility of 24 000 cm2 V-1 s-1 is demonstrated using an interface between STO and a thin amorphous FeOy layer, made by depositing a sub-nanometer-thick Fe layer on an STO substrate at room temperature. This mobility is the highest among those reported for holes in oxides. The carrier type can be switched from p-type (2DHG) to n-type (2DEG) by controlling the Fe thickness. This unprecedented method of forming a 2DHG at an STO interface provides a pathway to unexplored hole-related physics in this system and enables extremely low-cost and high-speed oxide electronics.
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Affiliation(s)
- Le Duc Anh
- Department of Electrical Engineering and Information Systems, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan
- Institute of Engineering Innovation, Graduate School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan
| | - Shingo Kaneta
- Department of Electrical Engineering and Information Systems, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan
| | - Masashi Tokunaga
- Institute for Solid State Physics, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa-shi, Chiba, 277-8581, Japan
| | - Munetoshi Seki
- Department of Electrical Engineering and Information Systems, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan
- Center for Spintronics Research Network (CSRN), The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan
| | - Hitoshi Tabata
- Department of Electrical Engineering and Information Systems, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan
- Center for Spintronics Research Network (CSRN), The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan
| | - Masaaki Tanaka
- Department of Electrical Engineering and Information Systems, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan
- Center for Spintronics Research Network (CSRN), The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan
| | - Shinobu Ohya
- Department of Electrical Engineering and Information Systems, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan
- Institute of Engineering Innovation, Graduate School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan
- Center for Spintronics Research Network (CSRN), The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan
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24
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Trier F, Vaz DC, Bruneel P, Noël P, Fert A, Vila L, Attané JP, Barthélémy A, Gabay M, Jaffrès H, Bibes M. Electric-Field Control of Spin Current Generation and Detection in Ferromagnet-Free SrTiO 3-Based Nanodevices. NANO LETTERS 2020; 20:395-401. [PMID: 31859513 DOI: 10.1021/acs.nanolett.9b04079] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Spintronics entails the generation, transport, manipulation and detection of spin currents, usually in hybrid architectures comprising interfaces whose impact on performance is detrimental. In addition, how spins are generated and detected is generally material specific and determined by the electronic structure. Here, we demonstrate spin current generation, transport and electrical detection, all within a single non-magnetic material system: a SrTiO3 two-dimensional electron gas (2DEG) with Rashba spin-orbit coupling. We show that the spin current is generated from a charge current by the 2D spin Hall effect, transported through a channel and reconverted into a charge current by the inverse 2D spin Hall effect. Furthermore, by adjusting the Fermi energy with a gate voltage we tune the generated and detected spin polarization and relate it to the complex multiorbital band structure of the 2DEG. We discuss the leading mechanisms of the spin-charge interconversion processes and argue for the potential of quantum oxide materials for future all-electrical low-power spin-based logic.
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Affiliation(s)
- Felix Trier
- Unité Mixte de Physique , CNRS, Thales, Univ. Paris-Sud, Université Paris-Saclay , 91767 Palaiseau , France
| | - Diogo C Vaz
- Unité Mixte de Physique , CNRS, Thales, Univ. Paris-Sud, Université Paris-Saclay , 91767 Palaiseau , France
| | - Pierre Bruneel
- Laboratoire de Physique des Solides UMR 8502 , Université Paris-Sud, Université Paris-Saclay , 91405 Orsay , France
| | - Paul Noël
- Université Grenoble Alpes, CEA, CNRS, Spintec , 38000 Grenoble , France
| | - Albert Fert
- Unité Mixte de Physique , CNRS, Thales, Univ. Paris-Sud, Université Paris-Saclay , 91767 Palaiseau , France
| | - Laurent Vila
- Université Grenoble Alpes, CEA, CNRS, Spintec , 38000 Grenoble , France
| | | | - Agnès Barthélémy
- Unité Mixte de Physique , CNRS, Thales, Univ. Paris-Sud, Université Paris-Saclay , 91767 Palaiseau , France
| | - Marc Gabay
- Laboratoire de Physique des Solides UMR 8502 , Université Paris-Sud, Université Paris-Saclay , 91405 Orsay , France
| | - Henri Jaffrès
- Unité Mixte de Physique , CNRS, Thales, Univ. Paris-Sud, Université Paris-Saclay , 91767 Palaiseau , France
| | - Manuel Bibes
- Unité Mixte de Physique , CNRS, Thales, Univ. Paris-Sud, Université Paris-Saclay , 91767 Palaiseau , France
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25
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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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26
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Medjanik K, Babenkov SV, Chernov S, Vasilyev D, Schönhense B, Schlueter C, Gloskovskii A, Matveyev Y, Drube W, Elmers HJ, Schönhense G. Progress in HAXPES performance combining full-field k-imaging with time-of-flight recording. JOURNAL OF SYNCHROTRON RADIATION 2019; 26:1996-2012. [PMID: 31721745 PMCID: PMC6853377 DOI: 10.1107/s1600577519012773] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/11/2019] [Accepted: 09/13/2019] [Indexed: 05/27/2023]
Abstract
An alternative approach to hard-X-ray photoelectron spectroscopy (HAXPES) has been established. The instrumental key feature is an increase of the dimensionality of the recording scheme from 2D to 3D. A high-energy momentum microscope detects electrons with initial kinetic energies up to 8 keV with a k-resolution of 0.025 Å-1, equivalent to an angular resolution of 0.034°. A special objective lens with k-space acceptance up to 25 Å-1 allows for simultaneous full-field imaging of many Brillouin zones. Combined with time-of-flight (ToF) parallel energy recording this yields maximum parallelization. Thanks to the high brilliance (1013 hν s-1 in a spot of <20 µm diameter) of beamline P22 at PETRA III (Hamburg, Germany), the microscope set a benchmark in HAXPES recording speed, i.e. several million counts per second for core-level signals and one million for d-bands of transition metals. The concept of tomographic k-space mapping established using soft X-rays works equally well in the hard X-ray range. Sharp valence band k-patterns of Re, collected at an excitation energy of 6 keV, correspond to direct transitions to the 28th repeated Brillouin zone. Measured total energy resolutions (photon bandwidth plus ToF-resolution) are 62 meV and 180 meV FWHM at 5.977 keV for monochromator crystals Si(333) and Si(311) and 450 meV at 4.0 keV for Si(111). Hard X-ray photoelectron diffraction (hXPD) patterns with rich fine structure are recorded within minutes. The short photoelectron wavelength (10% of the interatomic distance) `amplifies' phase differences, making full-field hXPD a sensitive structural tool.
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Affiliation(s)
- K. Medjanik
- Institut für Physik, Johannes Gutenberg Universität Mainz, D-55099 Mainz, Germany
| | - S. V. Babenkov
- Institut für Physik, Johannes Gutenberg Universität Mainz, D-55099 Mainz, Germany
| | - S. Chernov
- Institut für Physik, Johannes Gutenberg Universität Mainz, D-55099 Mainz, Germany
| | - D. Vasilyev
- Institut für Physik, Johannes Gutenberg Universität Mainz, D-55099 Mainz, Germany
| | - B. Schönhense
- Department of Bioengineering, Imperial College London, UK
| | - C. Schlueter
- DESY Photon Science, Notkestrasse 85, 22607 Hamburg, Germany
| | - A. Gloskovskii
- DESY Photon Science, Notkestrasse 85, 22607 Hamburg, Germany
| | - Yu. Matveyev
- DESY Photon Science, Notkestrasse 85, 22607 Hamburg, Germany
| | - W. Drube
- DESY Photon Science, Notkestrasse 85, 22607 Hamburg, Germany
| | - H. J. Elmers
- Institut für Physik, Johannes Gutenberg Universität Mainz, D-55099 Mainz, Germany
| | - G. Schönhense
- Institut für Physik, Johannes Gutenberg Universität Mainz, D-55099 Mainz, Germany
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27
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Sio WH, Verdi C, Poncé S, Giustino F. Polarons from First Principles, without Supercells. PHYSICAL REVIEW LETTERS 2019; 122:246403. [PMID: 31322376 DOI: 10.1103/physrevlett.122.246403] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/09/2019] [Indexed: 06/10/2023]
Abstract
We develop a formalism and a computational method to study polarons in insulators and semiconductors from first principles. Unlike in standard calculations requiring large supercells, we solve a secular equation involving phonons and electron-phonon matrix elements from density-functional perturbation theory, in a spirit similar to the Bethe-Salpeter equation for excitons. We show that our approach describes seamlessly large and small polarons, and we illustrate its capability by calculating wave functions, formation energies, and spectral decomposition of polarons in LiF and Li_{2}O_{2}.
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Affiliation(s)
- Weng Hong Sio
- Department of Chemistry, Physical and Theoretical Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QZ, United Kingdom
- Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH, United Kingdom
| | - Carla Verdi
- Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH, United Kingdom
| | - Samuel Poncé
- Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH, United Kingdom
| | - Feliciano Giustino
- Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH, United Kingdom
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28
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Porer M, Fechner M, Bothschafter EM, Rettig L, Narayan A, Radovic M, Savoini M, Esposito V, Rittmann J, Kubli M, Kubacka T, Huber T, Neugebauer M, Abreu E, Grübel S, Beaud P, Ingold G, Lantz G, Parchenko S, Song S, Sato T, Aschauer U, Spaldin N, Johnson SL, Staub U. Optically induced transient enhancement of a structural order parameter. EPJ WEB OF CONFERENCES 2019. [DOI: 10.1051/epjconf/201920507001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We photoexcite SrTiO3 and EuTiO3 in their purely soft-mode-driven structurally distorted phase and trace the structural order parameter via ultra-short x-rays. We observe a rapid decay for SrTiO3 and an intriguing transient enhancement for EuTiO3.
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29
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Chikina A, Lechermann F, Husanu MA, Caputo M, Cancellieri C, Wang X, Schmitt T, Radovic M, Strocov VN. Orbital Ordering of the Mobile and Localized Electrons at Oxygen-Deficient LaAlO 3/SrTiO 3 Interfaces. ACS NANO 2018; 12:7927-7935. [PMID: 29995384 DOI: 10.1021/acsnano.8b02335] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Interfacing different transition-metal oxides opens a route to functionalizing their rich interplay of electron, spin, orbital, and lattice degrees of freedom for electronic and spintronic devices. Electronic and magnetic properties of SrTiO3-based interfaces hosting a mobile two-dimensional electron system (2DES) are strongly influenced by oxygen vacancies, which form an electronic dichotomy, where strongly correlated localized electrons in the in-gap states (IGSs) coexist with noncorrelated delocalized 2DES. Here, we use resonant soft-X-ray photoelectron spectroscopy to prove the eg character of the IGSs, as opposed to the t2g character of the 2DES in the paradigmatic LaAlO3/SrTiO3 interface. We furthermore separate the d xy and d xz/d xz orbital contributions based on deeper consideration of the resonant photoexcitation process in terms of orbital and momentum selectivity. Supported by a self-consistent combination of density functional theory and dynamical mean field theory calculations, this experiment identifies local orbital reconstruction that goes beyond the conventional eg- vs-t2g band ordering. A hallmark of oxygen-deficient LaAlO3/SrTiO3 is a significant hybridization of the eg and t2g orbitals. Our findings provide routes for tuning the electronic and magnetic properties of oxide interfaces through "defect engineering" with oxygen vacancies.
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Affiliation(s)
- Alla Chikina
- Swiss Light Source, Paul Scherrer Institute , Villigen CH-5232 , Switzerland
| | - Frank Lechermann
- Institut für Theoretische Physik , Universität Hamburg , Jungiusstrasse 9 , Hamburg DE-20355 , Germany
| | - Marius-Adrian Husanu
- Swiss Light Source, Paul Scherrer Institute , Villigen CH-5232 , Switzerland
- National Institute of Materials Physics , Atomistilor 405A , Magurele RO-077125 , Romania
| | - Marco Caputo
- Swiss Light Source, Paul Scherrer Institute , Villigen CH-5232 , Switzerland
| | - Claudia Cancellieri
- Swiss Light Source, Paul Scherrer Institute , Villigen CH-5232 , Switzerland
- Empa, Swiss Federal Laboratories for Materials Science & Technology , Ueberlandstrasse 129 , Duebendorf CH-8600 , Switzerland
| | - Xiaoqiang Wang
- Swiss Light Source, Paul Scherrer Institute , Villigen CH-5232 , Switzerland
| | - Thorsten Schmitt
- Swiss Light Source, Paul Scherrer Institute , Villigen CH-5232 , Switzerland
| | - Milan Radovic
- Swiss Light Source, Paul Scherrer Institute , Villigen CH-5232 , Switzerland
| | - Vladimir N Strocov
- Swiss Light Source, Paul Scherrer Institute , Villigen CH-5232 , Switzerland
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30
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Schlipf M, Poncé S, Giustino F. Carrier Lifetimes and Polaronic Mass Enhancement in the Hybrid Halide Perovskite CH_{3}NH_{3}PbI_{3} from Multiphonon Fröhlich Coupling. PHYSICAL REVIEW LETTERS 2018; 121:086402. [PMID: 30192620 DOI: 10.1103/physrevlett.121.086402] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/12/2018] [Indexed: 06/08/2023]
Abstract
We elucidate the nature of the electron-phonon interaction in the archetypal hybrid perovskite CH_{3}NH_{3}PbI_{3} using ab initio many-body calculations and an exactly solvable model. We demonstrate that electrons and holes near the band edges primarily interact with three distinct groups of longitudinal-optical vibrations, in order of importance: the stretching of the Pb-I bond, the bending of the Pb-I-Pb bonds, and the libration of the organic cations. These polar phonons induce ultrafast intraband carrier relaxation over timescales of 6-30 fs and yield polaron effective masses 28% heavier than the bare band masses. These findings allow us to rationalize previous experimental observations and provide a key to understanding carrier dynamics in halide perovskites.
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Affiliation(s)
- Martin Schlipf
- Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH, United Kingdom
| | - Samuel Poncé
- Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH, United Kingdom
| | - Feliciano Giustino
- Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH, United Kingdom
- Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14853, USA
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31
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Porer M, Fechner M, Bothschafter EM, Rettig L, Savoini M, Esposito V, Rittmann J, Kubli M, Neugebauer MJ, Abreu E, Kubacka T, Huber T, Lantz G, Parchenko S, Grübel S, Paarmann A, Noack J, Beaud P, Ingold G, Aschauer U, Johnson SL, Staub U. Ultrafast Relaxation Dynamics of the Antiferrodistortive Phase in Ca Doped SrTiO_{3}. PHYSICAL REVIEW LETTERS 2018; 121:055701. [PMID: 30118273 DOI: 10.1103/physrevlett.121.055701] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/30/2018] [Indexed: 06/08/2023]
Abstract
The ultrafast dynamics of the octahedral rotation in Ca:SrTiO_{3} is studied by time-resolved x-ray diffraction after photoexcitation over the band gap. By monitoring the diffraction intensity of a superlattice reflection that is directly related to the structural order parameter of the soft-mode driven antiferrodistortive phase in Ca:SrTiO_{3}, we observe an ultrafast relaxation on a 0.2 ps timescale of the rotation of the oxygen octahedron, which is found to be independent of the initial temperature despite large changes in the corresponding soft-mode frequency. A further, much smaller reduction on a slower picosecond timescale is attributed to thermal effects. Time-dependent density-functional-theory calculations show that the fast response can be ascribed to an ultrafast displacive modification of the soft-mode potential towards the normal state induced by holes created in the oxygen 2p states.
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Affiliation(s)
- M Porer
- Swiss Light Source, Paul Scherrer Institute, 5232 Villigen-PSI, Switzerland
| | - M Fechner
- Max Planck Institute for the Structure and Dynamics of Matter, CFEL, 22761 Hamburg, Germany
- Materials Theory, ETH Zürich, 8093 Zürich, Switzerland
| | - E M Bothschafter
- Swiss Light Source, Paul Scherrer Institute, 5232 Villigen-PSI, Switzerland
| | - L Rettig
- Swiss Light Source, Paul Scherrer Institute, 5232 Villigen-PSI, Switzerland
- Department of Physical Chemistry, Fritz Haber Institute of the Max Planck Society, 14195 Berlin, Germany
| | - M Savoini
- Swiss Light Source, Paul Scherrer Institute, 5232 Villigen-PSI, Switzerland
- Institute for Quantum Electronics, ETH Zürich, 8093 Zürich, Switzerland
| | - V Esposito
- Swiss Light Source, Paul Scherrer Institute, 5232 Villigen-PSI, Switzerland
| | - J Rittmann
- Swiss Light Source, Paul Scherrer Institute, 5232 Villigen-PSI, Switzerland
| | - M Kubli
- Institute for Quantum Electronics, ETH Zürich, 8093 Zürich, Switzerland
| | - M J Neugebauer
- Institute for Quantum Electronics, ETH Zürich, 8093 Zürich, Switzerland
| | - E Abreu
- Institute for Quantum Electronics, ETH Zürich, 8093 Zürich, Switzerland
| | - T Kubacka
- Institute for Quantum Electronics, ETH Zürich, 8093 Zürich, Switzerland
| | - T Huber
- Institute for Quantum Electronics, ETH Zürich, 8093 Zürich, Switzerland
| | - G Lantz
- Institute for Quantum Electronics, ETH Zürich, 8093 Zürich, Switzerland
| | - S Parchenko
- Swiss Light Source, Paul Scherrer Institute, 5232 Villigen-PSI, Switzerland
| | - S Grübel
- Swiss Light Source, Paul Scherrer Institute, 5232 Villigen-PSI, Switzerland
| | - A Paarmann
- Department of Physical Chemistry, Fritz Haber Institute of the Max Planck Society, 14195 Berlin, Germany
| | - J Noack
- Department of Inorganic Chemistry, Fritz Haber Institute of the Max Planck Society, 14195 Berlin, Germany
| | - P Beaud
- Swiss Light Source, Paul Scherrer Institute, 5232 Villigen-PSI, Switzerland
| | - G Ingold
- Swiss Light Source, Paul Scherrer Institute, 5232 Villigen-PSI, Switzerland
| | - U Aschauer
- Department of Chemistry and Biochemistry, University of Bern, 3012 Bern, Switzerland
| | - S L Johnson
- Institute for Quantum Electronics, ETH Zürich, 8093 Zürich, Switzerland
| | - U Staub
- Swiss Light Source, Paul Scherrer Institute, 5232 Villigen-PSI, Switzerland
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32
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Li D, Lemal S, Gariglio S, Wu Z, Fête A, Boselli M, Ghosez P, Triscone J. Probing Quantum Confinement and Electronic Structure at Polar Oxide Interfaces. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2018; 5:1800242. [PMID: 30128239 PMCID: PMC6097152 DOI: 10.1002/advs.201800242] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/12/2018] [Revised: 04/28/2018] [Indexed: 06/08/2023]
Abstract
Polar discontinuities occurring at interfaces between two materials constitute both a challenge and an opportunity in the study and application of a variety of devices. In order to cure the large electric field occurring in such structures, a reconfiguration of the charge landscape sets in at the interface via chemical modifications, adsorbates, or charge transfer. In the latter case, one may expect a local electronic doping of one material: one example is the two-dimensional electron liquid (2DEL) appearing in SrTiO3 once covered by a polar LaAlO3 layer. Here, it is shown that tuning the formal polarization of a (La,Al)1-x (Sr,Ti) x O3 (LASTO:x) overlayer modifies the quantum confinement of the 2DEL in SrTiO3 and its electronic band structure. The analysis of the behavior in magnetic field of superconducting field-effect devices reveals, in agreement with ab initio calculations and self-consistent Poisson-Schrödinger modeling, that quantum confinement and energy splitting between electronic bands of different symmetries strongly depend on the interface total charge densities. These results strongly support the polar discontinuity mechanisms with a full charge transfer to explain the origin of the 2DEL at the celebrated LaAlO3/SrTiO3 interface and demonstrate an effective tool for tailoring the electronic structure at oxide interfaces.
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Affiliation(s)
- Danfeng Li
- Department of Quantum Matter PhysicsUniversity of Geneva24 quai Ernest‐AnsermetCH‐1211Geneva 4Switzerland
| | - Sébastien Lemal
- Theoretical Materials PhysicsQ‐MATCESAMUniversité de LiègeB‐4000LiègeBelgium
| | - Stefano Gariglio
- Department of Quantum Matter PhysicsUniversity of Geneva24 quai Ernest‐AnsermetCH‐1211Geneva 4Switzerland
| | - Zhenping Wu
- Department of Quantum Matter PhysicsUniversity of Geneva24 quai Ernest‐AnsermetCH‐1211Geneva 4Switzerland
- State Key Laboratory of Information Photonics and Optical Communications and School of ScienceBeijing University of Posts and TelecommunicationsBeijing100876China
| | - Alexandre Fête
- Department of Quantum Matter PhysicsUniversity of Geneva24 quai Ernest‐AnsermetCH‐1211Geneva 4Switzerland
| | - Margherita Boselli
- Department of Quantum Matter PhysicsUniversity of Geneva24 quai Ernest‐AnsermetCH‐1211Geneva 4Switzerland
| | - Philippe Ghosez
- Theoretical Materials PhysicsQ‐MATCESAMUniversité de LiègeB‐4000LiègeBelgium
| | - Jean‐Marc Triscone
- Department of Quantum Matter PhysicsUniversity of Geneva24 quai Ernest‐AnsermetCH‐1211Geneva 4Switzerland
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k-space imaging of anisotropic 2D electron gas in GaN/GaAlN high-electron-mobility transistor heterostructures. Nat Commun 2018; 9:2653. [PMID: 29992961 PMCID: PMC6041315 DOI: 10.1038/s41467-018-04354-x] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2017] [Accepted: 04/09/2018] [Indexed: 11/29/2022] Open
Abstract
Nanostructures based on buried interfaces and heterostructures are at the heart of modern semiconductor electronics as well as future devices utilizing spintronics, multiferroics, topological effects, and other novel operational principles. Knowledge of electronic structure of these systems resolved in electron momentum k delivers unprecedented insights into their physics. Here we explore 2D electron gas formed in GaN/AlGaN high-electron-mobility transistor heterostructures with an ultrathin barrier layer, key elements in current high-frequency and high-power electronics. Its electronic structure is accessed with angle-resolved photoelectron spectroscopy whose probing depth is pushed to a few nanometers using soft-X-ray synchrotron radiation. The experiment yields direct k-space images of the electronic structure fundamentals of this system—the Fermi surface, band dispersions and occupancy, and the Fourier composition of wavefunctions encoded in the k-dependent photoemission intensity. We discover significant planar anisotropy of the electron Fermi surface and effective mass connected with relaxation of the interfacial atomic positions, which translates into nonlinear (high-field) transport properties of the GaN/AlGaN heterostructures as an anisotropy of the saturation drift velocity of the 2D electrons. Semiconductor heterostructures hosting two-dimensional electron gases are widely used today in high-electron-mobility transistors. Here, the authors probe the electronic structure in GaN/AlGaN, heterostructures, discovering planar anisotropy of the electron Fermi surface, offering new insights into transport properties.
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Riley JM, Caruso F, Verdi C, Duffy LB, Watson MD, Bawden L, Volckaert K, van der Laan G, Hesjedal T, Hoesch M, Giustino F, King PDC. Crossover from lattice to plasmonic polarons of a spin-polarised electron gas in ferromagnetic EuO. Nat Commun 2018; 9:2305. [PMID: 29899336 PMCID: PMC5998015 DOI: 10.1038/s41467-018-04749-w] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2018] [Accepted: 05/22/2018] [Indexed: 11/10/2022] Open
Abstract
Strong many-body interactions in solids yield a host of fascinating and potentially useful physical properties. Here, from angle-resolved photoemission experiments and ab initio many-body calculations, we demonstrate how a strong coupling of conduction electrons with collective plasmon excitations of their own Fermi sea leads to the formation of plasmonic polarons in the doped ferromagnetic semiconductor EuO. We observe how these exhibit a significant tunability with charge carrier doping, leading to a polaronic liquid that is qualitatively distinct from its more conventional lattice-dominated analogue. Our study thus suggests powerful opportunities for tailoring quantum many-body interactions in solids via dilute charge carrier doping.
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Affiliation(s)
- J M Riley
- SUPA, School of Physics and Astronomy, University of St. Andrews, St. Andrews, KY16 9SS, UK
- Diamond Light Source, Harwell Campus, Didcot, OX11 0DE, UK
| | - F Caruso
- Department of Materials, University of Oxford, Parks Road, Oxford, OX1 3PH, UK
- Institut für Physik and IRIS Adlershof, Humboldt-Universität zu Berlin, Berlin, 12489, Germany
| | - C Verdi
- Department of Materials, University of Oxford, Parks Road, Oxford, OX1 3PH, UK
| | - L B Duffy
- Department of Physics, University of Oxford, Oxford, OX1 3PU, UK
- ISIS, STFC, Rutherford Appleton Laboratory, Didcot, OX11 0QX, UK
| | - M D Watson
- SUPA, School of Physics and Astronomy, University of St. Andrews, St. Andrews, KY16 9SS, UK
- Diamond Light Source, Harwell Campus, Didcot, OX11 0DE, UK
| | - L Bawden
- SUPA, School of Physics and Astronomy, University of St. Andrews, St. Andrews, KY16 9SS, UK
| | - K Volckaert
- SUPA, School of Physics and Astronomy, University of St. Andrews, St. Andrews, KY16 9SS, UK
| | - G van der Laan
- Diamond Light Source, Harwell Campus, Didcot, OX11 0DE, UK
| | - T Hesjedal
- Department of Physics, University of Oxford, Oxford, OX1 3PU, UK
| | - M Hoesch
- Diamond Light Source, Harwell Campus, Didcot, OX11 0DE, UK.
- DESY Photon Science, Deutsches Elektronen-Synchrotron, Hamburg, D-22603, Germany.
| | - F Giustino
- Department of Materials, University of Oxford, Parks Road, Oxford, OX1 3PH, UK.
- Department of Materials Science and Engineering, Cornell University, Ithaca, New York, 14853, USA.
| | - P D C King
- SUPA, School of Physics and Astronomy, University of St. Andrews, St. Andrews, KY16 9SS, UK.
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35
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Kormondy KJ, Gao L, Li X, Lu S, Posadas AB, Shen S, Tsoi M, McCartney MR, Smith DJ, Zhou J, Lev LL, Husanu MA, Strocov VN, Demkov AA. Large positive linear magnetoresistance in the two-dimensional t 2g electron gas at the EuO/SrTiO 3 interface. Sci Rep 2018; 8:7721. [PMID: 29769572 PMCID: PMC5955958 DOI: 10.1038/s41598-018-26017-z] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2017] [Accepted: 05/03/2018] [Indexed: 11/09/2022] Open
Abstract
The development of novel nano-oxide spintronic devices would benefit greatly from interfacing with emergent phenomena at oxide interfaces. In this paper, we integrate highly spin-split ferromagnetic semiconductor EuO onto perovskite SrTiO3 (001). A careful deposition of Eu metal by molecular beam epitaxy results in EuO growth via oxygen out-diffusion from SrTiO3. This in turn leaves behind a highly conductive interfacial layer through generation of oxygen vacancies. Below the Curie temperature of 70 K of EuO, this spin-polarized two-dimensional t 2g electron gas at the EuO/SrTiO3 interface displays very large positive linear magnetoresistance (MR). Soft x-ray angle-resolved photoemission spectroscopy (SX-ARPES) reveals the t 2g nature of the carriers. First principles calculations strongly suggest that Zeeman splitting, caused by proximity magnetism and oxygen vacancies in SrTiO3, is responsible for the MR. This system offers an as-yet-unexplored route to pursue proximity-induced effects in the oxide two-dimensional t 2g electron gas.
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Affiliation(s)
- Kristy J Kormondy
- Department of Physics, The University of Texas at Austin, Austin, Texas, 78712, USA
| | - Lingyuan Gao
- Department of Physics, The University of Texas at Austin, Austin, Texas, 78712, USA
| | - Xiang Li
- Materials Science and Engineering Program/Mechanical Engineering, University of Texas at Austin, Austin, Texas, 78712, USA
| | - Sirong Lu
- School of Engineering for Matter, Transport and Energy, Arizona State University, Tempe, AZ, 85287, USA
| | - Agham B Posadas
- Department of Physics, The University of Texas at Austin, Austin, Texas, 78712, USA
| | - Shida Shen
- Department of Physics, The University of Texas at Austin, Austin, Texas, 78712, USA
| | - Maxim Tsoi
- Department of Physics, The University of Texas at Austin, Austin, Texas, 78712, USA
| | - Martha R McCartney
- Department of Physics, Arizona State University, Tempe, Arizona, 85287, USA
| | - David J Smith
- Department of Physics, Arizona State University, Tempe, Arizona, 85287, USA
| | - Jianshi Zhou
- Materials Science and Engineering Program/Mechanical Engineering, University of Texas at Austin, Austin, Texas, 78712, USA
| | - Leonid L Lev
- Paul Scherrer Institute, Swiss Light Source, CH-5232, Villigen PSI, Switzerland.,National Research Centre "Kurchatov Institute", 1 Akademika Kurchatova pl., 123182, Moscow, Russia
| | - Marius-Adrian Husanu
- Paul Scherrer Institute, Swiss Light Source, CH-5232, Villigen PSI, Switzerland.,National Institute of Materials Physics, 405A Atomistilor Str., 077125, Magurele, Romania
| | - Vladimir N Strocov
- Paul Scherrer Institute, Swiss Light Source, CH-5232, Villigen PSI, Switzerland
| | - Alexander A Demkov
- Department of Physics, The University of Texas at Austin, Austin, Texas, 78712, USA.
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Abstract
The effect of electron-phonon coupling in materials can be interpreted as a dressing of the electronic structure by the lattice vibration, leading to vibrational replicas and hybridization of electronic states. In solids, a resonantly excited coherent phonon leads to a periodic oscillation of the atomic lattice in a crystal structure bringing the material into a nonequilibrium electronic configuration. Periodically oscillating quantum systems can be understood in terms of Floquet theory, which has a long tradition in the study of semiclassical light-matter interaction. Here, we show that the concepts of Floquet analysis can be applied to coherent lattice vibrations. This coupling leads to phonon-dressed quasi-particles imprinting specific signatures in the spectrum of the electronic structure. Such dressed electronic states can be detected by time- and angular-resolved photoelectron spectroscopy (ARPES) manifesting as sidebands to the equilibrium band structure. Taking graphene as a paradigmatic material with strong electron-phonon interaction and nontrivial topology, we show how the phonon-dressed states display an intricate sideband structure revealing the electron-phonon coupling at the Brillouin zone center and topological ordering of the Dirac bands. We demonstrate that if time-reversal symmetry is broken by the coherent lattice perturbations a topological phase transition can be induced. This work establishes that the recently demonstrated concept of light-induced nonequilibrium Floquet phases can also be applied when using coherent phonon modes for the dynamical control of material properties.
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Affiliation(s)
- Hannes Hübener
- Max Planck Institute for the Structure and Dynamics of Matter , Luruper Chaussee 149, 22761 Hamburg, Germany
- Center for Free-Electron Laser Science and Department of Physics, University of Hamburg , Luruper Chaussee 149, 22761 Hamburg, Germany
| | - Umberto De Giovannini
- Max Planck Institute for the Structure and Dynamics of Matter , Luruper Chaussee 149, 22761 Hamburg, Germany
- Center for Free-Electron Laser Science and Department of Physics, University of Hamburg , Luruper Chaussee 149, 22761 Hamburg, Germany
| | - Angel Rubio
- Max Planck Institute for the Structure and Dynamics of Matter , Luruper Chaussee 149, 22761 Hamburg, Germany
- Center for Free-Electron Laser Science and Department of Physics, University of Hamburg , Luruper Chaussee 149, 22761 Hamburg, Germany
- Center for Computational Quantum Physics (CCQ), The Flatiron Institute , 162 Fifth Avenue, New York, New York 22761, USA
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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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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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Mattoni G, Baek DJ, Manca N, Verhagen N, Groenendijk DJ, Kourkoutis LF, Filippetti A, Caviglia AD. Insulator-to-Metal Transition at Oxide Interfaces Induced by WO 3 Overlayers. ACS APPLIED MATERIALS & INTERFACES 2017; 9:42336-42343. [PMID: 29111647 DOI: 10.1021/acsami.7b13202] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Interfaces between complex oxides constitute a unique playground for two-dimensional electron systems (2DESs), where superconductivity and magnetism can arise from combinations of bulk insulators. The 2DES at the LaAlO3/SrTiO3 interface is one of the most studied in this regard, and its origin is determined by the polar field in LaAlO3 as well as by the presence of point defects, like oxygen vacancies and intermixed cations. These defects usually reside in the conduction channel and are responsible for a decrease of the electronic mobility. In this work, we use an amorphous WO3 overlayer to obtain a high-mobility 2DES in WO3/LaAlO3/SrTiO3 heterostructures. The studied system shows a sharp insulator-to-metal transition as a function of both LaAlO3 and WO3 layer thickness. Low-temperature magnetotransport reveals a strong magnetoresistance reaching 900% at 10 T and 1.5 K, the presence of multiple conduction channels with carrier mobility up to 80 000 cm2 V-1 s-1, and quantum oscillations of conductance.
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Affiliation(s)
- Giordano Mattoni
- Kavli Institute of Nanoscience, Delft University of Technology , 2628 CJ Delft, The Netherlands
| | | | - Nicola Manca
- Kavli Institute of Nanoscience, Delft University of Technology , 2628 CJ Delft, The Netherlands
| | - Nils Verhagen
- Kavli Institute of Nanoscience, Delft University of Technology , 2628 CJ Delft, The Netherlands
| | - Dirk J Groenendijk
- Kavli Institute of Nanoscience, Delft University of Technology , 2628 CJ Delft, The Netherlands
| | | | - Alessio Filippetti
- Dipartimento di Fisica, Università di Cagliari , Cagliari, Monserrato 09042-I, Italy
- CNR-IOM, Istituto Officina dei Materiali, Cittadella Universitaria , Cagliari, Monserrato 09042-I, Italy
| | - Andrea D Caviglia
- Kavli Institute of Nanoscience, Delft University of Technology , 2628 CJ Delft, The Netherlands
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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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41
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Dai W, Yang M, Lee H, Lee JW, Eom CB, Cen C. Tailoring the Doping Mechanisms at Oxide Interfaces in Nanoscale. NANO LETTERS 2017; 17:5620-5625. [PMID: 28806520 DOI: 10.1021/acs.nanolett.7b02508] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Here, we demonstrate the nanoscale manipulations of two types of charge transfer to the LaAlO3/SrTiO3 interfaces: one from surface adsorbates and another from oxygen vacancies inside LaAlO3 films. This method can be used to produce multiple insulating and metallic interface states with distinct carrier properties that are highly stable in air. By reconfiguring the patterning and comparing interface structures formed from different doping sources, effects of extrinsic and intrinsic material characters on the transport properties can be distinguished. In particular, a multisubband to single-subband transition controlled by the structural phases in SrTiO3 was revealed. In addition, the transient behaviors of nanostructures also provided a unique opportunity to study the nanoscale diffusions of adsorbates and oxygen vacancies in oxide heterostructures. Knowledge of such dynamic processes is important for nanodevice implementations.
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Affiliation(s)
- Weitao Dai
- Department of Physics and Astronomy, West Virginia University , Morgantown, West Virginia 26506, United States
| | - Ming Yang
- Department of Physics and Astronomy, West Virginia University , Morgantown, West Virginia 26506, United States
| | - Hyungwoo Lee
- Department of Material Science and Engineering, University of Wisconsin-Madison , Madison, Wisconsin 53706, United States
| | - Jung-Woo Lee
- Department of Material Science and Engineering, University of Wisconsin-Madison , Madison, Wisconsin 53706, United States
| | - Chang-Beom Eom
- Department of Material Science and Engineering, University of Wisconsin-Madison , Madison, Wisconsin 53706, United States
| | - Cheng Cen
- Department of Physics and Astronomy, West Virginia University , Morgantown, West Virginia 26506, United States
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42
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Verdi C, Caruso F, Giustino F. Origin of the crossover from polarons to Fermi liquids in transition metal oxides. Nat Commun 2017; 8:15769. [PMID: 28593950 PMCID: PMC5472750 DOI: 10.1038/ncomms15769] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2016] [Accepted: 04/24/2017] [Indexed: 11/28/2022] Open
Abstract
Transition metal oxides host a wealth of exotic phenomena ranging from charge, orbital and magnetic order to nontrivial topological phases and superconductivity. In order to translate these unique materials properties into device functionalities these materials must be doped; however, the nature of carriers and their conduction mechanism at the atomic scale remain unclear. Recent angle-resolved photoelectron spectroscopy investigations provided insight into these questions, revealing that the carriers of prototypical metal oxides undergo a transition from a polaronic liquid to a Fermi liquid regime with increasing doping. Here, by performing ab initio many-body calculations of angle-resolved photoemission spectra of titanium dioxide, we show that this transition originates from non-adiabatic polar electron-phonon coupling, and occurs when the frequency of plasma oscillations exceeds that of longitudinal-optical phonons. This finding suggests that a universal mechanism may underlie polaron formation in transition metal oxides, and provides a pathway for engineering emergent properties in quantum matter.
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Affiliation(s)
- Carla Verdi
- Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH, UK
| | - Fabio Caruso
- Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH, UK
| | - Feliciano Giustino
- Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH, UK
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Stucky A, Scheerer GW, Ren Z, Jaccard D, Poumirol JM, Barreteau C, Giannini E, van der Marel D. Isotope effect in superconducting n-doped SrTiO 3. Sci Rep 2016; 6:37582. [PMID: 27892485 PMCID: PMC5124855 DOI: 10.1038/srep37582] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2016] [Accepted: 10/31/2016] [Indexed: 11/20/2022] Open
Abstract
We report the influence on the superconducting critical temperature Tc in doped SrTiO3 of the substitution of the natural 16O atoms by the heavier isotope 18O. We observe that for a wide range of doping this substitution causes a strong (~50%) enhancement of Tc. Also the magnetic critical field Hc2 is increased by a factor ~2. Such a strong impact on Tc and Hc2, with a sign opposite to conventional superconductors, is unprecedented. The observed effect could be the consequence of strong coupling of the doped electrons to lattice vibrations (phonons), a notion which finds support in numerous optical and photo-emission studies. The unusually large size of the observed isotope effect supports a recent model for superconductivity in these materials based on strong coupling to the ferroelectric soft modes of SrTiO3.
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Affiliation(s)
- A. Stucky
- Department of Quantum Matter Physics, Université de Genève, CH-1211 Genève 4, Switzerland
| | - G. W. Scheerer
- Department of Quantum Matter Physics, Université de Genève, CH-1211 Genève 4, Switzerland
| | - Z. Ren
- Department of Quantum Matter Physics, Université de Genève, CH-1211 Genève 4, Switzerland
| | - D. Jaccard
- Department of Quantum Matter Physics, Université de Genève, CH-1211 Genève 4, Switzerland
| | - J.-M. Poumirol
- Department of Quantum Matter Physics, Université de Genève, CH-1211 Genève 4, Switzerland
| | - C. Barreteau
- Department of Quantum Matter Physics, Université de Genève, CH-1211 Genève 4, Switzerland
| | - E. Giannini
- Department of Quantum Matter Physics, Université de Genève, CH-1211 Genève 4, Switzerland
| | - D. van der Marel
- Department of Quantum Matter Physics, Université de Genève, CH-1211 Genève 4, Switzerland
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Bouravleuv AD, Lev LL, Piamonteze C, Wang X, Schmitt T, Khrebtov AI, Samsonenko YB, Kanski J, Cirlin GE, Strocov VN. Electronic structure of (In,Mn)As quantum dots buried in GaAs investigated by soft-x-ray ARPES. NANOTECHNOLOGY 2016; 27:425706. [PMID: 27631689 DOI: 10.1088/0957-4484/27/42/425706] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Electronic structure of a molecular beam epitaxy-grown system of (In,Mn)As quantum dots (QDs) buried in GaAs is explored with soft-x-ray angle-resolved photoelectron spectroscopy (ARPES) using photon energies around 1 keV. This technique, ideally suited for buried systems, extends the momentum-resolving capabilities of conventional ARPES with enhanced probing depth as well as elemental and chemical state specificity achieved with resonant photoexcitation. The experimental results resolve the dispersive energy bands of the GaAs substrate buried in ∼2 nm below the surface, and the impurity states (ISs) derived from the substitutional Mn atoms in the (In,Mn)As QDs and oxidized Mn atoms distributed near the surface. An energy shift of the Mn ISs in the QDs compared to (In,Mn)As DMS is attributed to the band offset and proximity effect at the interface with the surrounding GaAs. The absence of any ISs in the vicinity of the VBM relates the electron transport in (In,Mn)As QDs to the prototype (In,Mn)As diluted magnetic semiconductor. The SX-ARPES results are supported by measurements of the shallow core levels under variation of probing depth through photon energy. X-ray absorption measurements identify significant diffusion of interstitial Mn atoms out of the QDs towards the surface, and the role of magnetic circular dichroism is to block the ferromagnetic response of the (In,Mn)As QDs. Possible routes are drawn to tune the growth procedure aiming at practical applications of the (In,Mn)As based systems.
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Affiliation(s)
- A D Bouravleuv
- St.Petersburg Academic University RAS, 8-3 Khlopina st., 194021 St.Petersburg, Russia. Ioffe Physical Technical Institute RAS, 26 Politekhnicheskaya st., 194021 St.Petersburg, Russia. Institute for Analytical Instrumentation RAS, 31-33 Ivana Chernykh st., 190103 St.Petersburg, Russia. St.Petersburg State University, 7-9 Universitetskaya nab., 199034 St.Petersburg, Russia
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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: 18] [Impact Index Per Article: 2.3] [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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46
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Wang Z, McKeown Walker S, Tamai A, Wang Y, Ristic Z, Bruno FY, de la Torre A, Riccò S, Plumb NC, Shi M, Hlawenka P, Sánchez-Barriga J, Varykhalov A, Kim TK, Hoesch M, King PDC, Meevasana W, Diebold U, Mesot J, Moritz B, Devereaux TP, Radovic M, Baumberger F. Tailoring the nature and strength of electron-phonon interactions in the SrTiO3(001) 2D electron liquid. NATURE MATERIALS 2016; 15:835-839. [PMID: 27064529 DOI: 10.1038/nmat4623] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/25/2015] [Accepted: 03/10/2016] [Indexed: 06/05/2023]
Abstract
Surfaces and interfaces offer new possibilities for tailoring the many-body interactions that dominate the electrical and thermal properties of transition metal oxides. Here, we use the prototypical two-dimensional electron liquid (2DEL) at the SrTiO3(001) surface to reveal a remarkably complex evolution of electron-phonon coupling with the tunable carrier density of this system. At low density, where superconductivity is found in the analogous 2DEL at the LaAlO3/SrTiO3 interface, our angle-resolved photoemission data show replica bands separated by 100 meV from the main bands. This is a hallmark of a coherent polaronic liquid and implies long-range coupling to a single longitudinal optical phonon branch. In the overdoped regime the preferential coupling to this branch decreases and the 2DEL undergoes a crossover to a more conventional metallic state with weaker short-range electron-phonon interaction. These results place constraints on the theoretical description of superconductivity and allow a unified understanding of the transport properties in SrTiO3-based 2DELs.
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Affiliation(s)
- Z Wang
- Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
- Department of Quantum Matter Physics, University of Geneva, 24 Quai Ernest-Ansermet, 1211 Geneva 4, Switzerland
| | - S McKeown Walker
- Department of Quantum Matter Physics, University of Geneva, 24 Quai Ernest-Ansermet, 1211 Geneva 4, Switzerland
| | - A Tamai
- Department of Quantum Matter Physics, University of Geneva, 24 Quai Ernest-Ansermet, 1211 Geneva 4, Switzerland
| | - Y Wang
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
- Department of Applied Physics, Stanford University, Stanford, California 94305, USA
| | - Z Ristic
- Institute of Condensed Matter Physics, École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - F Y Bruno
- Department of Quantum Matter Physics, University of Geneva, 24 Quai Ernest-Ansermet, 1211 Geneva 4, Switzerland
| | - A de la Torre
- Department of Quantum Matter Physics, University of Geneva, 24 Quai Ernest-Ansermet, 1211 Geneva 4, Switzerland
| | - S Riccò
- Department of Quantum Matter Physics, University of Geneva, 24 Quai Ernest-Ansermet, 1211 Geneva 4, Switzerland
| | - N C Plumb
- Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
| | - M Shi
- Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
| | - P Hlawenka
- Helmholtz-Zentrum Berlin für Materialien und Energie, Elektronenspeicherring BESSY-II, 12489 Berlin, Germany
| | - J Sánchez-Barriga
- Helmholtz-Zentrum Berlin für Materialien und Energie, Elektronenspeicherring BESSY-II, 12489 Berlin, Germany
| | - A Varykhalov
- Helmholtz-Zentrum Berlin für Materialien und Energie, Elektronenspeicherring BESSY-II, 12489 Berlin, Germany
| | - T K Kim
- Diamond Light Source, Harwell Campus, Didcot OX11 0DE, UK
| | - M Hoesch
- Diamond Light Source, Harwell Campus, Didcot OX11 0DE, UK
| | - P D C King
- SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews, Fife KY16 9SS, UK
| | - W Meevasana
- School of Physics and NANOTEC-SUT Center of Excellence on Advanced Functional Nanomaterials, Suranaree University of Technology, Nakhon Ratchasima 30000, Thailand
| | - U Diebold
- Institute of Applied Physics, Vienna University of Technology, Wiedner Hauptstrasse 8-10/134, A-1040 Vienna, Austria
| | - J Mesot
- Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
- Institute of Condensed Matter Physics, École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
- Laboratory for Solid State Physics, ETH Zürich, CH-8093 Zürich, Switzerland
| | - B Moritz
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
| | - T P Devereaux
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
- Geballe Laboratory for Advanced Materials, Stanford University, Stanford, California 94305, USA
| | - M Radovic
- Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
- SwissFEL, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
| | - F Baumberger
- Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
- Department of Quantum Matter Physics, University of Geneva, 24 Quai Ernest-Ansermet, 1211 Geneva 4, Switzerland
- SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews, Fife KY16 9SS, UK
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Abstract
The thermoelectric properties of the (001) n-type 6.5STO/1.5LAO interface were investigated by means of the all-electron full-potential method based on the semi-classical Boltzmann theory.
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Affiliation(s)
- A. H. Reshak
- New Technologies – Research Centre
- University of West Bohemia
- 306 14 Pilsen
- Czech Republic
- School of Material Engineering
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