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Qiao L, Barone P, Yang B, King PDC, Ren W, Picozzi S. Electron doping as a handle to increase the Curie temperature in ferrimagnetic Mn 3Si 2X 6 (X = Se, Te). Phys Chem Chem Phys 2024; 26:8604-8612. [PMID: 38319643 DOI: 10.1039/d3cp05525f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2024]
Abstract
By analysing the results of ab initio simulations performed for Mn3Si2X6 (X = Se, Te), we first discuss the analogies and the differences in electronic and magnetic properties arising from the anion substitution, in terms of size, electronegativity, band widths of p electrons and spin-orbit coupling strengths. For example, through mean-field theory and simulations based on density functional theory, we demonstrate that magnetic frustration, known to be present in Mn3Si2Te6, also exists in Mn3Si2Se6 and leading to a ferrimagnetic ground state. Building on these results, we propose a strategy, electronic doping, to reduce the frustration and thus to increase the Curie temperature (TC). To this end, we first study the effect of electronic doping on the electronic structure and magnetic properties and discuss the differences in the two compounds, along with their causes. Secondly, we perform Monte-Carlo simulations, considering from the first to the fifth nearest-neighbor magnetic interactions and single-ion anisotropy, and show that electron doping efficiently raises the TC.
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Affiliation(s)
- Lei Qiao
- Physics Department, International Center of Quantum and Molecular Structures, Materials Genome Institute, State Key Laboratory of Advanced Special Steel, Shanghai Key Laboratory of High Temperature Superconductors, Shanghai University, Shanghai 200444, China.
- Consiglio Nazionale delle Ricerche (CNR-SPIN), Unità di Ricerca presso Terzi c/o Università "G. D'Annunzio", 66100 Chieti, Italy.
| | - Paolo Barone
- Consiglio Nazionale delle Ricerche (CNR-SPIN), Area della Ricerca di Tor Vergata, Via del Fosso del Cavaliere 100, I-00133 Rome, Italy
| | - Baishun Yang
- Consiglio Nazionale delle Ricerche (CNR-SPIN), Unità di Ricerca presso Terzi c/o Università "G. D'Annunzio", 66100 Chieti, Italy.
| | - Phil D C King
- SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews KY16 9SS, UK
| | - Wei Ren
- Physics Department, International Center of Quantum and Molecular Structures, Materials Genome Institute, State Key Laboratory of Advanced Special Steel, Shanghai Key Laboratory of High Temperature Superconductors, Shanghai University, Shanghai 200444, China.
| | - Silvia Picozzi
- Consiglio Nazionale delle Ricerche (CNR-SPIN), Unità di Ricerca presso Terzi c/o Università "G. D'Annunzio", 66100 Chieti, Italy.
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2
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Hilton J, Nanao Y, Flokstra M, Askari M, Smith TK, Di Falco A, King PDC, Wahl P, Adamson CS. The role of ion dissolution in metal and metal oxide surface inactivation of SARS-CoV-2. Appl Environ Microbiol 2024; 90:e0155323. [PMID: 38259079 PMCID: PMC10880620 DOI: 10.1128/aem.01553-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2023] [Accepted: 11/28/2023] [Indexed: 01/24/2024] Open
Abstract
Anti-viral surface coatings are under development to prevent viral fomite transmission from high-traffic touch surfaces in public spaces. Copper's anti-viral properties have been widely documented, but the anti-viral mechanism of copper surfaces is not fully understood. We screened a series of metal and metal oxide surfaces for anti-viral activity against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative agent of coronavirus disease (COVID-19). Copper and copper oxide surfaces exhibited superior anti-SARS-CoV-2 activity; however, the level of anti-viral activity was dependent on the composition of the carrier solution used to deliver virus inoculum. We demonstrate that copper ions released into solution from test surfaces can mediate virus inactivation, indicating a copper ion dissolution-dependent anti-viral mechanism. The level of anti-viral activity is, however, not dependent on the amount of copper ions released into solution per se. Instead, our findings suggest that degree of virus inactivation is dependent on copper ion complexation with other biomolecules (e.g., proteins/metabolites) in the virus carrier solution that compete with viral components. Although using tissue culture-derived virus inoculum is experimentally convenient to evaluate the anti-viral activity of copper-derived test surfaces, we propose that the high organic content of tissue culture medium reduces the availability of "uncomplexed" copper ions to interact with the virus, negatively affecting virus inactivation and hence surface anti-viral performance. We propose that laboratory anti-viral surface testing should include virus delivered in a physiologically relevant carrier solution (saliva or nasal secretions when testing respiratory viruses) to accurately predict real-life surface anti-viral performance when deployed in public spaces.IMPORTANCEThe purpose of evaluating the anti-viral activity of test surfaces in the laboratory is to identify surfaces that will perform efficiently in preventing fomite transmission when deployed on high-traffic touch surfaces in public spaces. The conventional method in laboratory testing is to use tissue culture-derived virus inoculum; however, this study demonstrates that anti-viral performance of test copper-containing surfaces is dependent on the composition of the carrier solution in which the virus inoculum is delivered to test surfaces. Therefore, we recommend that laboratory surface testing should include virus delivered in a physiologically relevant carrier solution to accurately predict real-life test surface performance in public spaces. Understanding the mechanism of virus inactivation is key to future rational design of improved anti-viral surfaces. Here, we demonstrate that release of copper ions from copper surfaces into small liquid droplets containing SARS-CoV-2 is a mechanism by which the virus that causes COVID-19 can be inactivated.
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Affiliation(s)
- Jane Hilton
- Biomedical Sciences Research Complex, School of Biology, University of St Andrews, St Andrews, Fife, United Kingdom
| | - Yoshiko Nanao
- SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews, Fife, United Kingdom
| | - Machiel Flokstra
- SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews, Fife, United Kingdom
| | - Meisam Askari
- SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews, Fife, United Kingdom
| | - Terry K. Smith
- Biomedical Sciences Research Complex, School of Biology, University of St Andrews, St Andrews, Fife, United Kingdom
| | - Andrea Di Falco
- SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews, Fife, United Kingdom
| | - Phil D. C. King
- SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews, Fife, United Kingdom
| | - Peter Wahl
- SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews, Fife, United Kingdom
| | - Catherine S. Adamson
- Biomedical Sciences Research Complex, School of Biology, University of St Andrews, St Andrews, Fife, United Kingdom
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3
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Antonelli T, Rajan A, Watson MD, Soltani S, Houghton J, Siemann GR, Zivanovic A, Bigi C, Edwards B, King PDC. Controlling the Charge Density Wave Transition in Single-Layer TiTe 2xSe 2(1-x) Alloys by Band Gap Engineering. Nano Lett 2024; 24:215-221. [PMID: 38117702 PMCID: PMC10786161 DOI: 10.1021/acs.nanolett.3c03776] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/02/2023] [Revised: 12/13/2023] [Accepted: 12/14/2023] [Indexed: 12/22/2023]
Abstract
Closing the band gap of a semiconductor into a semimetallic state gives a powerful potential route to tune the electronic energy gains that drive collective phases like charge density waves (CDWs) and excitonic insulator states. We explore this approach for the controversial CDW material monolayer (ML) TiSe2 by engineering its narrow band gap to the semimetallic limit of ML-TiTe2. Using molecular beam epitaxy, we demonstrate the growth of ML-TiTe2xSe2(1-x) alloys across the entire compositional range and unveil how the (2 × 2) CDW instability evolves through the normal state semiconductor-semimetal transition via in situ angle-resolved photoemission spectroscopy. Through model electronic structure calculations, we identify how this tunes the relative strength of excitonic and Peierls-like coupling, demonstrating band gap engineering as a powerful method for controlling the microscopic mechanisms underpinning the formation of collective states in two-dimensional materials.
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Affiliation(s)
- Tommaso Antonelli
- SUPA, School of Physics and
AstronomyUniversity of St Andrews, St Andrews KY16 9SS, United Kingdom
| | - Akhil Rajan
- SUPA, School of Physics and
AstronomyUniversity of St Andrews, St Andrews KY16 9SS, United Kingdom
| | - Matthew D. Watson
- SUPA, School of Physics and
AstronomyUniversity of St Andrews, St Andrews KY16 9SS, United Kingdom
| | | | - Joe Houghton
- SUPA, School of Physics and
AstronomyUniversity of St Andrews, St Andrews KY16 9SS, United Kingdom
| | - Gesa-Roxanne Siemann
- SUPA, School of Physics and
AstronomyUniversity of St Andrews, St Andrews KY16 9SS, United Kingdom
| | - Andela Zivanovic
- SUPA, School of Physics and
AstronomyUniversity of St Andrews, St Andrews KY16 9SS, United Kingdom
| | - Chiara Bigi
- SUPA, School of Physics and
AstronomyUniversity of St Andrews, St Andrews KY16 9SS, United Kingdom
| | - Brendan Edwards
- SUPA, School of Physics and
AstronomyUniversity of St Andrews, St Andrews KY16 9SS, United Kingdom
| | - Phil D. C. King
- SUPA, School of Physics and
AstronomyUniversity of St Andrews, St Andrews KY16 9SS, United Kingdom
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4
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Mazzola F, Enzner S, Eck P, Bigi C, Jugovac M, Cojocariu I, Feyer V, Shu Z, Pierantozzi GM, De Vita A, Carrara P, Fujii J, King PDC, Vinai G, Orgiani P, Cacho C, Watson MD, Rossi G, Vobornik I, Kong T, Di Sante D, Sangiovanni G, Panaccione G. Observation of Termination-Dependent Topological Connectivity in a Magnetic Weyl Kagome Lattice. Nano Lett 2023; 23:8035-8042. [PMID: 37638737 PMCID: PMC10510577 DOI: 10.1021/acs.nanolett.3c02022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/30/2023] [Revised: 08/21/2023] [Indexed: 08/29/2023]
Abstract
Engineering surfaces and interfaces of materials promises great potential in the field of heterostructures and quantum matter designers, with the opportunity to drive new many-body phases that are absent in the bulk compounds. Here, we focus on the magnetic Weyl kagome system Co3Sn2S2 and show how for the terminations of different samples the Weyl points connect differently, still preserving the bulk-boundary correspondence. Scanning tunneling microscopy has suggested such a scenario indirectly, and here, we probe the Fermiology of Co3Sn2S2 directly, by linking it to its real space surface distribution. By combining micro-ARPES and first-principles calculations, we measure the energy-momentum spectra and the Fermi surfaces of Co3Sn2S2 for different surface terminations and show the existence of topological features depending on the top-layer electronic environment. Our work helps to define a route for controlling bulk-derived topological properties by means of surface electrostatic potentials, offering a methodology for using Weyl kagome metals in responsive magnetic spintronics.
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Affiliation(s)
- Federico Mazzola
- Department
of Molecular Sciences and Nanosystems, Ca’
Foscari University of Venice, 30172 Venice, Italy
| | - Stefan Enzner
- Institut
für Theoretische Physik und Astrophysik and Würzburg-Dresden
Cluster of Excellence ct.qmat, Universität
Würzburg, 97074 Würzburg, Germany
| | - Philipp Eck
- Institut
für Theoretische Physik und Astrophysik and Würzburg-Dresden
Cluster of Excellence ct.qmat, Universität
Würzburg, 97074 Würzburg, Germany
| | - Chiara Bigi
- School
of Physics and Astronomy, University of
St Andrews, St Andrews KY16 9SS, United
Kingdom
| | - Matteo Jugovac
- Elettra
Sincrotrone Trieste S.C.p.A. S. S. 14, km 163.5, 34149 Trieste, Italy
| | - Iulia Cojocariu
- Elettra
Sincrotrone Trieste S.C.p.A. S. S. 14, km 163.5, 34149 Trieste, Italy
- Università degli studi di Trieste Via A. Valerio 2, 34127 Trieste, Italy
| | - Vitaliy Feyer
- Forschungszentrum Juelich GmBH PGI-6Leo Brandt Strasse, 52425 Juelich, Germany
| | - Zhixue Shu
- Department
of Physics, University of Arizona, Tucson, Arizona 85721, United States
| | - Gian Marco Pierantozzi
- Istituto
Officina dei Materiali, Consiglio Nazionale
delle Ricerche, Trieste I-34149, Italy
| | - Alessandro De Vita
- Dipartimento
di Fisica Universitá di Milano, Via Celoria 16, Milano 20133, Italy
| | - Pietro Carrara
- Dipartimento
di Fisica Universitá di Milano, Via Celoria 16, Milano 20133, Italy
| | - Jun Fujii
- Istituto
Officina dei Materiali, Consiglio Nazionale
delle Ricerche, Trieste I-34149, Italy
| | - Phil D. C. King
- School
of Physics and Astronomy, University of
St Andrews, St Andrews KY16 9SS, United
Kingdom
| | - Giovanni Vinai
- Istituto
Officina dei Materiali, Consiglio Nazionale
delle Ricerche, Trieste I-34149, Italy
| | - Pasquale Orgiani
- Istituto
Officina dei Materiali, Consiglio Nazionale
delle Ricerche, Trieste I-34149, Italy
| | - Cephise Cacho
- Diamond
Light
Source, Harwell Campus, Didcot OX11 0DE, United Kingdom
| | - Matthew D. Watson
- Diamond
Light
Source, Harwell Campus, Didcot OX11 0DE, United Kingdom
| | - Giorgio Rossi
- Dipartimento
di Fisica Universitá di Milano, Via Celoria 16, Milano 20133, Italy
| | - Ivana Vobornik
- Istituto
Officina dei Materiali, Consiglio Nazionale
delle Ricerche, Trieste I-34149, Italy
| | - Tai Kong
- Department
of Physics, University of Arizona, Tucson, Arizona 85721, United States
| | - Domenico Di Sante
- Department
of Physics and Astronomy, University of
Bologna, 40127 Bologna, Italy
- Center
for Computational Quantum Physics, Flatiron
Institute, 162 5th Avenue, New York, New York 10010, United States
| | - Giorgio Sangiovanni
- Institut
für Theoretische Physik und Astrophysik and Würzburg-Dresden
Cluster of Excellence ct.qmat, Universität
Würzburg, 97074 Würzburg, Germany
| | - Giancarlo Panaccione
- Istituto
Officina dei Materiali, Consiglio Nazionale
delle Ricerche, Trieste I-34149, Italy
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5
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Edwards B, Dowinton O, Hall AE, Murgatroyd PAE, Buchberger S, Antonelli T, Siemann GR, Rajan A, Morales EA, Zivanovic A, Bigi C, Belosludov RV, Polley CM, Carbone D, Mayoh DA, Balakrishnan G, Bahramy MS, King PDC. Giant valley-Zeeman coupling in the surface layer of an intercalated transition metal dichalcogenide. Nat Mater 2023; 22:459-465. [PMID: 36658327 DOI: 10.1038/s41563-022-01459-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/04/2022] [Accepted: 12/06/2022] [Indexed: 06/17/2023]
Abstract
Spin-valley locking is ubiquitous among transition metal dichalcogenides with local or global inversion asymmetry, in turn stabilizing properties such as Ising superconductivity, and opening routes towards 'valleytronics'. The underlying valley-spin splitting is set by spin-orbit coupling but can be tuned via the application of external magnetic fields or through proximity coupling. However, only modest changes have been realized to date. Here, we investigate the electronic structure of the V-intercalated transition metal dichalcogenide V1/3NbS2 using microscopic-area spatially resolved and angle-resolved photoemission spectroscopy. Our measurements and corresponding density functional theory calculations reveal that the bulk magnetic order induces a giant valley-selective Ising coupling exceeding 50 meV in the surface NbS2 layer, equivalent to application of a ~250 T magnetic field. This energy scale is of comparable magnitude to the intrinsic spin-orbit splittings, and indicates how coupling of local magnetic moments to itinerant states of a transition metal dichalcogenide monolayer provides a powerful route to controlling their valley-spin splittings.
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Affiliation(s)
- B Edwards
- SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews, UK
| | - O Dowinton
- Department of Physics and Astronomy, University of Manchester, Manchester, UK
| | - A E Hall
- Department of Physics, University of Warwick, Coventry, United Kingdom
| | - P A E Murgatroyd
- SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews, UK
| | - S Buchberger
- SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews, UK
- Max Planck Institute for Chemical Physics of Solids, Dresden, Germany
| | - T Antonelli
- SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews, UK
| | - G-R Siemann
- SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews, UK
| | - A Rajan
- SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews, UK
| | - E Abarca Morales
- SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews, UK
- Max Planck Institute for Chemical Physics of Solids, Dresden, Germany
| | - A Zivanovic
- SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews, UK
- Max Planck Institute for Chemical Physics of Solids, Dresden, Germany
| | - C Bigi
- SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews, UK
| | - R V Belosludov
- Institute for Materials Research, Tohoku University, Sendai, Japan
| | - C M Polley
- MAX IV Laboratory, Lund University, Lund, Sweden
| | - D Carbone
- MAX IV Laboratory, Lund University, Lund, Sweden
| | - D A Mayoh
- Department of Physics, University of Warwick, Coventry, United Kingdom
| | - G Balakrishnan
- Department of Physics, University of Warwick, Coventry, United Kingdom
| | - M S Bahramy
- Department of Physics and Astronomy, University of Manchester, Manchester, UK.
| | - P D C King
- SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews, UK.
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6
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Abarca Morales E, Siemann GR, Zivanovic A, Murgatroyd PAE, Marković I, Edwards B, Hooley CA, Sokolov DA, Kikugawa N, Cacho C, Watson MD, Kim TK, Hicks CW, Mackenzie AP, King PDC. Hierarchy of Lifshitz Transitions in the Surface Electronic Structure of Sr_{2}RuO_{4} under Uniaxial Compression. Phys Rev Lett 2023; 130:096401. [PMID: 36930931 DOI: 10.1103/physrevlett.130.096401] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/23/2022] [Accepted: 01/11/2023] [Indexed: 06/18/2023]
Abstract
We report the evolution of the electronic structure at the surface of the layered perovskite Sr_{2}RuO_{4} under large in-plane uniaxial compression, leading to anisotropic B_{1g} strains of ϵ_{xx}-ϵ_{yy}=-0.9±0.1%. From angle-resolved photoemission, we show how this drives a sequence of Lifshitz transitions, reshaping the low-energy electronic structure and the rich spectrum of van Hove singularities that the surface layer of Sr_{2}RuO_{4} hosts. From comparison to tight-binding modeling, we find that the strain is accommodated predominantly by bond-length changes rather than modifications of octahedral tilt and rotation angles. Our study sheds new light on the nature of structural distortions at oxide surfaces, and how targeted control of these can be used to tune density of state singularities to the Fermi level, in turn paving the way to the possible realization of rich collective states at the Sr_{2}RuO_{4} surface.
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Affiliation(s)
- Edgar Abarca Morales
- Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Strasse 40, 01187 Dresden, Germany
- SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews KY16 9SS, United Kingdom
| | - Gesa-R Siemann
- SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews KY16 9SS, United Kingdom
| | - Andela Zivanovic
- Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Strasse 40, 01187 Dresden, Germany
- SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews KY16 9SS, United Kingdom
| | - Philip A E Murgatroyd
- SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews KY16 9SS, United Kingdom
| | - Igor Marković
- Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Strasse 40, 01187 Dresden, Germany
- SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews KY16 9SS, United Kingdom
| | - Brendan Edwards
- SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews KY16 9SS, United Kingdom
| | - Chris A Hooley
- SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews KY16 9SS, United Kingdom
| | - Dmitry A Sokolov
- Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Strasse 40, 01187 Dresden, Germany
| | - Naoki Kikugawa
- National Institute for Materials Science, Tsukuba, Ibaraki 305-0003, Japan
| | - Cephise Cacho
- Diamond Light Source, Harwell Science and Innovation Campus, Didcot, OX11 ODE, United Kingdom
| | - Matthew D Watson
- Diamond Light Source, Harwell Science and Innovation Campus, Didcot, OX11 ODE, United Kingdom
| | - Timur K Kim
- Diamond Light Source, Harwell Science and Innovation Campus, Didcot, OX11 ODE, United Kingdom
| | - Clifford W Hicks
- Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Strasse 40, 01187 Dresden, Germany
- School of Physics and Astronomy, University of Birmingham, Birmingham B15 2TT, United Kingdom
| | - Andrew P Mackenzie
- Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Strasse 40, 01187 Dresden, Germany
- SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews KY16 9SS, United Kingdom
| | - Phil D C King
- SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews KY16 9SS, United Kingdom
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7
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Marques CA, Bahramy MS, Trainer C, Marković I, Watson MD, Mazzola F, Rajan A, Raub TD, King PDC, Wahl P. Tomographic mapping of the hidden dimension in quasi-particle interference. Nat Commun 2021; 12:6739. [PMID: 34795276 PMCID: PMC8602440 DOI: 10.1038/s41467-021-27082-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2021] [Accepted: 11/04/2021] [Indexed: 11/12/2022] Open
Abstract
Quasiparticle interference (QPI) imaging is well established to study the low-energy electronic structure in strongly correlated electron materials with unrivalled energy resolution. Yet, being a surface-sensitive technique, the interpretation of QPI only works well for anisotropic materials, where the dispersion in the direction perpendicular to the surface can be neglected and the quasiparticle interference is dominated by a quasi-2D electronic structure. Here, we explore QPI imaging of galena, a material with an electronic structure that does not exhibit pronounced anisotropy. We find that the quasiparticle interference signal is dominated by scattering vectors which are parallel to the surface plane however originate from bias-dependent cuts of the 3D electronic structure. We develop a formalism for the theoretical description of the QPI signal and demonstrate how this quasiparticle tomography can be used to obtain information about the 3D electronic structure and orbital character of the bands.
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Affiliation(s)
- C A Marques
- SUPA, School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews, Fife, KY16 9SS, UK
| | - M S Bahramy
- Department of Physics and Astronomy, The University of Manchester, Oxford Road, Manchester, M13 9PL, UK.
| | - C Trainer
- SUPA, School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews, Fife, KY16 9SS, UK
| | - I Marković
- SUPA, School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews, Fife, KY16 9SS, UK
- Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Strasse 40, 01187, Dresden, Germany
| | - M D Watson
- SUPA, School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews, Fife, KY16 9SS, UK
| | - F Mazzola
- SUPA, School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews, Fife, KY16 9SS, UK
| | - A Rajan
- SUPA, School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews, Fife, KY16 9SS, UK
| | - T D Raub
- School of Earth and Environmental Sciences, University of St Andrews, Irvine Building, St Andrews, KY16 9AL, UK
| | - P D C King
- SUPA, School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews, Fife, KY16 9SS, UK
| | - P Wahl
- SUPA, School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews, Fife, KY16 9SS, UK.
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8
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King PDC. Controlling topology with strain. Nat Mater 2021; 20:1046-1047. [PMID: 34321651 DOI: 10.1038/s41563-021-01043-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Affiliation(s)
- Phil D C King
- SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews, UK.
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9
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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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10
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Biswas D, Jones AJH, Majchrzak P, Choi BK, Lee TH, Volckaert K, Feng J, Marković I, Andreatta F, Kang CJ, Kim HJ, Lee IH, Jozwiak C, Rotenberg E, Bostwick A, Sanders CE, Zhang Y, Karras G, Chapman RT, Wyatt AS, Springate E, Miwa JA, Hofmann P, King PDC, Chang YJ, Lanatà N, Ulstrup S. Ultrafast Triggering of Insulator-Metal Transition in Two-Dimensional VSe 2. Nano Lett 2021; 21:1968-1975. [PMID: 33600187 DOI: 10.1021/acs.nanolett.0c04409] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
The transition-metal dichalcogenide VSe2 exhibits an increased charge density wave transition temperature and an emerging insulating phase when thinned to a single layer. Here, we investigate the interplay of electronic and lattice degrees of freedom that underpin these phases in single-layer VSe2 using ultrafast pump-probe photoemission spectroscopy. In the insulating state, we observe a light-induced closure of the energy gap, which we disentangle from the ensuing hot carrier dynamics by fitting a model spectral function to the time-dependent photoemission intensity. This procedure leads to an estimated time scale of 480 fs for the closure of the gap, which suggests that the phase transition in single-layer VSe2 is driven by electron-lattice interactions rather than by Mott-like electronic effects. The ultrafast optical switching of these interactions in SL VSe2 demonstrates the potential for controlling phase transitions in 2D materials with light.
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Affiliation(s)
- Deepnarayan Biswas
- Department of Physics and Astronomy, Interdisciplinary Nanoscience Center, Aarhus University, 8000 Aarhus C, Denmark
| | - Alfred J H Jones
- Department of Physics and Astronomy, Interdisciplinary Nanoscience Center, Aarhus University, 8000 Aarhus C, Denmark
| | - Paulina Majchrzak
- Department of Physics and Astronomy, Interdisciplinary Nanoscience Center, Aarhus University, 8000 Aarhus C, Denmark
- Central Laser Facility, STFC Rutherford Appleton Laboratory, Harwell 0 × 11 0QX, U.K
| | - Byoung Ki Choi
- Department of Physics, University of Seoul, Seoul 02504, Republic of Korea
| | - Tsung-Han Lee
- Department of Physics and Astronomy, Rutgers University, Piscataway, New Jersey 08856, United States
| | - Klara Volckaert
- Department of Physics and Astronomy, Interdisciplinary Nanoscience Center, Aarhus University, 8000 Aarhus C, Denmark
| | - Jiagui Feng
- SUPA, School of Physics and Astronomy, University of St. Andrews, St. Andrews KY16 9SS, U.K
- Suzhou Institute of Nano-Tech. and Nanobionics (SINANO), CAS, 398 Ruoshui Road, SEID, SIP, Suzhou 215123, China
| | - Igor Marković
- SUPA, School of Physics and Astronomy, University of St. Andrews, St. Andrews KY16 9SS, U.K
- Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, 01187 Dresden, Germany
| | - Federico Andreatta
- Department of Physics and Astronomy, Interdisciplinary Nanoscience Center, Aarhus University, 8000 Aarhus C, Denmark
| | - Chang-Jong Kang
- Department of Physics and Astronomy, Rutgers University, Piscataway, New Jersey 08856, United States
| | - Hyuk Jin Kim
- Department of Physics, University of Seoul, Seoul 02504, Republic of Korea
| | - In Hak Lee
- Department of Physics, University of Seoul, Seoul 02504, Republic of Korea
| | - Chris Jozwiak
- Advanced Light Source, E. O. Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Eli Rotenberg
- Advanced Light Source, E. O. Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Aaron Bostwick
- Advanced Light Source, E. O. Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Charlotte E Sanders
- Central Laser Facility, STFC Rutherford Appleton Laboratory, Harwell 0 × 11 0QX, U.K
| | - Yu Zhang
- Central Laser Facility, STFC Rutherford Appleton Laboratory, Harwell 0 × 11 0QX, U.K
| | - Gabriel Karras
- Central Laser Facility, STFC Rutherford Appleton Laboratory, Harwell 0 × 11 0QX, U.K
| | - Richard T Chapman
- Central Laser Facility, STFC Rutherford Appleton Laboratory, Harwell 0 × 11 0QX, U.K
| | - Adam S Wyatt
- Central Laser Facility, STFC Rutherford Appleton Laboratory, Harwell 0 × 11 0QX, U.K
| | - Emma Springate
- Central Laser Facility, STFC Rutherford Appleton Laboratory, Harwell 0 × 11 0QX, U.K
| | - Jill A Miwa
- Department of Physics and Astronomy, Interdisciplinary Nanoscience Center, Aarhus University, 8000 Aarhus C, Denmark
| | - Philip Hofmann
- Department of Physics and Astronomy, Interdisciplinary Nanoscience Center, Aarhus University, 8000 Aarhus C, Denmark
| | - Phil D C King
- SUPA, School of Physics and Astronomy, University of St. Andrews, St. Andrews KY16 9SS, U.K
| | - Young Jun Chang
- Department of Physics, University of Seoul, Seoul 02504, Republic of Korea
- Department of Smart Cities, University of Seoul, Seoul, 02504, Republic of Korea
| | - Nicola Lanatà
- Department of Physics and Astronomy, Interdisciplinary Nanoscience Center, Aarhus University, 8000 Aarhus C, Denmark
- Nordita, KTH Royal Institute of Technology and Stockholm University, Roslagstullsbacken 23, 10691 Stockholm, Sweden
| | - Søren Ulstrup
- Department of Physics and Astronomy, Interdisciplinary Nanoscience Center, Aarhus University, 8000 Aarhus C, Denmark
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11
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Marković I, Hooley CA, Clark OJ, Mazzola F, Watson MD, Riley JM, Volckaert K, Underwood K, Dyer MS, Murgatroyd PAE, Murphy KJ, Fèvre PL, Bertran F, Fujii J, Vobornik I, Wu S, Okuda T, Alaria J, King PDC. Weyl-like points from band inversions of spin-polarised surface states in NbGeSb. Nat Commun 2019; 10:5485. [PMID: 31792208 PMCID: PMC6888910 DOI: 10.1038/s41467-019-13464-z] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2019] [Accepted: 11/08/2019] [Indexed: 11/09/2022] Open
Abstract
Band inversions are key to stabilising a variety of novel electronic states in solids, from topological surface states to the formation of symmetry-protected three-dimensional Dirac and Weyl points and nodal-line semimetals. Here, we create a band inversion not of bulk states, but rather between manifolds of surface states. We realise this by aliovalent substitution of Nb for Zr and Sb for S in the ZrSiS family of nonsymmorphic semimetals. Using angle-resolved photoemission and density-functional theory, we show how two pairs of surface states, known from ZrSiS, are driven to intersect each other near the Fermi level in NbGeSb, and to develop pronounced spin splittings. We demonstrate how mirror symmetry leads to protected crossing points in the resulting spin-orbital entangled surface band structure, thereby stabilising surface state analogues of three-dimensional Weyl points. More generally, our observations suggest new opportunities for engineering topologically and symmetry-protected states via band inversions of surface states.
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Affiliation(s)
- I Marković
- SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews, KY16 9SS, United Kingdom.,Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Strasse 40, 01187, Dresden, Germany
| | - C A Hooley
- SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews, KY16 9SS, United Kingdom
| | - O J Clark
- SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews, KY16 9SS, United Kingdom
| | - F Mazzola
- SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews, KY16 9SS, United Kingdom
| | - M D Watson
- SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews, KY16 9SS, United Kingdom
| | - J M Riley
- SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews, KY16 9SS, United Kingdom
| | - K Volckaert
- SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews, KY16 9SS, United Kingdom
| | - K Underwood
- SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews, KY16 9SS, United Kingdom
| | - M S Dyer
- Department of Chemistry, University of Liverpool, Liverpool, L69 7ZD, United Kingdom
| | - P A E Murgatroyd
- Department of Physics, University of Liverpool, Liverpool, L69 7ZE, United Kingdom
| | - K J Murphy
- Department of Physics, University of Liverpool, Liverpool, L69 7ZE, United Kingdom
| | - P Le Fèvre
- Synchrotron SOLEIL, CNRS-CEA, L'Orme des Merisiers, Saint-Aubin-BP48, 91192, Gif-sur-Yvette, France
| | - F Bertran
- Synchrotron SOLEIL, CNRS-CEA, L'Orme des Merisiers, Saint-Aubin-BP48, 91192, Gif-sur-Yvette, France
| | - J Fujii
- Istituto Officina dei Materiali (IOM)-CNR, Laboratorio TASC, Area Science Park, S.S.14, Km 163.5, 34149, Trieste, Italy
| | - I Vobornik
- Istituto Officina dei Materiali (IOM)-CNR, Laboratorio TASC, Area Science Park, S.S.14, Km 163.5, 34149, Trieste, Italy
| | - S Wu
- Graduate School of Science, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, 739-8526, Japan
| | - T Okuda
- Hiroshima Synchrotron Radiation Center, Hiroshima University, 2-313 Kagamiyama, Higashi-Hiroshima, 739-0046, Japan
| | - J Alaria
- Department of Physics, University of Liverpool, Liverpool, L69 7ZE, United Kingdom
| | - P D C King
- SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews, KY16 9SS, United Kingdom.
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12
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Feng J, Biswas D, Rajan A, Watson MD, Mazzola F, Clark OJ, Underwood K, Marković I, McLaren M, Hunter A, Burn DM, Duffy LB, Barua S, Balakrishnan G, Bertran F, Le Fèvre P, Kim TK, van der Laan G, Hesjedal T, Wahl P, King PDC. Electronic Structure and Enhanced Charge-Density Wave Order of Monolayer VSe 2. Nano Lett 2018; 18:4493-4499. [PMID: 29912565 DOI: 10.1021/acs.nanolett.8b01649] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
How the interacting electronic states and phases of layered transition-metal dichalcogenides evolve when thinned to the single-layer limit is a key open question in the study of two-dimensional materials. Here, we use angle-resolved photoemission to investigate the electronic structure of monolayer VSe2 grown on bilayer graphene/SiC. While the global electronic structure is similar to that of bulk VSe2, we show that, for the monolayer, pronounced energy gaps develop over the entire Fermi surface with decreasing temperature below Tc = 140 ± 5 K, concomitant with the emergence of charge-order superstructures evident in low-energy electron diffraction. These observations point to a charge-density wave instability in the monolayer that is strongly enhanced over that of the bulk. Moreover, our measurements of both the electronic structure and of X-ray magnetic circular dichroism reveal no signatures of a ferromagnetic ordering, in contrast to the results of a recent experimental study as well as expectations from density functional theory. Our study thus points to a delicate balance that can be realized between competing interacting states and phases in monolayer transition-metal dichalcogenides.
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Affiliation(s)
- Jiagui Feng
- SUPA, School of Physics and Astronomy , University of St. Andrews , St. Andrews KY16 9SS , United Kingdom
- Suzhou Institute of Nano-Technology and Nanobionics (SINANO), CAS , 398 Ruoshui Road , SEID, SIP, Suzhou 215123 , China
| | - Deepnarayan Biswas
- SUPA, School of Physics and Astronomy , University of St. Andrews , St. Andrews KY16 9SS , United Kingdom
| | - Akhil Rajan
- SUPA, School of Physics and Astronomy , University of St. Andrews , St. Andrews KY16 9SS , United Kingdom
| | - Matthew D Watson
- SUPA, School of Physics and Astronomy , University of St. Andrews , St. Andrews KY16 9SS , United Kingdom
| | - Federico Mazzola
- SUPA, School of Physics and Astronomy , University of St. Andrews , St. Andrews KY16 9SS , United Kingdom
| | - Oliver J Clark
- SUPA, School of Physics and Astronomy , University of St. Andrews , St. Andrews KY16 9SS , United Kingdom
| | - Kaycee Underwood
- SUPA, School of Physics and Astronomy , University of St. Andrews , St. Andrews KY16 9SS , United Kingdom
| | - Igor Marković
- SUPA, School of Physics and Astronomy , University of St. Andrews , St. Andrews KY16 9SS , United Kingdom
- Max Planck Institute for Chemical Physics of Solids , Nöthnitzer Straße 40 , 01187 Dresden , Germany
| | - Martin McLaren
- SUPA, School of Physics and Astronomy , University of St. Andrews , St. Andrews KY16 9SS , United Kingdom
| | - Andrew Hunter
- SUPA, School of Physics and Astronomy , University of St. Andrews , St. Andrews KY16 9SS , United Kingdom
| | - David M Burn
- Magnetic Spectroscopy Group, Diamond Light Source , Didcot OX11 0DE , United Kingdom
| | - Liam B Duffy
- Department of Physics , University of Oxford , Oxford OX1 3PU , United Kingdom
- ISIS, STFC, Rutherford Appleton Laboratory , Didcot OX11 0QX , United Kingdom
| | - Sourabh Barua
- Department of Physics , University of Warwick , Coventry CV4 7AL , United Kingdom
| | - Geetha Balakrishnan
- Department of Physics , University of Warwick , Coventry CV4 7AL , United Kingdom
| | - François Bertran
- Synchrotron SOLEIL, CNRS-CEA , L'Orme des Merisiers, Saint-Aubin-BP48 , 91192 Gif-sur-Yvette , France
| | - Patrick Le Fèvre
- Synchrotron SOLEIL, CNRS-CEA , L'Orme des Merisiers, Saint-Aubin-BP48 , 91192 Gif-sur-Yvette , France
| | - Timur K Kim
- Diamond Light Source , Harwell Campus , Didcot OX11 0DE , United Kingdom
| | - Gerrit van der Laan
- Magnetic Spectroscopy Group, Diamond Light Source , Didcot OX11 0DE , United Kingdom
| | - Thorsten Hesjedal
- Department of Physics , University of Oxford , Oxford OX1 3PU , United Kingdom
| | - Peter Wahl
- SUPA, School of Physics and Astronomy , University of St. Andrews , St. Andrews KY16 9SS , United Kingdom
| | - Phil D C King
- SUPA, School of Physics and Astronomy , University of St. Andrews , St. Andrews KY16 9SS , United Kingdom
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13
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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] [What about the content of this article? (0)] [Affiliation(s)] [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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14
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Clark OJ, Neat MJ, Okawa K, Bawden L, Marković I, Mazzola F, Feng J, Sunko V, Riley JM, Meevasana W, Fujii J, Vobornik I, Kim TK, Hoesch M, Sasagawa T, Wahl P, Bahramy MS, King PDC. Fermiology and Superconductivity of Topological Surface States in PdTe_{2}. Phys Rev Lett 2018; 120:156401. [PMID: 29756894 DOI: 10.1103/physrevlett.120.156401] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/14/2017] [Revised: 01/17/2018] [Indexed: 05/12/2023]
Abstract
We study the low-energy surface electronic structure of the transition-metal dichalcogenide superconductor PdTe_{2} by spin- and angle-resolved photoemission, scanning tunneling microscopy, and density-functional theory-based supercell calculations. Comparing PdTe_{2} with its sister compound PtSe_{2}, we demonstrate how enhanced interlayer hopping in the Te-based material drives a band inversion within the antibonding p-orbital manifold well above the Fermi level. We show how this mediates spin-polarized topological surface states which form rich multivalley Fermi surfaces with complex spin textures. Scanning tunneling spectroscopy reveals type-II superconductivity at the surface, and moreover shows no evidence for an unconventional component of its superconducting order parameter, despite the presence of topological surface states.
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Affiliation(s)
- O J Clark
- SUPA, School of Physics and Astronomy, University of St. Andrews, St. Andrews KY16 9SS, United Kingdom
| | - M J Neat
- SUPA, School of Physics and Astronomy, University of St. Andrews, St. Andrews KY16 9SS, United Kingdom
| | - K Okawa
- Materials and Structures Laboratory, Tokyo Institute of Technology, Kanagawa 226-8503, Japan
| | - L Bawden
- SUPA, School of Physics and Astronomy, University of St. Andrews, St. Andrews KY16 9SS, United Kingdom
| | - I Marković
- SUPA, School of Physics and Astronomy, University of St. Andrews, St. Andrews KY16 9SS, United Kingdom
- Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, 01187 Dresden, Germany
| | - F Mazzola
- SUPA, School of Physics and Astronomy, University of St. Andrews, St. Andrews KY16 9SS, United Kingdom
| | - J Feng
- SUPA, School of Physics and Astronomy, University of St. Andrews, St. Andrews KY16 9SS, United Kingdom
- Suzhou Institute of Nano-Tech. and Nanobionics (SINANO), CAS, 398 Ruoshui Road, SEID, SIP, Suzhou 215123, China
| | - V Sunko
- SUPA, School of Physics and Astronomy, University of St. Andrews, St. Andrews KY16 9SS, United Kingdom
- Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, 01187 Dresden, Germany
| | - J M Riley
- SUPA, School of Physics and Astronomy, University of St. Andrews, St. Andrews KY16 9SS, United Kingdom
- Diamond Light Source, Harwell Campus, Didcot OX11 0DE, United Kingdom
| | - W Meevasana
- School of Physics and Center of Excellence on Advanced Functional Materials, Suranaree University of Technology, Nakhon Ratchasima, 30000, Thailand
- ThEP, Commission of Higher Education, Bangkok 10400, Thailand
| | - J Fujii
- Istituto Officina dei Materiali (IOM)-CNR, Laboratorio TASC, in Area Science Park, S.S.14, Km 163.5, I-34149 Trieste, Italy
| | - I Vobornik
- Istituto Officina dei Materiali (IOM)-CNR, Laboratorio TASC, in Area Science Park, S.S.14, Km 163.5, I-34149 Trieste, Italy
| | - T K Kim
- Diamond Light Source, Harwell Campus, Didcot OX11 0DE, United Kingdom
| | - M Hoesch
- Diamond Light Source, Harwell Campus, Didcot OX11 0DE, United Kingdom
| | - T Sasagawa
- Materials and Structures Laboratory, Tokyo Institute of Technology, Kanagawa 226-8503, Japan
| | - P Wahl
- SUPA, School of Physics and Astronomy, University of St. Andrews, St. Andrews KY16 9SS, United Kingdom
| | - M S Bahramy
- Quantum-Phase Electronics Center and Department of Applied Physics, The University of Tokyo, Tokyo 113-8656, Japan
- RIKEN center for Emergent Matter Science (CEMS), Wako 351-0198, Japan
| | - P D C King
- SUPA, School of Physics and Astronomy, University of St. Andrews, St. Andrews KY16 9SS, United Kingdom
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15
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Sunko V, Rosner H, Kushwaha P, Khim S, Mazzola F, Bawden L, Clark OJ, Riley JM, Kasinathan D, Haverkort MW, Kim TK, Hoesch M, Fujii J, Vobornik I, Mackenzie AP, King PDC. Maximal Rashba-like spin splitting via kinetic-energy-coupled inversion-symmetry breaking. Nature 2018; 549:492-496. [PMID: 28959958 DOI: 10.1038/nature23898] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2017] [Accepted: 07/26/2017] [Indexed: 11/09/2022]
Abstract
Engineering and enhancing the breaking of inversion symmetry in solids-that is, allowing electrons to differentiate between 'up' and 'down'-is a key goal in condensed-matter physics and materials science because it can be used to stabilize states that are of fundamental interest and also have potential practical applications. Examples include improved ferroelectrics for memory devices and materials that host Majorana zero modes for quantum computing. Although inversion symmetry is naturally broken in several crystalline environments, such as at surfaces and interfaces, maximizing the influence of this effect on the electronic states of interest remains a challenge. Here we present a mechanism for realizing a much larger coupling of inversion-symmetry breaking to itinerant surface electrons than is typically achieved. The key element is a pronounced asymmetry of surface hopping energies-that is, a kinetic-energy-coupled inversion-symmetry breaking, the energy scale of which is a substantial fraction of the bandwidth. Using spin- and angle-resolved photoemission spectroscopy, we demonstrate that such a strong inversion-symmetry breaking, when combined with spin-orbit interactions, can mediate Rashba-like spin splittings that are much larger than would typically be expected. The energy scale of the inversion-symmetry breaking that we achieve is so large that the spin splitting in the CoO2- and RhO2-derived surface states of delafossite oxides becomes controlled by the full atomic spin-orbit coupling of the 3d and 4d transition metals, resulting in some of the largest known Rashba-like spin splittings. The core structural building blocks that facilitate the bandwidth-scaled inversion-symmetry breaking are common to numerous materials. Our findings therefore provide opportunities for creating spin-textured states and suggest routes to interfacial control of inversion-symmetry breaking in designer heterostructures of oxides and other material classes.
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Affiliation(s)
- Veronika Sunko
- SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews KY16 9SS, UK.,Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, 01187 Dresden, Germany
| | - H Rosner
- Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, 01187 Dresden, Germany
| | - P Kushwaha
- Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, 01187 Dresden, Germany
| | - S Khim
- Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, 01187 Dresden, Germany
| | - F Mazzola
- SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews KY16 9SS, UK
| | - L Bawden
- SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews KY16 9SS, UK
| | - O J Clark
- SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews KY16 9SS, UK
| | - 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
| | - D Kasinathan
- Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, 01187 Dresden, Germany
| | - M W Haverkort
- Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, 01187 Dresden, Germany.,Institute for Theoretical Physics, Heidelberg University, Philosophenweg 19, 69120 Heidelberg, Germany
| | - T K Kim
- Diamond Light Source, Harwell Campus, Didcot OX11 0DE, UK
| | - M Hoesch
- Diamond Light Source, Harwell Campus, Didcot OX11 0DE, UK
| | - J Fujii
- Istituto Officina dei Materiali (IOM)-CNR, Laboratorio TASC, Area Science Park, S.S.14, Km 163.5, 34149 Trieste, Italy
| | - I Vobornik
- Istituto Officina dei Materiali (IOM)-CNR, Laboratorio TASC, Area Science Park, S.S.14, Km 163.5, 34149 Trieste, Italy
| | - A P Mackenzie
- SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews KY16 9SS, UK.,Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, 01187 Dresden, Germany
| | - P D C King
- SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews KY16 9SS, UK
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16
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Bahramy MS, Clark OJ, Yang BJ, Feng J, Bawden L, Riley JM, Marković I, Mazzola F, Sunko V, Biswas D, Cooil SP, Jorge M, Wells JW, Leandersson M, Balasubramanian T, Fujii J, Vobornik I, Rault JE, Kim TK, Hoesch M, Okawa K, Asakawa M, Sasagawa T, Eknapakul T, Meevasana W, King PDC. Ubiquitous formation of bulk Dirac cones and topological surface states from a single orbital manifold in transition-metal dichalcogenides. Nat Mater 2018; 17:21-28. [PMID: 29180775 DOI: 10.1038/nmat5031] [Citation(s) in RCA: 57] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/10/2017] [Accepted: 10/13/2017] [Indexed: 05/12/2023]
Abstract
Transition-metal dichalcogenides (TMDs) are renowned for their rich and varied bulk properties, while their single-layer variants have become one of the most prominent examples of two-dimensional materials beyond graphene. Their disparate ground states largely depend on transition metal d-electron-derived electronic states, on which the vast majority of attention has been concentrated to date. Here, we focus on the chalcogen-derived states. From density-functional theory calculations together with spin- and angle-resolved photoemission, we find that these generically host a co-existence of type-I and type-II three-dimensional bulk Dirac fermions as well as ladders of topological surface states and surface resonances. We demonstrate how these naturally arise within a single p-orbital manifold as a general consequence of a trigonal crystal field, and as such can be expected across a large number of compounds. Already, we demonstrate their existence in six separate TMDs, opening routes to tune, and ultimately exploit, their topological physics.
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Affiliation(s)
- M S Bahramy
- Quantum-Phase Electronics Center and Department of Applied Physics, University of Tokyo, Tokyo 113-8656, Japan
- RIKEN center for Emergent Matter Science (CEMS), Wako 351-0198, Japan
| | - O J Clark
- SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews, Fife KY16 9SS, UK
| | - B-J Yang
- Department of Physics and Astronomy, Seoul National University, Seoul 08826, Korea
- Center for Correlated Electron Systems, Institute for Basic Science (IBS), Seoul 08826, Korea
- Center for Theoretical Physics (CTP), Seoul National University, Seoul 08826, Korea
| | - J Feng
- SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews, Fife KY16 9SS, UK
- Suzhou Institute of Nano-Tech and Nano-Bionics (SINANO) CAS, 398 Ruoshi Road, SEID, SIP, Suzhou 215123, China
| | - L Bawden
- SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews, Fife KY16 9SS, UK
| | - J M Riley
- SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews, Fife KY16 9SS, UK
- Diamond Light Source, Harwell Campus, Didcot OX11 0DE, UK
| | - I Marković
- SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews, Fife KY16 9SS, UK
- Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, 01187 Dresden, Germany
| | - F Mazzola
- SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews, Fife KY16 9SS, UK
| | - V Sunko
- SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews, Fife KY16 9SS, UK
- Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, 01187 Dresden, Germany
| | - D Biswas
- SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews, Fife KY16 9SS, UK
| | - S P Cooil
- Center for Quantum Spintronics, Department of Physics, Norwegian University of Science and Technology, NO-7491 Trondheim, Norway
| | - M Jorge
- Center for Quantum Spintronics, Department of Physics, Norwegian University of Science and Technology, NO-7491 Trondheim, Norway
| | - J W Wells
- Center for Quantum Spintronics, Department of Physics, Norwegian University of Science and Technology, NO-7491 Trondheim, Norway
| | - M Leandersson
- MAX IV Laboratory, Lund University, PO Box 118, 221 00 Lund, Sweden
| | | | - J Fujii
- Istituto Officina dei Materiali (IOM)-CNR, Laboratorio TASC, in Area Science Park, S.S.14, Km 163.5, I-34149 Trieste, Italy
| | - I Vobornik
- Istituto Officina dei Materiali (IOM)-CNR, Laboratorio TASC, in Area Science Park, S.S.14, Km 163.5, I-34149 Trieste, Italy
| | - J E Rault
- Synchrotron SOLEIL, CNRS-CEA, L'Orme des Merisiers, Saint-Aubin-BP48, 91192 Gif-sur-Yvette, France
| | - T K Kim
- Diamond Light Source, Harwell Campus, Didcot OX11 0DE, UK
| | - M Hoesch
- Diamond Light Source, Harwell Campus, Didcot OX11 0DE, UK
| | - K Okawa
- Laboratory for Materials and Structures, Tokyo Institute of Technology, Kanagawa 226-8503, Japan
| | - M Asakawa
- Laboratory for Materials and Structures, Tokyo Institute of Technology, Kanagawa 226-8503, Japan
| | - T Sasagawa
- Laboratory for Materials and Structures, Tokyo Institute of Technology, Kanagawa 226-8503, Japan
| | - T Eknapakul
- School of Physics and Center of Excellence on Advanced Functional Materials, Suranaree University of Technology, Nakhon Ratchasima 30000, Thailand
| | - W Meevasana
- School of Physics and Center of Excellence on Advanced Functional Materials, Suranaree University of Technology, Nakhon Ratchasima 30000, Thailand
- ThEP, Commission of Higher Education, Bangkok 10400, Thailand
| | - P D C King
- SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews, Fife KY16 9SS, UK
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17
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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. Nat Mater 2016; 15:835-839. [PMID: 27064529 DOI: 10.1038/nmat4623] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [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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18
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Ulstrup S, Čabo AG, Miwa JA, Riley JM, Grønborg SS, Johannsen JC, Cacho C, Alexander O, Chapman RT, Springate E, Bianchi M, Dendzik M, Lauritsen JV, King PDC, Hofmann P. Ultrafast Band Structure Control of a Two-Dimensional Heterostructure. ACS Nano 2016; 10:6315-6322. [PMID: 27267820 DOI: 10.1021/acsnano.6b02622] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The electronic structure of two-dimensional (2D) semiconductors can be significantly altered by screening effects, either from free charge carriers in the material or by environmental screening from the surrounding medium. The physical properties of 2D semiconductors placed in a heterostructure with other 2D materials are therefore governed by a complex interplay of both intra- and interlayer interactions. Here, using time- and angle-resolved photoemission, we are able to isolate both the layer-resolved band structure and, more importantly, the transient band structure evolution of a model 2D heterostructure formed of a single layer of MoS2 on graphene. Our results reveal a pronounced renormalization of the quasiparticle gap of the MoS2 layer. Following optical excitation, the band gap is reduced by up to ∼400 meV on femtosecond time scales due to a persistence of strong electronic interactions despite the environmental screening by the n-doped graphene. This points to a large degree of tunability of both the electronic structure and the electron dynamics for 2D semiconductors embedded in a van der Waals-bonded heterostructure.
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Affiliation(s)
- Søren Ulstrup
- Advanced Light Source, E. O. Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States
| | - Antonija Grubišić Čabo
- Department of Physics and Astronomy, Interdisciplinary Nanoscience Center, Aarhus University , 8000 Aarhus C, Denmark
| | - Jill A Miwa
- Department of Physics and Astronomy, Interdisciplinary Nanoscience Center, Aarhus University , 8000 Aarhus C, Denmark
| | - Jonathon M Riley
- SUPA, School of Physics and Astronomy, University of St. Andrews , St. Andrews KY16 9AJ, United Kingdom
| | - Signe S Grønborg
- Department of Physics and Astronomy, Interdisciplinary Nanoscience Center, Aarhus University , 8000 Aarhus C, Denmark
| | - Jens C Johannsen
- Institute of Condensed Matter Physics, École Polytechnique Fédérale de Lausanne (EPFL) , 1015 Lausanne, Switzerland
| | - Cephise Cacho
- Central Laser Facility, STFC Rutherford Appleton Laboratory , Harwell OX11 0QX, United Kingdom
| | - Oliver Alexander
- Central Laser Facility, STFC Rutherford Appleton Laboratory , Harwell OX11 0QX, United Kingdom
| | - Richard T Chapman
- Central Laser Facility, STFC Rutherford Appleton Laboratory , Harwell OX11 0QX, United Kingdom
| | - Emma Springate
- Central Laser Facility, STFC Rutherford Appleton Laboratory , Harwell OX11 0QX, United Kingdom
| | - Marco Bianchi
- Department of Physics and Astronomy, Interdisciplinary Nanoscience Center, Aarhus University , 8000 Aarhus C, Denmark
| | - Maciej Dendzik
- Department of Physics and Astronomy, Interdisciplinary Nanoscience Center, Aarhus University , 8000 Aarhus C, Denmark
| | - Jeppe V Lauritsen
- Department of Physics and Astronomy, Interdisciplinary Nanoscience Center, Aarhus University , 8000 Aarhus C, Denmark
| | - Phil D C King
- SUPA, School of Physics and Astronomy, University of St. Andrews , St. Andrews KY16 9AJ, United Kingdom
| | - Philip Hofmann
- Department of Physics and Astronomy, Interdisciplinary Nanoscience Center, Aarhus University , 8000 Aarhus C, Denmark
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19
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Burganov B, Adamo C, Mulder A, Uchida M, King PDC, Harter JW, Shai DE, Gibbs AS, Mackenzie AP, Uecker R, Bruetzam M, Beasley MR, Fennie CJ, Schlom DG, Shen KM. Strain Control of Fermiology and Many-Body Interactions in Two-Dimensional Ruthenates. Phys Rev Lett 2016; 116:197003. [PMID: 27232037 DOI: 10.1103/physrevlett.116.197003] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/20/2016] [Indexed: 06/05/2023]
Abstract
Here we demonstrate how the Fermi surface topology and quantum many-body interactions can be manipulated via epitaxial strain in the spin-triplet superconductor Sr_{2}RuO_{4} and its isoelectronic counterpart Ba_{2}RuO_{4} using oxide molecular beam epitaxy, in situ angle-resolved photoemission spectroscopy, and transport measurements. Near the topological transition of the γ Fermi surface sheet, we observe clear signatures of critical fluctuations, while the quasiparticle mass enhancement is found to increase rapidly and monotonically with increasing Ru-O bond distance. Our work demonstrates the possibilities for using epitaxial strain as a disorder-free means of manipulating emergent properties, many-body interactions, and potentially the superconductivity in correlated materials.
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Affiliation(s)
- B Burganov
- Laboratory of Atomic and Solid State Physics, Department of Physics, Cornell University, Ithaca, New York 14853, USA
| | - C Adamo
- Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14853, USA
- Department of Applied Physics, Stanford University, Stanford, California 94305, USA
| | - A Mulder
- School of Applied and Engineering Physics, Cornell University, Ithaca, New York 14853, USA
| | - M Uchida
- Laboratory of Atomic and Solid State Physics, Department of Physics, Cornell University, Ithaca, New York 14853, USA
| | - P D C King
- Laboratory of Atomic and Solid State Physics, Department of Physics, Cornell University, Ithaca, New York 14853, USA
- School of Physics and Astronomy, University of St Andrews, St Andrews, Fife KY16 9SS, United Kingdom
- Kavli Institute at Cornell for Nanoscale Science, Ithaca, New York 14853, USA
| | - J W Harter
- Laboratory of Atomic and Solid State Physics, Department of Physics, Cornell University, Ithaca, New York 14853, USA
| | - D E Shai
- Laboratory of Atomic and Solid State Physics, Department of Physics, Cornell University, Ithaca, New York 14853, USA
| | - A S Gibbs
- Max Planck Institute for Solid State Research, 70569 Stuttgart, Germany
| | - A P Mackenzie
- School of Physics and Astronomy, University of St Andrews, St Andrews, Fife KY16 9SS, United Kingdom
- Max Planck Institute for Chemical Physics of Solids, D-01187 Dresden, Germany
| | - R Uecker
- Leibniz Institute for Crystal Growth, D-12489 Berlin, Germany
| | - M Bruetzam
- Leibniz Institute for Crystal Growth, D-12489 Berlin, Germany
| | - M R Beasley
- Department of Applied Physics, Stanford University, Stanford, California 94305, USA
| | - C J Fennie
- School of Applied and Engineering Physics, Cornell University, Ithaca, New York 14853, USA
| | - D G Schlom
- Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14853, USA
- Kavli Institute at Cornell for Nanoscale Science, Ithaca, New York 14853, USA
| | - K M Shen
- Laboratory of Atomic and Solid State Physics, Department of Physics, Cornell University, Ithaca, New York 14853, USA
- Kavli Institute at Cornell for Nanoscale Science, Ithaca, New York 14853, USA
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20
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Riley JM, Meevasana W, Bawden L, Asakawa M, Takayama T, Eknapakul T, Kim TK, Hoesch M, Mo SK, Takagi H, Sasagawa T, Bahramy MS, King PDC. Negative electronic compressibility and tunable spin splitting in WSe2. Nat Nanotechnol 2015; 10:1043-1047. [PMID: 26389661 DOI: 10.1038/nnano.2015.217] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/20/2015] [Accepted: 08/20/2015] [Indexed: 06/05/2023]
Abstract
Tunable bandgaps, extraordinarily large exciton-binding energies, strong light-matter coupling and a locking of the electron spin with layer and valley pseudospins have established transition-metal dichalcogenides (TMDs) as a unique class of two-dimensional (2D) semiconductors with wide-ranging practical applications. Using angle-resolved photoemission (ARPES), we show here that doping electrons at the surface of the prototypical strong spin-orbit TMD WSe2, akin to applying a gate voltage in a transistor-type device, induces a counterintuitive lowering of the surface chemical potential concomitant with the formation of a multivalley 2D electron gas (2DEG). These measurements provide a direct spectroscopic signature of negative electronic compressibility (NEC), a result of electron-electron interactions, which we find persists to carrier densities approximately three orders of magnitude higher than in typical semiconductor 2DEGs that exhibit this effect. An accompanying tunable spin splitting of the valence bands further reveals a complex interplay between single-particle band-structure evolution and many-body interactions in electrostatically doped TMDs. Understanding and exploiting this will open up new opportunities for advanced electronic and quantum-logic devices.
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Affiliation(s)
- J M Riley
- SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews, Fife KY16 9SS, UK
- Diamond Light Source, Harwell Campus, Didcot OX11 0DE, UK
| | - W Meevasana
- School of Physics, Suranaree University of Technology, Nakhon Ratchasima 30000, Thailand
- NANOTEC-SUT Center of Excellence on Advanced Functional Nanomaterials, Suranaree University of Technology, Nakhon Ratchasima 30000, Thailand
| | - L Bawden
- SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews, Fife KY16 9SS, UK
| | - M Asakawa
- Materials and Structures Laboratory, Tokyo Institute of Technology, Kanagawa 226-8503, Japan
| | - T Takayama
- Department of Physics, University of Tokyo, Hongo, Tokyo 113-0033, Japan
- Max Planck Institute for Solid State Research, Stuttgart 70569, Germany
| | - T Eknapakul
- School of Physics, Suranaree University of Technology, Nakhon Ratchasima 30000, Thailand
| | - T K Kim
- Diamond Light Source, Harwell Campus, Didcot OX11 0DE, UK
| | - M Hoesch
- Diamond Light Source, Harwell Campus, Didcot OX11 0DE, UK
| | - S-K Mo
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley California 94720, USA
| | - H Takagi
- Department of Physics, University of Tokyo, Hongo, Tokyo 113-0033, Japan
- Max Planck Institute for Solid State Research, Stuttgart 70569, Germany
| | - T Sasagawa
- Materials and Structures Laboratory, Tokyo Institute of Technology, Kanagawa 226-8503, Japan
| | - M S Bahramy
- Quantum-Phase Electronics Center and Department of Applied Physics, The University of Tokyo, Tokyo 113-8656, Japan
- RIKEN Center for Emergent Matter Science (CEMS), Wako 351-0198, Japan
| | - P D C King
- SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews, Fife KY16 9SS, UK
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21
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Kushwaha P, Sunko V, Moll PJW, Bawden L, Riley JM, Nandi N, Rosner H, Schmidt MP, Arnold F, Hassinger E, Kim TK, Hoesch M, Mackenzie AP, King PDC. Nearly free electrons in a 5d delafossite oxide metal. Sci Adv 2015; 1:e1500692. [PMID: 26601308 PMCID: PMC4646822 DOI: 10.1126/sciadv.1500692] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/28/2015] [Accepted: 08/20/2015] [Indexed: 05/23/2023]
Abstract
Understanding the role of electron correlations in strong spin-orbit transition-metal oxides is key to the realization of numerous exotic phases including spin-orbit-assisted Mott insulators, correlated topological solids, and prospective new high-temperature superconductors. To date, most attention has been focused on the 5d iridium-based oxides. We instead consider the Pt-based delafossite oxide PtCoO2. Our transport measurements, performed on single-crystal samples etched to well-defined geometries using focused ion beam techniques, yield a room temperature resistivity of only 2.1 microhm·cm (μΩ-cm), establishing PtCoO2 as the most conductive oxide known. From angle-resolved photoemission and density functional theory, we show that the underlying Fermi surface is a single cylinder of nearly hexagonal cross-section, with very weak dispersion along k z . Despite being predominantly composed of d-orbital character, the conduction band is remarkably steep, with an average effective mass of only 1.14m e. Moreover, the sharp spectral features observed in photoemission remain well defined with little additional broadening for more than 500 meV below E F, pointing to suppressed electron-electron scattering. Together, our findings establish PtCoO2 as a model nearly-free-electron system in a 5d delafossite transition-metal oxide.
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Affiliation(s)
- Pallavi Kushwaha
- Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, 01187 Dresden, Germany
| | - Veronika Sunko
- Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, 01187 Dresden, Germany
- Scottish Universities Physics Alliance, School of Physics and Astronomy, University of St. Andrews, St. Andrews, Fife KY16 9SS, UK
| | - Philip J. W. Moll
- Laboratory for Solid State Physics, ETH Zurich, CH-8093 Zurich, Switzerland
| | - Lewis Bawden
- Scottish Universities Physics Alliance, School of Physics and Astronomy, University of St. Andrews, St. Andrews, Fife KY16 9SS, UK
| | - Jonathon M. Riley
- Scottish Universities Physics Alliance, School of Physics and Astronomy, University of St. Andrews, St. Andrews, Fife KY16 9SS, UK
- Diamond Light Source, Harwell Campus, Didcot, Oxfordshire OX11 0DE, UK
| | - Nabhanila Nandi
- Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, 01187 Dresden, Germany
| | - Helge Rosner
- Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, 01187 Dresden, Germany
| | - Marcus P. Schmidt
- Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, 01187 Dresden, Germany
| | - Frank Arnold
- Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, 01187 Dresden, Germany
| | - Elena Hassinger
- Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, 01187 Dresden, Germany
| | - Timur K. Kim
- Diamond Light Source, Harwell Campus, Didcot, Oxfordshire OX11 0DE, UK
| | - Moritz Hoesch
- Diamond Light Source, Harwell Campus, Didcot, Oxfordshire OX11 0DE, UK
| | - Andrew P. Mackenzie
- Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, 01187 Dresden, Germany
- Scottish Universities Physics Alliance, School of Physics and Astronomy, University of St. Andrews, St. Andrews, Fife KY16 9SS, UK
| | - Phil D. C. King
- Scottish Universities Physics Alliance, School of Physics and Astronomy, University of St. Andrews, St. Andrews, Fife KY16 9SS, UK
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22
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Grubišić Čabo A, Miwa JA, Grønborg SS, Riley JM, Johannsen JC, Cacho C, Alexander O, Chapman RT, Springate E, Grioni M, Lauritsen JV, King PDC, Hofmann P, Ulstrup S. Observation of Ultrafast Free Carrier Dynamics in Single Layer MoS2. Nano Lett 2015; 15:5883-7. [PMID: 26315566 DOI: 10.1021/acs.nanolett.5b01967] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
The dynamics of excited electrons and holes in single layer (SL) MoS2 have so far been difficult to disentangle from the excitons that dominate the optical response of this material. Here, we use time- and angle-resolved photoemission spectroscopy for a SL of MoS2 on a metallic substrate to directly measure the excited free carriers. This allows us to ascertain a direct quasiparticle band gap of 1.95 eV and determine an ultrafast (50 fs) extraction of excited free carriers via the metal in contact with the SL MoS2. This process is of key importance for optoelectronic applications that rely on separated free carriers rather than excitons.
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Affiliation(s)
- Antonija Grubišić Čabo
- Department of Physics and Astronomy, Interdisciplinary Nanoscience Center, Aarhus University , 8000 Aarhus C, Denmark
| | - Jill A Miwa
- Department of Physics and Astronomy, Interdisciplinary Nanoscience Center, Aarhus University , 8000 Aarhus C, Denmark
| | - Signe S Grønborg
- Department of Physics and Astronomy, Interdisciplinary Nanoscience Center, Aarhus University , 8000 Aarhus C, Denmark
| | - Jonathon M Riley
- SUPA, School of Physics and Astronomy, University of St. Andrews , St. Andrews, Fife KY16 9SS, United Kingdom
| | - Jens C Johannsen
- Institute of Condensed Matter Physics, École Polytechnique Fédérale de Lausanne (EPFL) , 1015 Lausanne, Switzerland
| | - Cephise Cacho
- Central Laser Facility, STFC Rutherford Appleton Laboratory, Harwell, Didcot OX11 0QX, United Kingdom
| | - Oliver Alexander
- Central Laser Facility, STFC Rutherford Appleton Laboratory, Harwell, Didcot OX11 0QX, United Kingdom
| | - Richard T Chapman
- Central Laser Facility, STFC Rutherford Appleton Laboratory, Harwell, Didcot OX11 0QX, United Kingdom
| | - Emma Springate
- Central Laser Facility, STFC Rutherford Appleton Laboratory, Harwell, Didcot OX11 0QX, United Kingdom
| | - Marco Grioni
- Institute of Condensed Matter Physics, École Polytechnique Fédérale de Lausanne (EPFL) , 1015 Lausanne, Switzerland
| | - Jeppe V Lauritsen
- Department of Physics and Astronomy, Interdisciplinary Nanoscience Center, Aarhus University , 8000 Aarhus C, Denmark
| | - Phil D C King
- SUPA, School of Physics and Astronomy, University of St. Andrews , St. Andrews, Fife KY16 9SS, United Kingdom
| | - Philip Hofmann
- Department of Physics and Astronomy, Interdisciplinary Nanoscience Center, Aarhus University , 8000 Aarhus C, Denmark
| | - Søren Ulstrup
- Department of Physics and Astronomy, Interdisciplinary Nanoscience Center, Aarhus University , 8000 Aarhus C, Denmark
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23
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Bawden L, Riley JM, Kim CH, Sankar R, Monkman EJ, Shai DE, Wei HI, Lochocki EB, Wells JW, Meevasana W, Kim TK, Hoesch M, Ohtsubo Y, Le Fèvre P, Fennie CJ, Shen KM, Chou F, King PDC. Hierarchical spin-orbital polarization of a giant Rashba system. Sci Adv 2015; 1:e1500495. [PMID: 26601268 PMCID: PMC4643772 DOI: 10.1126/sciadv.1500495] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/20/2015] [Accepted: 06/16/2015] [Indexed: 06/02/2023]
Abstract
The Rashba effect is one of the most striking manifestations of spin-orbit coupling in solids and provides a cornerstone for the burgeoning field of semiconductor spintronics. It is typically assumed to manifest as a momentum-dependent splitting of a single initially spin-degenerate band into two branches with opposite spin polarization. Combining polarization-dependent and resonant angle-resolved photoemission measurements with density functional theory calculations, we show that the two "spin-split" branches of the model giant Rashba system BiTeI additionally develop disparate orbital textures, each of which is coupled to a distinct spin configuration. This necessitates a reinterpretation of spin splitting in Rashba-like systems and opens new possibilities for controlling spin polarization through the orbital sector.
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Affiliation(s)
- Lewis Bawden
- SUPA, School of Physics and Astronomy, University of St. Andrews, St. Andrews, Fife KY16 9SS, UK
| | - Jonathan M. Riley
- SUPA, School of Physics and Astronomy, University of St. Andrews, St. Andrews, Fife KY16 9SS, UK
- Diamond Light Source, Harwell Campus, Didcot OX11 0DE, UK
| | - Choong H. Kim
- School of Applied & Engineering Physics, Cornell University, Ithaca, NY 14853, USA
| | - Raman Sankar
- Center for Condensed Matter Sciences, National Taiwan University, Taipei 10617, Taiwan
- Institute of Physics, Academia Sinica, Taipei 11529, Taiwan
| | - Eric J. Monkman
- Laboratory of Atomic and Solid State Physics, Department of Physics, Cornell University, Ithaca, NY 14853, USA
| | - Daniel E. Shai
- Laboratory of Atomic and Solid State Physics, Department of Physics, Cornell University, Ithaca, NY 14853, USA
| | - Haofei I. Wei
- Laboratory of Atomic and Solid State Physics, Department of Physics, Cornell University, Ithaca, NY 14853, USA
| | - Edward B. Lochocki
- Laboratory of Atomic and Solid State Physics, Department of Physics, Cornell University, Ithaca, NY 14853, USA
| | - Justin W. Wells
- Department of Physics, Norwegian University of Science and Technology (NTNU), N-7491 Trondheim, Norway
| | - Worawat Meevasana
- School of Physics, Suranaree University of Technology, Nakhon Ratchasima 30000, Thailand
- NANOTEC-SUT Center of Excellence on Advanced Functional Nanomaterials, Suranaree University of Technology, Nakhon Ratchasima 30000, Thailand
| | - Timur K. Kim
- Diamond Light Source, Harwell Campus, Didcot OX11 0DE, UK
| | - Moritz Hoesch
- Diamond Light Source, Harwell Campus, Didcot OX11 0DE, UK
| | - Yoshiyuki Ohtsubo
- Synchrotron SOLEIL, CNRS-CEA, L’Orme des Merisiers, Saint-Aubin-BP48, 91192 Gif-sur-Yvette, France
| | - Patrick Le Fèvre
- Synchrotron SOLEIL, CNRS-CEA, L’Orme des Merisiers, Saint-Aubin-BP48, 91192 Gif-sur-Yvette, France
| | - Craig J. Fennie
- School of Applied & Engineering Physics, Cornell University, Ithaca, NY 14853, USA
| | - Kyle M. Shen
- Laboratory of Atomic and Solid State Physics, Department of Physics, Cornell University, Ithaca, NY 14853, USA
- Kavli Institute at Cornell for Nanoscale Science, Ithaca, NY 14853, USA
| | - Fangcheng Chou
- Center for Condensed Matter Sciences, National Taiwan University, Taipei 10617, Taiwan
| | - Phil D. C. King
- SUPA, School of Physics and Astronomy, University of St. Andrews, St. Andrews, Fife KY16 9SS, UK
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24
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Nie YF, Di Sante D, Chatterjee S, King PDC, Uchida M, Ciuchi S, Schlom DG, Shen KM. Formation and Observation of a Quasi-Two-Dimensional dxy Electron Liquid in Epitaxially Stabilized Sr(2-x)La(x)TiO4 Thin Films. Phys Rev Lett 2015; 115:096405. [PMID: 26371669 DOI: 10.1103/physrevlett.115.096405] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/20/2014] [Indexed: 06/05/2023]
Abstract
We report the formation and observation of an electron liquid in Sr(2-x)La(x)TiO4, the quasi-two-dimensional counterpart of SrTiO3, through reactive molecular-beam epitaxy and in situ angle-resolved photoemission spectroscopy. The lowest lying states are found to be comprised of Ti 3d_{xy} orbitals, analogous to the LaAlO3/SrTiO3 interface and exhibit unusually broad features characterized by quantized energy levels and a reduced Luttinger volume. Using model calculations, we explain these characteristics through an interplay of disorder and electron-phonon coupling acting cooperatively at similar energy scales, which provides a possible mechanism for explaining the low free carrier concentrations observed at various oxide heterostructures such as the LaAlO3/SrTiO3 interface.
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Affiliation(s)
- Y F Nie
- National Laboratory of Solid State Microstructures and College of Engineering and Applied Sciences, Nanjing University, Nanjing 210093, People's Republic of China
- Laboratory of Atomic and Solid State Physics, Department of Physics, Cornell University, Ithaca, New York 14853, USA
- Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14853, USA
| | - D Di Sante
- Department of Physical and Chemical Sciences, University of L'Aquila, via Vetoio, Coppito, L'Aquila I-67100, Italy
- CNR-SPIN, Via Vetoio, L'Aquila I-67100, Italy
| | - S Chatterjee
- Laboratory of Atomic and Solid State Physics, Department of Physics, Cornell University, Ithaca, New York 14853, USA
| | - P D C King
- Laboratory of Atomic and Solid State Physics, Department of Physics, Cornell University, Ithaca, New York 14853, USA
- Kavli Institute at Cornell for Nanoscale Science, Ithaca, New York 14853, USA
| | - M Uchida
- Laboratory of Atomic and Solid State Physics, Department of Physics, Cornell University, Ithaca, New York 14853, USA
| | - S Ciuchi
- Department of Physical and Chemical Sciences, University of L'Aquila, via Vetoio, Coppito, L'Aquila I-67100, Italy
- CNR-ISC, Via dei Taurini, Rome I-00185, Italy
| | - D G Schlom
- Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14853, USA
- Kavli Institute at Cornell for Nanoscale Science, Ithaca, New York 14853, USA
| | - K M Shen
- Laboratory of Atomic and Solid State Physics, Department of Physics, Cornell University, Ithaca, New York 14853, USA
- Kavli Institute at Cornell for Nanoscale Science, Ithaca, New York 14853, USA
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25
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Walker SM, Bruno FY, Wang Z, de la Torre A, Riccó S, Tamai A, Kim TK, Hoesch M, Shi M, Bahramy MS, King PDC, Baumberger F. Carrier-Density Control of the SrTiO3 (001) Surface 2D Electron Gas studied by ARPES. Adv Mater 2015; 27:3894-3899. [PMID: 26010071 DOI: 10.1002/adma.201501556] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/01/2015] [Revised: 04/29/2015] [Indexed: 06/04/2023]
Abstract
The origin of the 2D electron gas (2DEG)stabilized at the bare surface of SrTiO3 (001) is investigated. Using high-resolution angle-resolved photoemission and core-level spectroscopy, it is shown conclusively that this 2DEG arises from light-induced oxygen vacancies. The dominant mechanism driving vacancy formation is identified, allowing unprecedented control over the 2DEG carrier density.
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Affiliation(s)
- Siobhan McKeown Walker
- Department of Quantum Matter Physics, University of Geneva, 24 Quai Ernest-Ansermet, 1211, Geneva, Switzerland
| | - Flavio Yair Bruno
- Department of Quantum Matter Physics, University of Geneva, 24 Quai Ernest-Ansermet, 1211, Geneva, Switzerland
| | - Zhiming Wang
- Swiss Light Source, Paul Scherrer Institute, 5232, Villigen, Switzerland
| | - Alberto de la Torre
- Department of Quantum Matter Physics, University of Geneva, 24 Quai Ernest-Ansermet, 1211, Geneva, Switzerland
| | - Sara Riccó
- Department of Quantum Matter Physics, University of Geneva, 24 Quai Ernest-Ansermet, 1211, Geneva, Switzerland
| | - Anna Tamai
- Department of Quantum Matter Physics, University of Geneva, 24 Quai Ernest-Ansermet, 1211, Geneva, Switzerland
| | - Timur K Kim
- Diamond Light Source, Harwell Campus, Didcot, OX11 0DE, UK
| | - Moritz Hoesch
- Diamond Light Source, Harwell Campus, Didcot, OX11 0DE, UK
| | - Ming Shi
- Swiss Light Source, Paul Scherrer Institute, 5232, Villigen, Switzerland
| | - Mohammad Saeed Bahramy
- Quantum-Phase Electronics Center, Department of Applied Physics, University of Tokyo, 113-8656, Tokyo, Japan
- RIKEN Center for Emergent Matter Science, 351-0198, Wako, Japan
| | - Phil D C King
- SUPA School of Physics and Astronomy, University of St Andrews, KY16 9SS, St Andrews, UK
| | - Felix Baumberger
- Department of Quantum Matter Physics, University of Geneva, 24 Quai Ernest-Ansermet, 1211, Geneva, Switzerland
- Swiss Light Source, Paul Scherrer Institute, 5232, Villigen, Switzerland
- SUPA School of Physics and Astronomy, University of St Andrews, KY16 9SS, St Andrews, UK
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26
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Johannsen JC, Ulstrup S, Crepaldi A, Cilento F, Zacchigna M, Miwa JA, Cacho C, Chapman RT, Springate E, Fromm F, Raidel C, Seyller T, King PDC, Parmigiani F, Grioni M, Hofmann P. Tunable carrier multiplication and cooling in graphene. Nano Lett 2015; 15:326-331. [PMID: 25458168 DOI: 10.1021/nl503614v] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Time- and angle-resolved photoemission measurements on two doped graphene samples displaying different doping levels reveal remarkable differences in the ultrafast dynamics of the hot carriers in the Dirac cone. In the more strongly (n-)doped graphene, we observe larger carrier multiplication factors (>3) and a significantly faster phonon-mediated cooling of the carriers back to equilibrium compared to in the less (p-)doped graphene. These results suggest that a careful tuning of the doping level allows for an effective manipulation of graphene's dynamical response to a photoexcitation.
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Affiliation(s)
- Jens Christian Johannsen
- Institute of Condensed Matter Physics, École Polytechnique Fédérale de Lausanne (EPFL) , 1015 Lausanne, Switzerland
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27
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Nie YF, King PDC, Kim CH, Uchida M, Wei HI, Faeth BD, Ruf JP, Ruff JPC, Xie L, Pan X, Fennie CJ, Schlom DG, Shen KM. Interplay of spin-orbit interactions, dimensionality, and octahedral rotations in semimetallic SrIrO(3). Phys Rev Lett 2015; 114:016401. [PMID: 25615483 DOI: 10.1103/physrevlett.114.016401] [Citation(s) in RCA: 59] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/12/2014] [Indexed: 06/04/2023]
Abstract
We employ reactive molecular-beam epitaxy to synthesize the metastable perovskite SrIrO(3) and utilize in situ angle-resolved photoemission to reveal its electronic structure as an exotic narrow-band semimetal. We discover remarkably narrow bands which originate from a confluence of strong spin-orbit interactions, dimensionality, and both in- and out-of-plane IrO(6) octahedral rotations. The partial occupation of numerous bands with strongly mixed orbital characters signals the breakdown of the single-band Mott picture that characterizes its insulating two-dimensional counterpart, Sr(2)IrO(4), illustrating the power of structure-property relations for manipulating the subtle balance between spin-orbit interactions and electron-electron interactions.
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Affiliation(s)
- Y F Nie
- Department of Physics, Laboratory of Atomic and Solid State Physics, Cornell University, Ithaca, New York 14853, USA and Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14853, USA and National Laboratory of Solid State Microstructures and College of Engineering and Applied Sciences, Nanjing University, Nanjing 210093, People's Republic of China
| | - P D C King
- Department of Physics, Laboratory of Atomic and Solid State Physics, Cornell University, Ithaca, New York 14853, USA and Kavli Institute at Cornell for Nanoscale Science, Ithaca, New York 14853, USA
| | - C H Kim
- Department of Applied and Engineering Physics, Cornell University, Ithaca, New York 14853, USA
| | - M Uchida
- Department of Physics, Laboratory of Atomic and Solid State Physics, Cornell University, Ithaca, New York 14853, USA
| | - H I Wei
- Department of Physics, Laboratory of Atomic and Solid State Physics, Cornell University, Ithaca, New York 14853, USA
| | - B D Faeth
- Department of Physics, Laboratory of Atomic and Solid State Physics, Cornell University, Ithaca, New York 14853, USA
| | - J P Ruf
- Department of Physics, Laboratory of Atomic and Solid State Physics, Cornell University, Ithaca, New York 14853, USA
| | - J P C Ruff
- CHESS, Cornell University, Ithaca, New York 14853, USA
| | - L Xie
- National Laboratory of Solid State Microstructures and College of Engineering and Applied Sciences, Nanjing University, Nanjing 210093, People's Republic of China and Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109, USA
| | - X Pan
- Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109, USA
| | - C J Fennie
- Department of Applied and Engineering Physics, Cornell University, Ithaca, New York 14853, USA
| | - D G Schlom
- Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14853, USA and Kavli Institute at Cornell for Nanoscale Science, Ithaca, New York 14853, USA
| | - K M Shen
- Department of Physics, Laboratory of Atomic and Solid State Physics, Cornell University, Ithaca, New York 14853, USA and Kavli Institute at Cornell for Nanoscale Science, Ithaca, New York 14853, USA
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28
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Walker SM, de la Torre A, Bruno FY, Tamai A, Kim TK, Hoesch M, Shi M, Bahramy MS, King PDC, Baumberger F. Control of a two-dimensional electron gas on SrTiO₃(111) by atomic oxygen. Phys Rev Lett 2014; 113:177601. [PMID: 25379937 DOI: 10.1103/physrevlett.113.177601] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/12/2014] [Indexed: 06/04/2023]
Abstract
We report on the formation of a two-dimensional electron gas (2DEG) at the bare surface of (111) oriented SrTiO3. Angle resolved photoemission experiments reveal highly itinerant carriers with a sixfold symmetric Fermi surface and strongly anisotropic effective masses. The electronic structure of the 2DEG is in good agreement with self-consistent tight-binding supercell calculations that incorporate a confinement potential due to surface band bending. We further demonstrate that alternate exposure of the surface to ultraviolet light and atomic oxygen allows tuning of the carrier density and the complete suppression of the 2DEG.
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Affiliation(s)
- S McKeown Walker
- Département de Physique de la Matière Condensée, Universitée de Genève, 24 Quai Ernest-Ansermet, 1211 Genève 4, Switzerland
| | - A de la Torre
- Département de Physique de la Matière Condensée, Universitée de Genève, 24 Quai Ernest-Ansermet, 1211 Genève 4, Switzerland
| | - F Y Bruno
- Département de Physique de la Matière Condensée, Universitée de Genève, 24 Quai Ernest-Ansermet, 1211 Genève 4, Switzerland
| | - A Tamai
- Département de Physique de la Matière Condensée, Universitée de Genève, 24 Quai Ernest-Ansermet, 1211 Genève 4, Switzerland
| | - T K Kim
- Diamond Light Source, Harwell Campus, Didcot OX11 0DE, United Kingdom
| | - M Hoesch
- Diamond Light Source, Harwell Campus, Didcot OX11 0DE, United Kingdom
| | - M Shi
- Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
| | - M S Bahramy
- Quantum-Phase Electronics Center, Department of Applied Physics, The University of Tokyo, Tokyo 113-8656, Japan and RIKEN Center for Emergent Matter Science (CEMS), Wako 351-0198, Japan
| | - P D C King
- SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews, Fife KY16 9SS, United Kingdom
| | - F Baumberger
- Département de Physique de la Matière Condensée, Universitée de Genève, 24 Quai Ernest-Ansermet, 1211 Genève 4, Switzerland and Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland and SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews, Fife KY16 9SS, United Kingdom
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29
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Ulstrup S, Johannsen JC, Cilento F, Miwa JA, Crepaldi A, Zacchigna M, Cacho C, Chapman R, Springate E, Mammadov S, Fromm F, Raidel C, Seyller T, Parmigiani F, Grioni M, King PDC, Hofmann P. Ultrafast dynamics of massive dirac fermions in bilayer graphene. Phys Rev Lett 2014; 112:257401. [PMID: 25014829 DOI: 10.1103/physrevlett.112.257401] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/01/2014] [Indexed: 06/03/2023]
Abstract
Bilayer graphene is a highly promising material for electronic and optoelectronic applications since it is supporting massive Dirac fermions with a tunable band gap. However, no consistent picture of the gap's effect on the optical and transport behavior has emerged so far, and it has been proposed that the insulating nature of the gap could be compromised by unavoidable structural defects, by topological in-gap states, or that the electronic structure could be altogether changed by many-body effects. Here, we directly follow the excited carriers in bilayer graphene on a femtosecond time scale, using ultrafast time- and angle-resolved photoemission. We find a behavior consistent with a single-particle band gap. Compared to monolayer graphene, the existence of this band gap leads to an increased carrier lifetime in the minimum of the lowest conduction band. This is in sharp contrast to the second substate of the conduction band, in which the excited electrons decay through fast, phonon-assisted interband transitions.
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Affiliation(s)
- Søren Ulstrup
- Department of Physics and Astronomy, Interdisciplinary Nanoscience Center (iNANO), Aarhus University, 8000 Aarhus C, Denmark
| | - Jens Christian Johannsen
- Institute of Condensed Matter Physics, École Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
| | | | - Jill A Miwa
- Department of Physics and Astronomy, Interdisciplinary Nanoscience Center (iNANO), Aarhus University, 8000 Aarhus C, Denmark
| | | | | | - Cephise Cacho
- Central Laser Facility, STFC Rutherford Appleton Laboratory, Didcot OX11 0QX, United Kingdom
| | - Richard Chapman
- Central Laser Facility, STFC Rutherford Appleton Laboratory, Didcot OX11 0QX, United Kingdom
| | - Emma Springate
- Central Laser Facility, STFC Rutherford Appleton Laboratory, Didcot OX11 0QX, United Kingdom
| | - Samir Mammadov
- Institut für Physik, Technische Universität Chemnitz, 09126 Chemnitz, Germany
| | - Felix Fromm
- Institut für Physik, Technische Universität Chemnitz, 09126 Chemnitz, Germany
| | - Christian Raidel
- Institut für Physik, Technische Universität Chemnitz, 09126 Chemnitz, Germany
| | - Thomas Seyller
- Institut für Physik, Technische Universität Chemnitz, 09126 Chemnitz, Germany
| | - Fulvio Parmigiani
- Sincrotrone Trieste, 34149 Trieste, Italy and Department of Physics, University of Trieste, 34127 Trieste, Italy
| | - Marco Grioni
- Institute of Condensed Matter Physics, École Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
| | - Phil D C King
- SUPA, School of Physics and Astronomy, University of St. Andrews, St. Andrews, Fife KY16 9SS, United Kingdom
| | - Philip Hofmann
- Department of Physics and Astronomy, Interdisciplinary Nanoscience Center (iNANO), Aarhus University, 8000 Aarhus C, Denmark
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30
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King PDC, Wei HI, Nie YF, Uchida M, Adamo C, Zhu S, He X, Božović I, Schlom DG, Shen KM. Atomic-scale control of competing electronic phases in ultrathin LaNiO₃. Nat Nanotechnol 2014; 9:443-7. [PMID: 24705511 DOI: 10.1038/nnano.2014.59] [Citation(s) in RCA: 64] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/29/2013] [Accepted: 02/21/2014] [Indexed: 05/27/2023]
Abstract
In an effort to scale down electronic devices to atomic dimensions, the use of transition-metal oxides may provide advantages over conventional semiconductors. Their high carrier densities and short electronic length scales are desirable for miniaturization, while strong interactions that mediate exotic phase diagrams open new avenues for engineering emergent properties. Nevertheless, understanding how their correlated electronic states can be manipulated at the nanoscale remains challenging. Here, we use angle-resolved photoemission spectroscopy to uncover an abrupt destruction of Fermi liquid-like quasiparticles in the correlated metal LaNiO₃ when confined to a critical film thickness of two unit cells. This is accompanied by the onset of an insulating phase as measured by electrical transport. We show how this is driven by an instability to an incipient order of the underlying quantum many-body system, demonstrating the power of artificial confinement to harness control over competing phases in complex oxides with atomic-scale precision.
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Affiliation(s)
- P D C King
- 1] Kavli Institute at Cornell for Nanoscale Science, Ithaca, New York 14853, USA [2] Laboratory of Atomic and Solid State Physics, Department of Physics, Cornell University, Ithaca, New York 14853, USA
| | - H I Wei
- Laboratory of Atomic and Solid State Physics, Department of Physics, Cornell University, Ithaca, New York 14853, USA
| | - Y F Nie
- 1] Laboratory of Atomic and Solid State Physics, Department of Physics, Cornell University, Ithaca, New York 14853, USA [2] Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14853, USA
| | - M Uchida
- Laboratory of Atomic and Solid State Physics, Department of Physics, Cornell University, Ithaca, New York 14853, USA
| | - C Adamo
- Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14853, USA
| | - S Zhu
- Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14853, USA
| | - X He
- Brookhaven National Laboratory, Upton, New York 11973-5000, USA
| | - I Božović
- Brookhaven National Laboratory, Upton, New York 11973-5000, USA
| | - D G Schlom
- 1] Kavli Institute at Cornell for Nanoscale Science, Ithaca, New York 14853, USA [2] Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14853, USA
| | - K M Shen
- 1] Kavli Institute at Cornell for Nanoscale Science, Ithaca, New York 14853, USA [2] Laboratory of Atomic and Solid State Physics, Department of Physics, Cornell University, Ithaca, New York 14853, USA
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31
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Eknapakul T, King PDC, Asakawa M, Buaphet P, He RH, Mo SK, Takagi H, Shen KM, Baumberger F, Sasagawa T, Jungthawan S, Meevasana W. Electronic structure of a quasi-freestanding MoS₂ monolayer. Nano Lett 2014; 14:1312-6. [PMID: 24552197 DOI: 10.1021/nl4042824] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Several transition-metal dichalcogenides exhibit a striking crossover from indirect to direct band gap semiconductors as they are thinned down to a single monolayer. Here, we demonstrate how an electronic structure characteristic of the isolated monolayer can be created at the surface of a bulk MoS2 crystal. This is achieved by intercalating potassium in the interlayer van der Waals gap, expanding its size while simultaneously doping electrons into the conduction band. Our angle-resolved photoemission measurements reveal resulting electron pockets centered at the K̅ and K' points of the Brillouin zone, providing the first momentum-resolved measurements of how the conduction band dispersions evolve to yield an approximately direct band gap of ∼1.8 eV in quasi-freestanding monolayer MoS2. As well as validating previous theoretical proposals, this establishes a novel methodology for manipulating electronic structure in transition-metal dichalcogenides, opening a new route for the generation of large-area quasi-freestanding monolayers for future fundamental study and use in practical applications.
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Affiliation(s)
- T Eknapakul
- School of Physics, Suranaree University of Technology , Nakhon Ratchasima, 30000, Thailand
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32
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Arpino KE, Wallace DC, Nie YF, Birol T, King PDC, Chatterjee S, Uchida M, Koohpayeh SM, Wen JJ, Page K, Fennie CJ, Shen KM, McQueen TM. Evidence for topologically protected surface states and a superconducting phase in [Tl4](Tl(1-x)Sn(x))Te3 using photoemission, specific heat, and magnetization measurements, and density functional theory. Phys Rev Lett 2014; 112:017002. [PMID: 24483920 DOI: 10.1103/physrevlett.112.017002] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/19/2013] [Indexed: 05/22/2023]
Abstract
We report the discovery of surface states in the perovskite superconductor [Tl4]TlTe3 (Tl5Te3) and its nonsuperconducting tin-doped derivative [Tl4](Tl0.4Sn0.6)Te3 as observed by angle-resolved photoemission spectroscopy. Density functional theory calculations predict that the surface states are protected by a Z2 topology of the bulk band structure. Specific heat and magnetization measurements show that Tl5Te3 has a superconducting volume fraction in excess of 95%. Thus Tl5Te3 is an ideal material in which to study the interplay of bulk band topology and superconductivity.
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Affiliation(s)
- K E Arpino
- Department of Chemistry, The Johns Hopkins University, Baltimore, Maryland 21218, USA and Institute for Quantum Matter, Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, Maryland 21218, USA
| | - D C Wallace
- Department of Chemistry, The Johns Hopkins University, Baltimore, Maryland 21218, USA and Institute for Quantum Matter, Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, Maryland 21218, USA
| | - Y F Nie
- Department of Physics, Laboratory of Atomic and Solid State Physics, Cornell University, Ithaca, New York 14853, USA and Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14853, USA
| | - T Birol
- School of Applied and Engineering Physics, Cornell University, Ithaca, New York 14853, USA
| | - P D C King
- Department of Physics, Laboratory of Atomic and Solid State Physics, Cornell University, Ithaca, New York 14853, USA and Kavli Institute at Cornell for Nanoscale Science, Cornell University, Ithaca, New York 14853, USA
| | - S Chatterjee
- Department of Physics, Laboratory of Atomic and Solid State Physics, Cornell University, Ithaca, New York 14853, USA
| | - M Uchida
- Department of Physics, Laboratory of Atomic and Solid State Physics, Cornell University, Ithaca, New York 14853, USA
| | - S M Koohpayeh
- Institute for Quantum Matter, Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, Maryland 21218, USA
| | - J-J Wen
- Institute for Quantum Matter, Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, Maryland 21218, USA
| | - K Page
- Lujan Neutron Scattering Center, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - C J Fennie
- School of Applied and Engineering Physics, Cornell University, Ithaca, New York 14853, USA
| | - K M Shen
- Department of Physics, Laboratory of Atomic and Solid State Physics, Cornell University, Ithaca, New York 14853, USA and Kavli Institute at Cornell for Nanoscale Science, Cornell University, Ithaca, New York 14853, USA
| | - T M McQueen
- Department of Chemistry, The Johns Hopkins University, Baltimore, Maryland 21218, USA and Institute for Quantum Matter, Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, Maryland 21218, USA
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33
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Zhang KHL, Egdell RG, Offi F, Iacobucci S, Petaccia L, Gorovikov S, King PDC. Microscopic origin of electron accumulation in In2O3. Phys Rev Lett 2013; 110:056803. [PMID: 23414041 DOI: 10.1103/physrevlett.110.056803] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/30/2012] [Indexed: 06/01/2023]
Abstract
Angle-resolved photoemission spectroscopy reveals the presence of a two-dimensional electron gas at the surface of In(2)O(3)(111). Quantized subband states arise within a confining potential well associated with surface electron accumulation. Coupled Poisson-Schrödinger calculations suggest that downward band bending for the conduction band must be much bigger than band bending in the valence band. Surface oxygen vacancies acting as doubly ionized shallow donors are shown to provide the free electrons within this accumulation layer. Identification of the origin of electron accumulation in transparent conducting oxides has significant implications in the realization of devices based on these compounds.
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Affiliation(s)
- K H L Zhang
- Department of Chemistry, University of Oxford, Inorganic Chemistry Laboratory, South Parks Road, Oxford OX1 3QR, United Kingdom
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34
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Scanlon DO, King PDC, Singh RP, de la Torre A, Walker SM, Balakrishnan G, Baumberger F, Catlow CRA. Controlling bulk conductivity in topological insulators: key role of anti-site defects. Adv Mater 2012; 24:2154-8. [PMID: 22430985 DOI: 10.1002/adma.201200187] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Intrinsic topological insulators are realized by alloying Bi(2)Te(3) with Bi(2)Se(3). Angle-resolved photoemission and bulk transport measurements reveal that the Fermi level is readily tuned into the bulk bandgap. First-principles calculations of the native defect landscape highlight the key role of anti-site defects for achieving this, and predict optimal growth conditions to realize maximally resistive topological insulators.
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Affiliation(s)
- D O Scanlon
- University College London, Kathleen Lonsdale Materials Chemistry, Department of Chemistry, London, UK.
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35
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King PDC, He RH, Eknapakul T, Buaphet P, Mo SK, Kaneko Y, Harashima S, Hikita Y, Bahramy MS, Bell C, Hussain Z, Tokura Y, Shen ZX, Hwang HY, Baumberger F, Meevasana W. Subband structure of a two-dimensional electron gas formed at the polar surface of the strong spin-orbit perovskite KTaO3. Phys Rev Lett 2012; 108:117602. [PMID: 22540511 DOI: 10.1103/physrevlett.108.117602] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/31/2011] [Indexed: 05/31/2023]
Abstract
We demonstrate the formation of a two-dimensional electron gas (2DEG) at the (100) surface of the 5d transition-metal oxide KTaO3. From angle-resolved photoemission, we find that quantum confinement lifts the orbital degeneracy of the bulk band structure and leads to a 2DEG composed of ladders of subband states of both light and heavy carriers. Despite the strong spin-orbit coupling, our measurements provide a direct upper bound for the potential Rashba spin splitting of only Δk(parallel)}~0.02 Å(-1) at the Fermi level. The polar nature of the KTaO3(100) surface appears to help mediate the formation of the 2DEG as compared to nonpolar SrTiO3(100).
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Affiliation(s)
- P D C King
- SUPA, School of Physics and Astronomy, University of St. Andrews, St. Andrews, Fife, United Kingdom
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36
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King PDC, Hatch RC, Bianchi M, Ovsyannikov R, Lupulescu C, Landolt G, Slomski B, Dil JH, Guan D, Mi JL, Rienks EDL, Fink J, Lindblad A, Svensson S, Bao S, Balakrishnan G, Iversen BB, Osterwalder J, Eberhardt W, Baumberger F, Hofmann P. Large tunable Rashba spin splitting of a two-dimensional electron gas in Bi2Se3. Phys Rev Lett 2011; 107:096802. [PMID: 21929260 DOI: 10.1103/physrevlett.107.096802] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/24/2011] [Indexed: 05/13/2023]
Abstract
We report a Rashba spin splitting of a two-dimensional electron gas in the topological insulator Bi(2)Se(3) from angle-resolved photoemission spectroscopy. We further demonstrate its electrostatic control, and show that spin splittings can be achieved which are at least an order-of-magnitude larger than in other semiconductors. Together these results show promise for the miniaturization of spintronic devices to the nanoscale and their operation at room temperature.
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Affiliation(s)
- P D C King
- School of Physics and Astronomy, University of St. Andrews, St. Andrews, Fife KY16 9SS, United Kingdom
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37
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Abstract
Despite an extensive research effort for over 60 years, an understanding of the origins of conductivity in wide band gap transparent conducting oxide (TCO) semiconductors remains elusive. While TCOs have already found widespread use in device applications requiring a transparent contact, there are currently enormous efforts to (i) increase the conductivity of existing materials, (ii) identify suitable alternatives, and (iii) attempt to gain semiconductor-engineering levels of control over their carrier density, essential for the incorporation of TCOs into a new generation of multifunctional transparent electronic devices. These efforts, however, are dependent on a microscopic identification of the defects and impurities leading to the high unintentional carrier densities present in these materials. Here, we review recent developments towards such an understanding. While oxygen vacancies are commonly assumed to be the source of the conductivity, there is increasing evidence that this is not a sufficient mechanism to explain the total measured carrier concentrations. In fact, many studies suggest that oxygen vacancies are deep, rather than shallow, donors, and their abundance in as-grown material is also debated. We discuss other potential contributions to the conductivity in TCOs, including other native defects, their complexes, and in particular hydrogen impurities. Convincing theoretical and experimental evidence is presented for the donor nature of hydrogen across a range of TCO materials, and while its stability and the role of interstitial versus substitutional species are still somewhat open questions, it is one of the leading contenders for yielding unintentional conductivity in TCOs. We also review recent work indicating that the surfaces of TCOs can support very high carrier densities, opposite to the case for conventional semiconductors. In thin-film materials/devices and, in particular, nanostructures, the surface can have a large impact on the total conductivity in TCOs. We discuss models that attempt to explain both the bulk and surface conductivity on the basis of bulk band structure features common across the TCOs, and compare these materials to other semiconductors. Finally, we briefly consider transparency in these materials, and its interplay with conductivity. Understanding this interplay, as well as the microscopic contenders for providing the conductivity of these materials, will prove essential to the future design and control of TCO semiconductors, and their implementation into novel multifunctional devices.
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Affiliation(s)
- P D C King
- School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews KY16 9SS, UK.
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38
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King PDC, Rosen JA, Meevasana W, Tamai A, Rozbicki E, Comin R, Levy G, Fournier D, Yoshida Y, Eisaki H, Shen KM, Ingle NJC, Damascelli A, Baumberger F. Structural origin of apparent Fermi surface pockets in angle-resolved photoemission of Bi₂Sr(2-x)La(x)CuO(6+δ). Phys Rev Lett 2011; 106:127005. [PMID: 21517346 DOI: 10.1103/physrevlett.106.127005] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/26/2010] [Indexed: 05/30/2023]
Abstract
We observe apparent hole pockets in the Fermi surfaces of single-layer Bi-based cuprate superconductors from angle-resolved photoemission. From detailed low-energy electron diffraction measurements and an analysis of the angle-resolved photoemission polarization dependence, we show that these pockets are not intrinsic but arise from multiple overlapping superstructure replicas of the main and shadow bands. We further demonstrate that the hole pockets reported recently from angle-resolved photoemission [Meng et al., Nature (London) 462, 335 (2009)] have a similar structural origin and are inconsistent with an intrinsic hole pocket associated with the electronic structure of a doped CuO₂ plane.
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Affiliation(s)
- P D C King
- School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews, KY16 9SS, United Kingdom
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39
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Meevasana W, King PDC, He RH, Mo SK, Hashimoto M, Tamai A, Songsiriritthigul P, Baumberger F, Shen ZX. Creation and control of a two-dimensional electron liquid at the bare SrTiO3 surface. Nat Mater 2011; 10:114-8. [PMID: 21240289 DOI: 10.1038/nmat2943] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/15/2010] [Accepted: 12/10/2010] [Indexed: 05/24/2023]
Abstract
Many-body interactions in transition-metal oxides give rise to a wide range of functional properties, such as high-temperature superconductivity, colossal magnetoresistance or multiferroicity . The seminal recent discovery of a two-dimensional electron gas (2DEG) at the interface of the insulating oxides LaAlO(3) and SrTiO(3) (ref. 4) represents an important milestone towards exploiting such properties in all-oxide devices. This conducting interface shows a number of appealing properties, including a high electron mobility, superconductivity and large magnetoresistance, and can be patterned on the few-nanometre length scale. However, the microscopic origin of the interface 2DEG is poorly understood. Here, we show that a similar 2DEG, with an electron density as large as 8×10(13) cm(-2), can be formed at the bare SrTiO(3) surface. Furthermore, we find that the 2DEG density can be controlled through exposure of the surface to intense ultraviolet light. Subsequent angle-resolved photoemission spectroscopy measurements reveal an unusual coexistence of a light quasiparticle mass and signatures of strong many-body interactions.
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Affiliation(s)
- W Meevasana
- Department of Physics, Stanford University, California 94305, USA
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40
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King PDC, Veal TD, McConville CF, Zúñiga-Pérez J, Muñoz-Sanjosé V, Hopkinson M, Rienks EDL, Jensen MF, Hofmann P. Surface band-gap narrowing in quantized electron accumulation layers. Phys Rev Lett 2010; 104:256803. [PMID: 20867408 DOI: 10.1103/physrevlett.104.256803] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/15/2010] [Indexed: 05/29/2023]
Abstract
An energy gap between the valence and the conduction band is the defining property of a semiconductor, and the gap size plays a crucial role in the design of semiconductor devices. We show that the presence of a two-dimensional electron gas near to the surface of a semiconductor can significantly alter the size of its band gap through many-body effects caused by its high electron density, resulting in a surface band gap that is much smaller than that in the bulk. Apart from reconciling a number of disparate previous experimental findings, the results suggest an entirely new route to spatially inhomogeneous band-gap engineering.
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Affiliation(s)
- P D C King
- Department of Physics, University of Warwick, Coventry, CV4 7AL, United Kingdom.
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Tamai A, Ganin AY, Rozbicki E, Bacsa J, Meevasana W, King PDC, Caffio M, Schaub R, Margadonna S, Prassides K, Rosseinsky MJ, Baumberger F. Strong electron correlations in the normal state of the iron-based FeSe0.42Te0.58 superconductor observed by angle-resolved photoemission spectroscopy. Phys Rev Lett 2010; 104:097002. [PMID: 20367005 DOI: 10.1103/physrevlett.104.097002] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/29/2009] [Indexed: 05/29/2023]
Abstract
We investigate the normal state of the "11" iron-based superconductor FeSe0.42Te0.58 by angle-resolved photoemission. Our data reveal a highly renormalized quasiparticle dispersion characteristic of a strongly correlated metal. We find sheet dependent effective carrier masses between approximately 3 and 16m{e} corresponding to a mass enhancement over band structure values of m{*}/m{band} approximately 6-20. This is nearly an order of magnitude higher than the renormalization reported previously for iron-arsenide superconductors of the "1111" and "122" families but fully consistent with the bulk specific heat.
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Affiliation(s)
- A Tamai
- School of Physics and Astronomy, University of St. Andrews, St. Andrews, Fife KY16 9SS, United Kingdom
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42
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King PDC, Veal TD, McConville CF. Unintentional conductivity of indium nitride: transport modelling and microscopic origins. J Phys Condens Matter 2009; 21:174201. [PMID: 21825405 DOI: 10.1088/0953-8984/21/17/174201] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
A three-region model for the high n-type conductivity in InN, including contributions from the bulk, surface and buffer layer interface of the sample, is considered. In particular, a parallel conduction analysis is used to show that this model can account for the carrier concentration and mobility variation with film thickness that has previously been determined from single-field Hall effect measurements. Microscopic origins for the donors in each region are considered, and the overriding tendency towards n-type conductivity is discussed in terms of the bulk band structure of InN.
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Affiliation(s)
- P D C King
- Department of Physics, University of Warwick, Coventry CV4 7AL, UK
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43
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King PDC, Veal TD, McConville CF, King PJC, Cox SFJ, Celebi YG, Lichti RL. The donor nature of muonium in undoped, heavily n-type and p-type InAs. J Phys Condens Matter 2009; 21:075803. [PMID: 21817342 DOI: 10.1088/0953-8984/21/7/075803] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
The charge state of muonium has been investigated in p-type doped, nominally undoped (low n-type) and heavily n-type doped InAs. The donor Mu(+) state is shown to be the dominant defect in all cases. Consequently, muonium does not simply counteract the prevailing conductivity in this material. This is consistent with the charge neutrality level lying above the conduction band minimum in InAs.
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Affiliation(s)
- P D C King
- Department of Physics, University of Warwick, Coventry CV4 7AL, UK
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King PDC, Veal TD, Payne DJ, Bourlange A, Egdell RG, McConville CF. Surface electron accumulation and the charge neutrality level in In2O3. Phys Rev Lett 2008; 101:116808. [PMID: 18851315 DOI: 10.1103/physrevlett.101.116808] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/06/2008] [Indexed: 05/26/2023]
Abstract
High-resolution x-ray photoemission spectroscopy, infrared reflectivity and Hall effect measurements, combined with surface space-charge calculations, are used to show that electron accumulation occurs at the surface of undoped single-crystalline In2O3. From a combination of measurements performed on undoped and heavily Sn-doped samples, the charge neutrality level is shown to lie approximately 0.4 eV above the conduction band minimum in In2O3, explaining the electron accumulation at the surface of undoped material, the propensity for n-type conductivity, and the ease of n-type doping in In2O3, and hence its use as a transparent conducting oxide material.
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Affiliation(s)
- P D C King
- Department of Physics, University of Warwick, Coventry CV4 7AL, United Kingdom
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