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Walker M, Scott K, Boyle TJ, Byland JK, Bötzel S, Zhao Z, Day RP, Zhdanovich S, Gorovikov S, Pedersen TM, Klavins P, Damascelli A, Eremin IM, Gozar A, Taufour V, da Silva Neto EH. Electronic stripe patterns near the fermi level of tetragonal Fe(Se,S). NPJ Quantum Mater 2023; 8:60. [PMID: 38666239 PMCID: PMC11041788 DOI: 10.1038/s41535-023-00592-5] [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] [Figures] [Subscribe] [Scholar Register] [Received: 05/11/2023] [Accepted: 10/05/2023] [Indexed: 04/28/2024]
Abstract
FeSe1-xSx remains one of the most enigmatic systems of Fe-based superconductors. While much is known about the orthorhombic parent compound, FeSe, the tetragonal samples, FeSe1-xSx with x > 0.17, remain relatively unexplored. Here, we provide an in-depth investigation of the electronic states of tetragonal FeSe0.81S0.19, using scanning tunneling microscopy and spectroscopy (STM/S) measurements, supported by angle-resolved photoemission spectroscopy (ARPES) and theoretical modeling. We analyze modulations of the local density of states (LDOS) near and away from Fe vacancy defects separately and identify quasiparticle interference (QPI) signals originating from multiple regions of the Brillouin zone, including the bands at the zone corners. We also observe that QPI signals coexist with a much stronger LDOS modulation for states near the Fermi level whose period is independent of energy. Our measurements further reveal that this strong pattern appears in the STS measurements as short range stripe patterns that are locally two-fold symmetric. Since these stripe patterns coexist with four-fold symmetric QPI around Fe-vacancies, the origin of their local two-fold symmetry must be distinct from that of nematic states in orthorhombic samples. We explore several aspects related to the stripes, such as the role of S and Fe-vacancy defects, and whether they can be explained by QPI. We consider the possibility that the observed stripe patterns may represent incipient charge order correlations, similar to those observed in the cuprates.
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Affiliation(s)
- M. Walker
- Department of Physics and Astronomy, University of California, Davis, CA USA
- Department of Physics, Yale University, New Haven, CT USA
- Energy Sciences Institute, Yale University, West Haven, CT USA
| | - K. Scott
- Department of Physics, Yale University, New Haven, CT USA
- Energy Sciences Institute, Yale University, West Haven, CT USA
| | - T. J. Boyle
- Department of Physics and Astronomy, University of California, Davis, CA USA
- Department of Physics, Yale University, New Haven, CT USA
- Energy Sciences Institute, Yale University, West Haven, CT USA
| | - J. K. Byland
- Department of Physics and Astronomy, University of California, Davis, CA USA
| | - S. Bötzel
- Institut für Theoretische Physik III, Ruhr-Universität Bochum, Bochum, Germany
| | - Z. Zhao
- Department of Physics and Astronomy, University of California, Davis, CA USA
| | - R. P. Day
- Quantum Matter Institute, University of British Columbia, Vancouver, BC Canada
- Department of Physics & Astronomy, University of British Columbia, Vancouver, BC Canada
| | - S. Zhdanovich
- Quantum Matter Institute, University of British Columbia, Vancouver, BC Canada
- Department of Physics & Astronomy, University of British Columbia, Vancouver, BC Canada
| | - S. Gorovikov
- Canadian Light Source, Saskatoon, Saskatchewan Canada
| | | | - P. Klavins
- Department of Physics and Astronomy, University of California, Davis, CA USA
| | - A. Damascelli
- Quantum Matter Institute, University of British Columbia, Vancouver, BC Canada
- Department of Physics & Astronomy, University of British Columbia, Vancouver, BC Canada
| | - I. M. Eremin
- Institut für Theoretische Physik III, Ruhr-Universität Bochum, Bochum, Germany
| | - A. Gozar
- Department of Physics, Yale University, New Haven, CT USA
- Energy Sciences Institute, Yale University, West Haven, CT USA
| | - V. Taufour
- Department of Physics and Astronomy, University of California, Davis, CA USA
| | - E. H. da Silva Neto
- Department of Physics and Astronomy, University of California, Davis, CA USA
- Department of Physics, Yale University, New Haven, CT USA
- Energy Sciences Institute, Yale University, West Haven, CT USA
- Department of Applied Physics, Yale University, New Haven, CT USA
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Bekaert J, Bignardi L, Aperis A, van Abswoude P, Mattevi C, Gorovikov S, Petaccia L, Goldoni A, Partoens B, Oppeneer PM, Peeters FM, Milošević MV, Rudolf P, Cepek C. Free surfaces recast superconductivity in few-monolayer MgB 2: Combined first-principles and ARPES demonstration. Sci Rep 2017; 7:14458. [PMID: 29089566 PMCID: PMC5663715 DOI: 10.1038/s41598-017-13913-z] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [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: 06/02/2017] [Accepted: 10/02/2017] [Indexed: 11/08/2022] Open
Abstract
Two-dimensional materials are known to harbour properties very different from those of their bulk counterparts. Recent years have seen the rise of atomically thin superconductors, with a caveat that superconductivity is strongly depleted unless enhanced by specific substrates, intercalants or adatoms. Surprisingly, the role in superconductivity of electronic states originating from simple free surfaces of two-dimensional materials has remained elusive to date. Here, based on first-principles calculations, anisotropic Eliashberg theory, and angle-resolved photoemission spectroscopy (ARPES), we show that surface states in few-monolayer MgB2 make a major contribution to the superconducting gap spectrum and density of states, clearly distinct from the widely known, bulk-like σ- and π-gaps. As a proof of principle, we predict and measure the gap opening on the magnesium-based surface band up to a critical temperature as high as ~30 K for merely six monolayers thick MgB2. These findings establish free surfaces as an unavoidable ingredient in understanding and further tailoring of superconductivity in atomically thin materials.
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Affiliation(s)
- J Bekaert
- Department of Physics, University of Antwerp, Groenenborgerlaan 171, B-2020, Antwerp, Belgium.
| | - L Bignardi
- Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747AG, Groningen, The Netherlands
- Elettra Sincrotrone Trieste, Strada Statale 14 km.163.5, I-34149, Trieste, Italy
| | - A Aperis
- Department of Physics and Astronomy, Uppsala University, Box 516, SE-751 20, Uppsala, Sweden
| | - P van Abswoude
- Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747AG, Groningen, The Netherlands
| | - C Mattevi
- IOM-CNR, Laboratorio TASC, Strada Statale 14 km.163.5, I-34149, Trieste, Italy
- Department of Materials, Imperial College London, Exhibition road, SW7 2AZ, London, United Kingdom
| | - S Gorovikov
- Elettra Sincrotrone Trieste, Strada Statale 14 km.163.5, I-34149, Trieste, Italy
- Canadian Light Source Inc., 44 Innovation Blvd, Saskatoon, SK S7N 2V3, Canada
| | - L Petaccia
- Elettra Sincrotrone Trieste, Strada Statale 14 km.163.5, I-34149, Trieste, Italy
| | - A Goldoni
- Elettra Sincrotrone Trieste, Strada Statale 14 km.163.5, I-34149, Trieste, Italy
| | - B Partoens
- Department of Physics, University of Antwerp, Groenenborgerlaan 171, B-2020, Antwerp, Belgium
| | - P M Oppeneer
- Department of Physics and Astronomy, Uppsala University, Box 516, SE-751 20, Uppsala, Sweden
| | - F M Peeters
- Department of Physics, University of Antwerp, Groenenborgerlaan 171, B-2020, Antwerp, Belgium
| | - M V Milošević
- Department of Physics, University of Antwerp, Groenenborgerlaan 171, B-2020, Antwerp, Belgium.
| | - P Rudolf
- Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747AG, Groningen, The Netherlands.
| | - C Cepek
- IOM-CNR, Laboratorio TASC, Strada Statale 14 km.163.5, I-34149, Trieste, Italy
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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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Offi F, Iacobucci S, Petaccia L, Gorovikov S, Vilmercati P, Rizzo A, Ruocco A, Goldoni A, Stefani G, Panaccione G. The attenuation length of low energy electrons in Yb. J Phys Condens Matter 2010; 22:305002. [PMID: 21399353 DOI: 10.1088/0953-8984/22/30/305002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Photoelectron emission spectra in a photon energy range between 7.5 and 21 eV are measured for in situ grown polycrystalline Yb films. By comparing bulk and surface core level shifted 4f components we give an estimation of the effective attenuation length (EAL) for low energy (6-20 eV) electrons in Yb, establishing a moderate increase of the EAL upon electron energy decrease. The experimental EAL data are found to be a factor of four smaller than those predicted from the so-called 'universal curve'.
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Affiliation(s)
- F Offi
- CNISM and Dipartimento di Fisica, Università Roma Tre, Rome, Italy.
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Rodolakis F, Mansart B, Papalazarou E, Gorovikov S, Vilmercati P, Petaccia L, Goldoni A, Rueff JP, Lupi S, Metcalf P, Marsi M. Quasiparticles at the Mott transition in V2O3: wave vector dependence and surface attenuation. Phys Rev Lett 2009; 102:066805. [PMID: 19257621 DOI: 10.1103/physrevlett.102.066805] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/03/2008] [Indexed: 05/27/2023]
Abstract
We present an angle resolved photoemission study of V2O3, a prototype system for the observation of Mott transitions in correlated materials. We show that the spectral features corresponding to the quasiparticle peak in the metallic phase present a marked wave vector dependence, with a stronger intensity along the GammaZ direction. The analysis of their intensity for different probing depths shows the existence of a characteristic length scale for the attenuation of coherent electronic excitations at the surface. This length scale, which is larger than the thickness of the surface region as normally defined for noncorrelated electronic states, is found to increase when approaching the Mott transition. These results are in agreement with the behavior of quasiparticles at surfaces as predicted by Borghi et al.
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Affiliation(s)
- F Rodolakis
- Laboratoire de Physique des Solides, CNRS-UMR 8502, Université Paris-Sud, F-91405 Orsay, France
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Gustafson J, Borg M, Mikkelsen A, Gorovikov S, Lundgren E, Andersen JN. Identification of step atoms by high resolution core level spectroscopy. Phys Rev Lett 2003; 91:056102. [PMID: 12906608 DOI: 10.1103/physrevlett.91.056102] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/21/2003] [Indexed: 05/24/2023]
Abstract
Vicinal Rh(111) surfaces are studied with high resolution core level photoemission. We demonstrate the possibility to distinguish between the different kinds of surface atoms on these surfaces by virtue of their 3d core level binding energies. In particular, the low coordinated step atoms are found to exhibit a clear fingerprint in Rh 3d spectra. We demonstrate how this may be used to show that initial oxygen adsorption occurs on the steps and not on the terraces of the vicinal surfaces.
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Affiliation(s)
- J Gustafson
- Department of Synchrotron Radiation Research, Institute of Physics, Lund University, P.O. Box 118, SE-221 00 Lund, Sweden
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