1
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Kundu AK, Huang X, Seewald E, Ritz E, Pakhira S, Zhang S, Sun D, Turkel S, Shabani S, Yilmaz T, Vescovo E, Dean CR, Johnston DC, Valla T, Birol T, Basov DN, Fernandes RM, Pasupathy AN. Low-energy electronic structure in the unconventional charge-ordered state of ScV 6Sn 6. Nat Commun 2024; 15:5008. [PMID: 38866766 PMCID: PMC11169263 DOI: 10.1038/s41467-024-48883-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2023] [Accepted: 05/14/2024] [Indexed: 06/14/2024] Open
Abstract
Kagome vanadates AV3Sb5 display unusual low-temperature electronic properties including charge density waves (CDW), whose microscopic origin remains unsettled. Recently, CDW order has been discovered in a new material ScV6Sn6, providing an opportunity to explore whether the onset of CDW leads to unusual electronic properties. Here, we study this question using angle-resolved photoemission spectroscopy (ARPES) and scanning tunneling microscopy (STM). The ARPES measurements show minimal changes to the electronic structure after the onset of CDW. However, STM quasiparticle interference (QPI) measurements show strong dispersing features related to the CDW ordering vectors. A plausible explanation is the presence of a strong momentum-dependent scattering potential peaked at the CDW wavevector, associated with the existence of competing CDW instabilities. Our STM results further indicate that the bands most affected by the CDW are near vHS, analogous to the case of AV3Sb5 despite very different CDW wavevectors.
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Affiliation(s)
- Asish K Kundu
- Condensed Matter Physics and Materials Science Division, Brookhaven National Laboratory, Upton, NY, 11973, USA
| | - Xiong Huang
- Department of Physics, Columbia University, New York, NY, 10027, USA
| | - Eric Seewald
- Department of Physics, Columbia University, New York, NY, 10027, USA
| | - Ethan Ritz
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, MN, 55455, USA
| | - Santanu Pakhira
- Ames National Laboratory, Iowa State University, Ames, Iowa, 50011, USA
- Department of Physics, Maulana Azad National Institute of Technology, Bhopal, 462003, India
| | - Shuai Zhang
- Department of Physics, Columbia University, New York, NY, 10027, USA
| | - Dihao Sun
- Department of Physics, Columbia University, New York, NY, 10027, USA
| | - Simon Turkel
- Department of Physics, Columbia University, New York, NY, 10027, USA
| | - Sara Shabani
- Department of Physics, Columbia University, New York, NY, 10027, USA
| | - Turgut Yilmaz
- National Synchrotron Light Source II, Brookhaven National Laboratory, Upton, NY, 11973, USA
| | - Elio Vescovo
- National Synchrotron Light Source II, Brookhaven National Laboratory, Upton, NY, 11973, USA
| | - Cory R Dean
- Department of Physics, Columbia University, New York, NY, 10027, USA
| | - David C Johnston
- Ames National Laboratory, Iowa State University, Ames, Iowa, 50011, USA
- Department of Physics and Astronomy, Iowa State University, Ames, Iowa, 50011, USA
| | - Tonica Valla
- Donostia International Physics Center (DIPC), 20018, Donostia-San Sebastián, Spain
| | - Turan Birol
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, MN, 55455, USA
| | - Dmitri N Basov
- Department of Physics, Columbia University, New York, NY, 10027, USA
| | - Rafael M Fernandes
- School of Physics and Astronomy, University of Minnesota, Minneapolis, MN, 55455, USA
| | - Abhay N Pasupathy
- Condensed Matter Physics and Materials Science Division, Brookhaven National Laboratory, Upton, NY, 11973, USA.
- Department of Physics, Columbia University, New York, NY, 10027, USA.
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2
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Zhang Y, Lin LF, Moreo A, Maier TA, Dagotto E. Structural phase transition, s ±-wave pairing, and magnetic stripe order in bilayered superconductor La 3Ni 2O 7 under pressure. Nat Commun 2024; 15:2470. [PMID: 38503754 PMCID: PMC10951331 DOI: 10.1038/s41467-024-46622-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2023] [Accepted: 03/04/2024] [Indexed: 03/21/2024] Open
Abstract
Motivated by the recently discovered high-Tc superconductor La3Ni2O7, we comprehensively study this system using density functional theory and random phase approximation calculations. At low pressures, the Amam phase is stable, containing the Y2- mode distortion from the Fmmm phase, while the Fmmm phase is unstable. Because of small differences in enthalpy and a considerable Y2- mode amplitude, the two phases may coexist in the range between 10.6 and 14 GPa, beyond which the Fmmm phase dominates. In addition, the magnetic stripe-type spin order with wavevector (π, 0) was stable at the intermediate region. Pairing is induced in the s±-wave channel due to partial nesting between the M = (π, π) centered pockets and portions of the Fermi surface centered at the X = (π, 0) and Y = (0, π) points. This resembles results for iron-based superconductors but has a fundamental difference with iron pnictides and selenides. Moreover, our present efforts also suggest La3Ni2O7 is qualitatively different from infinite-layer nickelates and cuprate superconductors.
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Affiliation(s)
- Yang Zhang
- Department of Physics and Astronomy, University of Tennessee, Knoxville, TN, 37996, USA
| | - Ling-Fang Lin
- Department of Physics and Astronomy, University of Tennessee, Knoxville, TN, 37996, USA.
| | - Adriana Moreo
- Department of Physics and Astronomy, University of Tennessee, Knoxville, TN, 37996, USA
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - Thomas A Maier
- Computational Sciences and Engineering Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA.
| | - Elbio Dagotto
- Department of Physics and Astronomy, University of Tennessee, Knoxville, TN, 37996, USA.
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA.
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3
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Direct visualization of a static incommensurate antiferromagnetic order in Fe-doped Bi 2Sr 2CaCu 2O 8+δ. Proc Natl Acad Sci U S A 2021; 118:2115317118. [PMID: 34916295 DOI: 10.1073/pnas.2115317118] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/02/2021] [Indexed: 11/18/2022] Open
Abstract
In cuprate superconductors, due to strong electronic correlations, there are multiple intertwined orders which either coexist or compete with superconductivity. Among them, the antiferromagnetic (AF) order is the most prominent one. In the region where superconductivity sets in, the long-range AF order is destroyed. Yet the residual short-range AF spin fluctuations are present up to a much higher doping, and their role in the emergence of the superconducting phase is still highly debated. Here, by using a spin-polarized scanning tunneling microscope, we directly visualize an emergent incommensurate AF order in the nearby region of Fe impurities embedded in the optimally doped Bi2Sr2CaCu2O8+δ (Bi2212). Remarkably, the Fe impurities suppress the superconducting coherence peaks with the gapped feature intact, but pin down the ubiquitous short-range incommensurate AF order. Our work shows an intimate relation between antiferromagnetism and superconductivity.
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4
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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] [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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5
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Wang S, Choubey P, Chong YX, Chen W, Ren W, Eisaki H, Uchida S, Hirschfeld PJ, Davis JCS. Scattering interference signature of a pair density wave state in the cuprate pseudogap phase. Nat Commun 2021; 12:6087. [PMID: 34667154 PMCID: PMC8526682 DOI: 10.1038/s41467-021-26028-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2021] [Accepted: 09/09/2021] [Indexed: 11/21/2022] Open
Abstract
An unidentified quantum fluid designated the pseudogap (PG) phase is produced by electron-density depletion in the CuO2 antiferromagnetic insulator. Current theories suggest that the PG phase may be a pair density wave (PDW) state characterized by a spatially modulating density of electron pairs. Such a state should exhibit a periodically modulating energy gap [Formula: see text] in real-space, and a characteristic quasiparticle scattering interference (QPI) signature [Formula: see text] in wavevector space. By studying strongly underdoped Bi2Sr2CaDyCu2O8 at hole-density ~0.08 in the superconductive phase, we detect the 8a0-periodic [Formula: see text] modulations signifying a PDW coexisting with superconductivity. Then, by visualizing the temperature dependence of this electronic structure from the superconducting into the pseudogap phase, we find the evolution of the scattering interference signature [Formula: see text] that is predicted specifically for the temperature dependence of an 8a0-periodic PDW. These observations are consistent with theory for the transition from a PDW state coexisting with d-wave superconductivity to a pure PDW state in the Bi2Sr2CaDyCu2O8 pseudogap phase.
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Affiliation(s)
- Shuqiu Wang
- Clarendon Laboratory, University of Oxford, Oxford, UK
| | - Peayush Choubey
- Institut für Theoretische Physik III, Ruhr-Universität Bochum, Bochum, Germany
- Department of Physics, Indian Institute of Technology (Indian School of Mines), Dhanbad, Jharkhand, India
| | - Yi Xue Chong
- LASSP, Department of Physics, Cornell University, Ithaca, NY, USA
| | - Weijiong Chen
- Clarendon Laboratory, University of Oxford, Oxford, UK
| | - Wangping Ren
- Clarendon Laboratory, University of Oxford, Oxford, UK
| | - H Eisaki
- Institute of Advanced Industrial Science and Tech., Tsukuba, Ibaraki, Japan
| | - S Uchida
- Institute of Advanced Industrial Science and Tech., Tsukuba, Ibaraki, Japan
| | | | - J C Séamus Davis
- Clarendon Laboratory, University of Oxford, Oxford, UK.
- LASSP, Department of Physics, Cornell University, Ithaca, NY, USA.
- Department of Physics, University College Cork, Cork, Ireland.
- Max-Planck Institute for Chemical Physics of Solids, Dresden, Germany.
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6
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Massee F, Huang YK, Aprili M. Atomic manipulation of the gap in Bi 2Sr 2CaCu 2O 8+x. Science 2020; 367:68-71. [PMID: 31896712 DOI: 10.1126/science.aaw7964] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2019] [Accepted: 11/07/2019] [Indexed: 11/02/2022]
Abstract
Single-atom manipulation within doped correlated electron systems could help disentangle the influence of dopants, structural defects, and crystallographic characteristics on local electronic states. Unfortunately, the high diffusion barrier in these materials prevents conventional manipulation techniques. Here, we demonstrate the possibility to reversibly manipulate select sites in the optimally doped high-temperature superconductor Bi2Sr2CaCu2O8+x using the local electric field of the tip of a scanning tunneling microscope. We show that upon shifting individual Bi atoms at the surface, the spectral gap associated with superconductivity is seen to reversibly change by as much as 15 milli-electron volts (on average ~5% of the total gap size). Our toy model, which captures all observed characteristics, suggests that the electric field induces lateral movement of local pairing potentials in the CuO2 plane.
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Affiliation(s)
- F Massee
- Laboratoire de Physique des Solides, CNRS UMR 8502, Bâtiment 510, Université Paris-Sud, Université Paris-Saclay, 91405 Orsay, France.
| | - Y K Huang
- Institute of Physics, University of Amsterdam, 1098XH Amsterdam, Netherlands
| | - M Aprili
- Laboratoire de Physique des Solides, CNRS UMR 8502, Bâtiment 510, Université Paris-Sud, Université Paris-Saclay, 91405 Orsay, France
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7
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Liu C, Wang Z, Gao Y, Liu X, Liu Y, Wang QH, Wang J. Spectroscopic Imaging of Quasiparticle Bound States Induced by Strong Nonmagnetic Scatterings in One-Unit-Cell FeSe/SrTiO_{3}. PHYSICAL REVIEW LETTERS 2019; 123:036801. [PMID: 31386432 DOI: 10.1103/physrevlett.123.036801] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/24/2019] [Indexed: 06/10/2023]
Abstract
The absence of holelike Fermi pockets in the heavily electron-doped iron selenides (HEDISs) challenges the s_{±}-wave pairing originally proposed for iron pnictides, which consists of opposite signs of the gap function on electron and hole pockets. While the HEDIS compounds have been investigated extensively, a consistent description of the superconducting pairing therein is still lacking. Here, by in situ scanning tunneling spectroscopy and theoretical calculations, we study the effects of strong scatterings from nonmagnetic Pb adatoms on the epitaxially grown HEDIS, one-unit-cell FeSe/SrTiO_{3}(001). Systematic tunneling spectra measured on the Pb adatoms show comprehensive signals of quasiparticle bound states, which can be well explained theoretically within the sign-reversing pairing scenarios. The finding implies that, in addition to previously detected phonons, spin fluctuations play an important role in driving the Cooper pairing in FeSe/SrTiO_{3}(001). The sign reversal in the gap function we revealed here is a significant ingredient in a unified understanding of the high-temperature superconductivity in HEDISs.
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Affiliation(s)
- Chaofei Liu
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
| | - Ziqiao Wang
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
| | - Yi Gao
- Center for Quantum Transport and Thermal Energy Science, Jiangsu Key Lab on Opto-Electronic Technology, School of Physics and Technology, Nanjing Normal University, Nanjing 210023, China
| | - Xiaoqiang Liu
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
| | - Yi Liu
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
| | - Qiang-Hua Wang
- National Laboratory of Solid State Microstructures and School of Physics, Nanjing University, Nanjing 210093, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Jian Wang
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
- Collaborative Innovation Center of Quantum Matter, Beijing 100871, China
- CAS Center for Excellence in Topological Quantum Computation, University of Chinese Academy of Sciences, Beijing 100190, China
- Beijing Academy of Quantum Information Sciences, Beijing 100193, China
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8
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Gu Q, Wan S, Tang Q, Du Z, Yang H, Wang QH, Zhong R, Wen J, Gu GD, Wen HH. Directly visualizing the sign change of d-wave superconducting gap in Bi 2Sr 2CaCu 2O 8+δ by phase-referenced quasiparticle interference. Nat Commun 2019; 10:1603. [PMID: 30962440 PMCID: PMC6453940 DOI: 10.1038/s41467-019-09340-5] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2018] [Accepted: 03/07/2019] [Indexed: 11/29/2022] Open
Abstract
The superconducting state is formed by the condensation of Cooper pairs and protected by the superconducting gap. The pairing interaction between the two electrons of a Cooper pair determines the gap function. Thus, it is pivotal to detect the gap structure for understanding the mechanism of superconductivity. In cuprate superconductors, it has been well established that the gap may have a d-wave function. This gap function has an alternative sign change in the momentum space. It is however hard to visualize this sign change. Here we report the measurements of scanning tunneling spectroscopy in Bi2Sr2CaCu2O8+δ and conduct the analysis of phase-referenced quasiparticle interference (QPI). We see the seven basic scattering vectors that connect the octet ends of the banana-shaped contour of Fermi surface. The phase-referenced QPI clearly visualizes the sign change of the d-wave gap. Our results illustrate an effective way for determining the sign change of unconventional superconductors.
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Affiliation(s)
- Qiangqiang Gu
- National Laboratory of Solid State Microstructures and Department of Physics, Center for Superconducting Physics and Materials, Collaborative Innovation Center for Advanced Microstructures, Nanjing University, 210093, Nanjing, China
| | - Siyuan Wan
- National Laboratory of Solid State Microstructures and Department of Physics, Center for Superconducting Physics and Materials, Collaborative Innovation Center for Advanced Microstructures, Nanjing University, 210093, Nanjing, China
| | - Qingkun Tang
- National Laboratory of Solid State Microstructures and Department of Physics, Center for Superconducting Physics and Materials, Collaborative Innovation Center for Advanced Microstructures, Nanjing University, 210093, Nanjing, China
| | - Zengyi Du
- National Laboratory of Solid State Microstructures and Department of Physics, Center for Superconducting Physics and Materials, Collaborative Innovation Center for Advanced Microstructures, Nanjing University, 210093, Nanjing, China
| | - Huan Yang
- National Laboratory of Solid State Microstructures and Department of Physics, Center for Superconducting Physics and Materials, Collaborative Innovation Center for Advanced Microstructures, Nanjing University, 210093, Nanjing, China.
| | - Qiang-Hua Wang
- National Laboratory of Solid State Microstructures and Department of Physics, Center for Superconducting Physics and Materials, Collaborative Innovation Center for Advanced Microstructures, Nanjing University, 210093, Nanjing, China.
| | - Ruidan Zhong
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York, 11973, USA
| | - Jinsheng Wen
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York, 11973, USA
| | - G D Gu
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York, 11973, USA
| | - Hai-Hu Wen
- National Laboratory of Solid State Microstructures and Department of Physics, Center for Superconducting Physics and Materials, Collaborative Innovation Center for Advanced Microstructures, Nanjing University, 210093, Nanjing, China.
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9
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Massee F, Huang YK, Golden MS, Aprili M. Noisy defects in the high-T c superconductor Bi 2Sr 2CaCu 2O 8+x. Nat Commun 2019; 10:544. [PMID: 30710086 PMCID: PMC6358600 DOI: 10.1038/s41467-019-08518-1] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2018] [Accepted: 01/16/2019] [Indexed: 11/18/2022] Open
Abstract
Dopants and impurities are crucial in shaping the ground state of host materials: semiconducting technology is based on their ability to donate or trap electrons, and they can even be used to transform insulators into high temperature superconductors. Due to limited time resolution, most atomic-scale studies of the latter materials focussed on the effect of dopants on the electronic properties averaged over time. Here, by using atomic-scale current-noise measurements in optimally doped Bi2Sr2CaCu2O8+x, we visualize sub-nanometre sized objects where the tunnelling current-noise is enhanced by at least an order of magnitude. We show that these objects are previously undetected oxygen dopants whose ionization and local environment leads to unconventional charge dynamics resulting in correlated tunnelling events. The ionization of these dopants opens up new routes to dynamically control doping at the atomic scale, enabling the direct visualization of local charging on e.g. high-Tc superconductivity. The effects of dopants in high-temperature superconductors on the surrounding electronic structure give insights into their unconventional microscopic behaviour. Here the authors find a new class of defects that they identify as oxygen dopants whose ionization and local environment induce unusual atomic-scale charge dynamics.
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Affiliation(s)
- F Massee
- Laboratoire de Physique des Solides (CNRS UMR 8502), Bâtiment 510, Université Paris-Sud/Université Paris-Saclay, 91405, Orsay, France.
| | - Y K Huang
- Institute of Physics, University of Amsterdam, 1098 XH, Amsterdam, The Netherlands
| | - M S Golden
- Institute of Physics, University of Amsterdam, 1098 XH, Amsterdam, The Netherlands
| | - M Aprili
- Laboratoire de Physique des Solides (CNRS UMR 8502), Bâtiment 510, Université Paris-Sud/Université Paris-Saclay, 91405, Orsay, France
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10
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Iwaya K, Kohsaka Y, Okawa K, Machida T, Bahramy MS, Hanaguri T, Sasagawa T. Full-gap superconductivity in spin-polarised surface states of topological semimetal β-PdBi 2. Nat Commun 2017; 8:976. [PMID: 29042547 PMCID: PMC5730620 DOI: 10.1038/s41467-017-01209-9] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2017] [Accepted: 08/24/2017] [Indexed: 12/05/2022] Open
Abstract
A bulk superconductor possessing a topological surface state at the Fermi level is a promising system to realise long-sought topological superconductivity. Although several candidate materials have been proposed, experimental demonstrations concurrently exploring spin textures and superconductivity at the surface have remained elusive. Here we perform spectroscopic-imaging scanning tunnelling microscopy on the centrosymmetric superconductor β-PdBi2 that hosts a topological surface state. By combining first-principles electronic-structure calculations and quasiparticle interference experiments, we determine the spin textures at the surface, and show not only the topological surface state but also all other surface bands exhibit spin polarisations parallel to the surface. We find that the superconducting gap fully opens in all the spin-polarised surface states. This behaviour is consistent with a possible spin-triplet order parameter expected for such in-plane spin textures, but the observed superconducting gap amplitude is comparable to that of the bulk, suggesting that the spin-singlet component is predominant in β-PdBi2.Although several materials have been proposed as topological superconductors, spin textures and superconductivity at the surface remain elusive. Here, Iwaya et al. determine the spin textures at the surface of a superconductor β-PdBi2 and find the superconducting gap opening in all spin-polarised surface states.
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Affiliation(s)
- K Iwaya
- RIKEN Center for Emergent Matter Science, Wako, Saitama, 351-0198, Japan.
| | - Y Kohsaka
- RIKEN Center for Emergent Matter Science, Wako, Saitama, 351-0198, Japan
| | - K Okawa
- Laboratory for Materials and Structures, Tokyo Institute of Technology, Yokohama, Kanagawa, 226-8503, Japan
| | - T Machida
- RIKEN Center for Emergent Matter Science, Wako, Saitama, 351-0198, Japan
| | - M S Bahramy
- RIKEN Center for Emergent Matter Science, Wako, Saitama, 351-0198, Japan
- Department of Applied Physics, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan
| | - T Hanaguri
- RIKEN Center for Emergent Matter Science, Wako, Saitama, 351-0198, Japan.
| | - T Sasagawa
- Laboratory for Materials and Structures, Tokyo Institute of Technology, Yokohama, Kanagawa, 226-8503, Japan
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11
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Hlobil P, Jandke J, Wulfhekel W, Schmalian J. Tracing the Electronic Pairing Glue in Unconventional Superconductors via Inelastic Scanning Tunneling Spectroscopy. PHYSICAL REVIEW LETTERS 2017; 118:167001. [PMID: 28474901 DOI: 10.1103/physrevlett.118.167001] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/30/2016] [Indexed: 06/07/2023]
Abstract
Scanning tunneling microscopy has been shown to be a powerful experimental probe to detect electronic excitations and further allows us to deduce fingerprints of bosonic collective modes in superconductors. Here, we demonstrate that the inclusion of inelastic tunnel events is crucial for the interpretation of tunneling spectra of unconventional superconductors and allows us to directly probe electronic and bosonic excitations via scanning tunneling microscopy. We apply the formalism to the iron based superconductor LiFeAs. With the inclusion of inelastic contributions, we find strong evidence for a nonconventional pairing mechanism, likely via magnetic excitations.
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Affiliation(s)
- Patrik Hlobil
- Institut für Festkörperphysik, Karlsruher Institut für Technologie, 76344 Karlsruhe, Germany
- Institut für Theorie der Kondensierten Materie, Karlsruher Institut für Technologie, 76131 Karlsruhe, Germany
| | - Jasmin Jandke
- Physikalisches Institut, Karlsruher Institut für Technologie, 76131 Karlsruhe, Germany
| | - Wulf Wulfhekel
- Physikalisches Institut, Karlsruher Institut für Technologie, 76131 Karlsruhe, Germany
| | - Jörg Schmalian
- Institut für Festkörperphysik, Karlsruher Institut für Technologie, 76344 Karlsruhe, Germany
- Institut für Theorie der Kondensierten Materie, Karlsruher Institut für Technologie, 76131 Karlsruhe, Germany
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