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Hu B, Chen H, Ye Y, Huang Z, Han X, Zhao Z, Xiao H, Lin X, Yang H, Wang Z, Gao HJ. Evidence of a distinct collective mode in Kagome superconductors. Nat Commun 2024; 15:6109. [PMID: 39030195 PMCID: PMC11271580 DOI: 10.1038/s41467-024-50330-z] [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: 03/10/2024] [Accepted: 07/05/2024] [Indexed: 07/21/2024] Open
Abstract
The collective modes of the superconducting order parameter fluctuation can provide key insights into the nature of the superconductor. Recently, a family of superconductors has emerged in non-magnetic kagome materials AV3Sb5 (A = K, Rb, Cs), exhibiting fertile emergent phenomenology. However, the collective behaviors of Cooper pairs have not been studied. Here, we report a distinct collective mode in CsV3-xTaxSb5 using scanning tunneling microscope/spectroscopy. The spectral line-shape is well-described by one isotropic and one anisotropic superconducting gap, and a bosonic mode due to electron-mode coupling. With increasing x, the two gaps move closer in energy, merge into two isotropic gaps of equal amplitude, and then increase synchronously. The mode energy decreases monotonically to well below 2 Δ and survives even after the charge density wave order is suppressed. We propose the interpretation of this collective mode as Leggett mode between different superconducting components or the Bardasis-Schrieffer mode due to a subleading superconducting component.
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Affiliation(s)
- Bin Hu
- Beijing National Center for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, 100190, Beijing, PR China
- School of Physical Sciences, University of Chinese Academy of Sciences, 100190, Beijing, PR China
| | - Hui Chen
- Beijing National Center for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, 100190, Beijing, PR China
- School of Physical Sciences, University of Chinese Academy of Sciences, 100190, Beijing, PR China
- Hefei National Laboratory, 230088, Hefei, Anhui, PR China
| | - Yuhan Ye
- Beijing National Center for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, 100190, Beijing, PR China
- School of Physical Sciences, University of Chinese Academy of Sciences, 100190, Beijing, PR China
| | - Zihao Huang
- Beijing National Center for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, 100190, Beijing, PR China
- School of Physical Sciences, University of Chinese Academy of Sciences, 100190, Beijing, PR China
| | - Xianghe Han
- Beijing National Center for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, 100190, Beijing, PR China
- School of Physical Sciences, University of Chinese Academy of Sciences, 100190, Beijing, PR China
| | - Zhen Zhao
- Beijing National Center for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, 100190, Beijing, PR China
- School of Physical Sciences, University of Chinese Academy of Sciences, 100190, Beijing, PR China
| | - Hongqin Xiao
- Beijing National Center for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, 100190, Beijing, PR China
- School of Physical Sciences, University of Chinese Academy of Sciences, 100190, Beijing, PR China
| | - Xiao Lin
- Beijing National Center for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, 100190, Beijing, PR China
- School of Physical Sciences, University of Chinese Academy of Sciences, 100190, Beijing, PR China
| | - Haitao Yang
- Beijing National Center for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, 100190, Beijing, PR China
- School of Physical Sciences, University of Chinese Academy of Sciences, 100190, Beijing, PR China
| | - Ziqiang Wang
- Department of Physics, Boston College, Chestnut Hill, MA, 02467, USA.
| | - Hong-Jun Gao
- Beijing National Center for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, 100190, Beijing, PR China.
- School of Physical Sciences, University of Chinese Academy of Sciences, 100190, Beijing, PR China.
- Hefei National Laboratory, 230088, Hefei, Anhui, PR China.
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2
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Ding C, Wei Z, Dong W, Feng H, Shi M, Wang L, Jia JF, Xue QK. Atomic-Site-Dependent Pairing Gap in Monolayer FeSe/SrTiO 3(001)-(√13 × √13). NANO LETTERS 2024; 24:8445-8452. [PMID: 38917425 DOI: 10.1021/acs.nanolett.4c02627] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/27/2024]
Abstract
The interfacial FeSe/TiO2-δ coupling induces high-temperature superconductivity in monolayer FeSe films. Using cryogenic atomically resolved scanning tunneling microscopy/spectroscopy, we obtained atomic-site dependent surface density of states, work function, and the pairing gap in the monolayer FeSe on the SrTiO3(001)-(√13 × √13)-R33.7° surface. Our results disclosed the out-of-plane Se-Fe-Se triple layer gradient variation, switched DOS for Fe sites on and off TiO5□, and inequivalent Fe sublattices, which gives global spatial modulation of pairing gap contaminants with the (√13 × √13) pattern. Moreover, the coherent lattice coupling induces strong inversion asymmetry and in-plane anisotropy in the monolayer FeSe, which is demonstrated to correlate with the particle-hole asymmetry in coherence peaks. These results disclose delicate atomic-scale correlations between pairing and lattice-electronic coupling in the Bardeen-Cooper-Schrieffer to Bose-Einstein condensation crossover regime, providing insights into understanding the pairing mechanism of multiorbital superconductivity.
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Affiliation(s)
- Cui Ding
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
- Quantum Science Center of Guangdong-Hong Kong-Macao Greater Bay Area, Shenzhen 518045, China
| | - Zhongxu Wei
- Department of Physics, Southern University of Science and Technology, Shenzhen 518055, China
| | - Wenfeng Dong
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
| | - Hai Feng
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
| | - Mingxia Shi
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
| | - Lili Wang
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
- Frontier Science Center for Quantum Information, Beijing 100084, China
| | - Jin-Feng Jia
- Quantum Science Center of Guangdong-Hong Kong-Macao Greater Bay Area, Shenzhen 518045, China
- Department of Physics, Southern University of Science and Technology, Shenzhen 518055, China
- Department of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Qi-Kun Xue
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
- Quantum Science Center of Guangdong-Hong Kong-Macao Greater Bay Area, Shenzhen 518045, China
- Department of Physics, Southern University of Science and Technology, Shenzhen 518055, China
- Frontier Science Center for Quantum Information, Beijing 100084, China
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3
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He G, Li Y, Lei Y, Kreisel A, Andersen BM, Wang J. Lateral Quantum Confinement Effect on High-T C Superconducting FeSe Monolayer. NANO LETTERS 2024; 24:7654-7661. [PMID: 38865174 DOI: 10.1021/acs.nanolett.4c01435] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2024]
Abstract
Despite decades of research in spatially confined superconducting systems to understand the modification of superconductivity from reduced length scales, the investigation of the quantum confinement effect on high-temperature superconductors remains an outstanding challenge. Here, we report scanning tunneling spectroscopy measurements on laterally confined FeSe monolayers on SrTiO3 substrates, which are formed by epitaxially growing FeSe films with a coverage less than one unit cell. Comparing to the uniform regions of FeSe monolayers, the peninsula regions at the monolayer boundary exhibit reduced Fermi energy and undiminished superconductivity, leading to a putative crossover from a Bardeen-Cooper-Schrieffer state to a Bose-Einstein condensate state. In isolated FeSe monolayer islands, superconductivity is shown to exist in samples of smaller volume in contrast to conventional superconductors, while the validity of Anderson's criterion remains fulfilled. Our work reveals lateral quantum confinement effects in unconventional superconductors to enrich the understanding of high-temperature superconductivity in low-dimensional systems.
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Affiliation(s)
- Guanyang He
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
- ShanghaiTech Laboratory for Topological Physics, ShanghaiTech University, 201210 Shanghai, China
| | - Yu Li
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
| | - Yuxuan Lei
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
- Beijing Academy of Quantum Information Sciences, Beijing 100193, China
| | - Andreas Kreisel
- Niels Bohr Institute, University of Copenhagen, 2100 Copenhagen, Denmark
| | - Brian M Andersen
- Niels Bohr Institute, University of Copenhagen, 2100 Copenhagen, Denmark
| | - Jian Wang
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
- Collaborative Innovation Center of Quantum Matter, Beijing 100871, China
- Hefei National Laboratory, Hefei 230088, China
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4
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Gao Q, Bok JM, Ai P, Liu J, Yan H, Luo X, Cai Y, Li C, Wang Y, Yin C, Chen H, Gu G, Zhang F, Yang F, Zhang S, Peng Q, Zhu Z, Liu G, Xu Z, Xiang T, Zhao L, Choi HY, Zhou XJ. ARPES detection of superconducting gap sign in unconventional superconductors. Nat Commun 2024; 15:4538. [PMID: 38806466 PMCID: PMC11133361 DOI: 10.1038/s41467-024-48610-9] [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: 10/03/2023] [Accepted: 05/07/2024] [Indexed: 05/30/2024] Open
Abstract
The superconducting gap symmetry is crucial in understanding the underlying superconductivity mechanism. Angle-resolved photoemission spectroscopy (ARPES) has played a key role in determining the gap symmetry in unconventional superconductors. However, it has been considered so far that ARPES can only measure the magnitude of the superconducting gap but not its phase; the phase has to be detected by other phase-sensitive techniques. Here we propose a method to directly detect the superconducting gap sign by ARPES. This method is successfully validated in a cuprate superconductor Bi2Sr2CaCu2O8+δ with a well-known d-wave gap symmetry. When two bands have a strong interband interaction, the resulted electronic structures in the superconducting state are sensitive to the relative gap sign between the two bands. Our present work provides an approach to detect the gap sign and can be applied to various superconductors, particularly those with multiple orbitals like the iron-based superconductors.
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Affiliation(s)
- Qiang Gao
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
| | - Jin Mo Bok
- Department of Physics, Pohang University of Science and Technology (POSTECH), Pohang, 37673, Korea
| | - Ping Ai
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
| | - Jing Liu
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- Beijing Academy of Quantum Information Sciences, Beijing, 100193, China
| | - Hongtao Yan
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
| | - Xiangyu Luo
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Yongqing Cai
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
| | - Cong Li
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
| | - Yang Wang
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
| | - Chaohui Yin
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Hao Chen
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Genda Gu
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, NY, 11973, USA
| | - Fengfeng Zhang
- Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing, 100190, China
| | - Feng Yang
- Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing, 100190, China
| | - Shenjin Zhang
- Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing, 100190, China
| | - Qinjun Peng
- Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing, 100190, China
| | - Zhihai Zhu
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China
- Songshan Lake Materials Laboratory, Dongguan, Guangdong, 523808, China
| | - Guodong Liu
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China
- Songshan Lake Materials Laboratory, Dongguan, Guangdong, 523808, China
| | - Zuyan Xu
- Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing, 100190, China
| | - Tao Xiang
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- Beijing Academy of Quantum Information Sciences, Beijing, 100193, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Lin Zhao
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China.
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China.
- Songshan Lake Materials Laboratory, Dongguan, Guangdong, 523808, China.
| | - Han-Yong Choi
- Department of Physics and Institute for Basic Science Research, SungKyunKwan University, Suwon, 440-746, Korea.
| | - X J Zhou
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China.
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China.
- Songshan Lake Materials Laboratory, Dongguan, Guangdong, 523808, China.
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5
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Zhao D, Cui W, Liu Y, Gong G, Zhang L, Jia G, Zang Y, Hu X, Zhang D, Wang Y, Li W, Ji S, Wang L, He K, Ma X, Xue QK. Electronic inhomogeneity and phase fluctuation in one-unit-cell FeSe films. Nat Commun 2024; 15:3369. [PMID: 38643171 PMCID: PMC11032316 DOI: 10.1038/s41467-024-47350-0] [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: 06/19/2023] [Accepted: 03/25/2024] [Indexed: 04/22/2024] Open
Abstract
One-unit-cell FeSe films on SrTiO3 substrates are of great interest owing to significantly enlarged pairing gaps characterized by two coherence peaks at ±10 meV and ±20 meV. In-situ transport measurement is desired to reveal novel properties. Here, we performed in-situ microscale electrical transport and combined scanning tunneling microscopy measurements on continuous one-unit-cell FeSe films with twin boundaries. We observed two spatially coexisting superconducting phases in domains and on boundaries, characterized by distinct superconducting gaps (Δ 1 ~15 meV vs.Δ 2 ~10 meV) and pairing temperatures (Tp1~52.0 K vs. Tp2~37.3 K), and correspondingly two-step nonlinear V ~ I α behavior but a concurrent Berezinskii-Kosterlitz-Thouless (BKT)-like transition occurring atT BKT ~28.7 K. Moreover, the onset transition temperatureT c onset ~54 K and zero-resistivity temperatureT c zero ~31 K are consistent with Tp1 andT BKT , respectively. Our results indicate the broadened superconducting transition in FeSe/SrTiO3 is related to intrinsic electronic inhomogeneity due to distinct two-gap features and phase fluctuations of two-dimensional superconductivity.
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Affiliation(s)
- Dapeng Zhao
- Beijing Academy of Quantum Information Sciences, 100193, Beijing, China
| | - Wenqiang Cui
- Beijing Academy of Quantum Information Sciences, 100193, Beijing, China
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, 100084, Beijing, China
| | - Yaowu Liu
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, 100084, Beijing, China
| | - Guanming Gong
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, 100084, Beijing, China
| | - Liguo Zhang
- Beijing Academy of Quantum Information Sciences, 100193, Beijing, China
| | - Guihao Jia
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, 100084, Beijing, China
| | - Yunyi Zang
- Beijing Academy of Quantum Information Sciences, 100193, Beijing, China
| | - Xiaopeng Hu
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, 100084, Beijing, China
| | - Ding Zhang
- Beijing Academy of Quantum Information Sciences, 100193, Beijing, China
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, 100084, Beijing, China
- Frontier Science Center for Quantum Information, 100084, Beijing, China
| | - Yilin Wang
- School of Integrated Circuits, Shandong Technology Center of Nanodevices and Integration, State Key Laboratory of Crystal Materials, Shandong University, Jinan, 250100, China.
| | - Wei Li
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, 100084, Beijing, China
- Frontier Science Center for Quantum Information, 100084, Beijing, China
| | - Shuaihua Ji
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, 100084, Beijing, China
- Frontier Science Center for Quantum Information, 100084, Beijing, China
| | - Lili Wang
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, 100084, Beijing, China.
- Frontier Science Center for Quantum Information, 100084, Beijing, China.
| | - Ke He
- Beijing Academy of Quantum Information Sciences, 100193, Beijing, China
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, 100084, Beijing, China
- Frontier Science Center for Quantum Information, 100084, Beijing, China
| | - Xucun Ma
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, 100084, Beijing, China
- Frontier Science Center for Quantum Information, 100084, Beijing, China
| | - Qi-Kun Xue
- Beijing Academy of Quantum Information Sciences, 100193, Beijing, China.
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, 100084, Beijing, China.
- Frontier Science Center for Quantum Information, 100084, Beijing, China.
- Department of Physics, Southern University of Science and Technology, Shenzhen, 518055, China.
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6
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Wang S, Kennedy N, Fujita K, Uchida SI, Eisaki H, Johnson PD, Davis JCS, O'Mahony SM. Discovery of orbital ordering in Bi 2Sr 2CaCu 2O 8+x. NATURE MATERIALS 2024; 23:492-498. [PMID: 38438620 PMCID: PMC10990940 DOI: 10.1038/s41563-024-01817-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/25/2023] [Accepted: 01/22/2024] [Indexed: 03/06/2024]
Abstract
The primordial ingredient of cuprate superconductivity is the CuO2 unit cell. Theories usually concentrate on the intra-atom Coulombic interactions dominating the 3d9 and 3d10 configurations of each copper ion. However, if Coulombic interactions also occur between electrons of the 2p6 orbitals of each planar oxygen atom, spontaneous orbital ordering may split their energy levels. This long-predicted intra-unit-cell symmetry breaking should generate an orbitally ordered phase, for which the charge transfer energy ε separating the 2p6 and 3d10 orbitals is distinct for the two oxygen atoms. Here we introduce sublattice-resolved ε(r) imaging to CuO2 studies and discover intra-unit-cell rotational symmetry breaking of ε(r). Spatially, this state is arranged in disordered Ising domains of orthogonally oriented orbital order bounded by dopant ions, and within whose domain walls low-energy electronic quadrupolar two-level systems occur. Overall, these data reveal a Q = 0 orbitally ordered state that splits the oxygen energy levels by ~50 meV, in underdoped CuO2.
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Affiliation(s)
- Shuqiu Wang
- Clarendon Laboratory, University of Oxford, Oxford, UK.
- Department of Physics, Cornell University, Ithaca, NY, USA.
- H. H. Wills Physics Laboratory, University of Bristol, Bristol, UK.
| | - Niall Kennedy
- Clarendon Laboratory, University of Oxford, Oxford, UK
- School of Physics, University College Cork, Cork, Ireland
| | - Kazuhiro Fujita
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, NY, USA
| | | | - Hiroshi Eisaki
- National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Japan
| | - Peter D Johnson
- Clarendon Laboratory, University of Oxford, Oxford, UK
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, NY, USA
| | - J C Séamus Davis
- Clarendon Laboratory, University of Oxford, Oxford, UK.
- Department of Physics, Cornell University, Ithaca, NY, USA.
- School of Physics, University College Cork, Cork, Ireland.
- Max Planck Institute for Chemical Physics of Solids, Dresden, Germany.
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7
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Pasqualetti G, Bettermann O, Darkwah Oppong N, Ibarra-García-Padilla E, Dasgupta S, Scalettar RT, Hazzard KRA, Bloch I, Fölling S. Equation of State and Thermometry of the 2D SU(N) Fermi-Hubbard Model. PHYSICAL REVIEW LETTERS 2024; 132:083401. [PMID: 38457712 DOI: 10.1103/physrevlett.132.083401] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/30/2023] [Accepted: 01/09/2024] [Indexed: 03/10/2024]
Abstract
We characterize the equation of state (EoS) of the SU(N>2) Fermi-Hubbard Model (FHM) in a two-dimensional single-layer square optical lattice. We probe the density and the site occupation probabilities as functions of interaction strength and temperature for N=3, 4, and 6. Our measurements are used as a benchmark for state-of-the-art numerical methods including determinantal quantum Monte Carlo and numerical linked cluster expansion. By probing the density fluctuations, we compare temperatures determined in a model-independent way by fitting measurements to numerically calculated EoS results, making this a particularly interesting new step in the exploration and characterization of the SU(N) FHM.
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Affiliation(s)
- G Pasqualetti
- Ludwig-Maximilians-Universität, Schellingstraße 4, 80799 München, Germany
- Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Straße 1, 85748 Garching, Germany
- Munich Center for Quantum Science and Technology (MCQST), Schellingstraße 4, 80799 München, Germany
| | - O Bettermann
- Ludwig-Maximilians-Universität, Schellingstraße 4, 80799 München, Germany
- Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Straße 1, 85748 Garching, Germany
- Munich Center for Quantum Science and Technology (MCQST), Schellingstraße 4, 80799 München, Germany
| | - N Darkwah Oppong
- Ludwig-Maximilians-Universität, Schellingstraße 4, 80799 München, Germany
- Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Straße 1, 85748 Garching, Germany
- Munich Center for Quantum Science and Technology (MCQST), Schellingstraße 4, 80799 München, Germany
| | - E Ibarra-García-Padilla
- Department of Physics and Astronomy, Rice University, Houston, Texas 77005-1892, USA
- Rice Center for Quantum Materials, Rice University, Houston, Texas 77005-1892, USA
- Department of Physics, University of California, Davis, California 95616, USA
- Department of Physics and Astronomy, San José State University, San José, California 95192, USA
| | - S Dasgupta
- Department of Physics and Astronomy, Rice University, Houston, Texas 77005-1892, USA
- Rice Center for Quantum Materials, Rice University, Houston, Texas 77005-1892, USA
| | - R T Scalettar
- Department of Physics, University of California, Davis, California 95616, USA
| | - K R A Hazzard
- Department of Physics and Astronomy, Rice University, Houston, Texas 77005-1892, USA
- Rice Center for Quantum Materials, Rice University, Houston, Texas 77005-1892, USA
- Department of Physics, University of California, Davis, California 95616, USA
| | - I Bloch
- Ludwig-Maximilians-Universität, Schellingstraße 4, 80799 München, Germany
- Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Straße 1, 85748 Garching, Germany
- Munich Center for Quantum Science and Technology (MCQST), Schellingstraße 4, 80799 München, Germany
| | - S Fölling
- Ludwig-Maximilians-Universität, Schellingstraße 4, 80799 München, Germany
- Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Straße 1, 85748 Garching, Germany
- Munich Center for Quantum Science and Technology (MCQST), Schellingstraße 4, 80799 München, Germany
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8
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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 MATERIALS 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] [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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9
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Kim Y, Kim MS, Kim D, Kim M, Kim M, Cheng CM, Choi J, Jung S, Lu D, Kim JH, Cho S, Song D, Oh D, Yu L, Choi YJ, Kim HD, Han JH, Jo Y, Shim JH, Seo J, Huh S, Kim C. Kondo interaction in FeTe and its potential role in the magnetic order. Nat Commun 2023; 14:4145. [PMID: 37438375 PMCID: PMC10338437 DOI: 10.1038/s41467-023-39827-1] [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: 03/22/2022] [Accepted: 06/25/2023] [Indexed: 07/14/2023] Open
Abstract
Finding d-electron heavy fermion states has been an important topic as the diversity in d-electron materials can lead to many exotic Kondo effect-related phenomena or new states of matter such as correlation-driven topological Kondo insulator. Yet, obtaining direct spectroscopic evidence for a d-electron heavy fermion system has been elusive to date. Here, we report the observation of Kondo lattice behavior in an antiferromagnetic metal, FeTe, via angle-resolved photoemission spectroscopy, scanning tunneling spectroscopy and transport property measurements. The Kondo lattice behavior is represented by the emergence of a sharp quasiparticle and Fano-type tunneling spectra at low temperatures. The transport property measurements confirm the low-temperature Fermi liquid behavior and reveal successive coherent-incoherent crossover upon increasing temperature. We interpret the Kondo lattice behavior as a result of hybridization between localized Fe 3dxy and itinerant Te 5pz orbitals. Our observations strongly suggest unusual cooperation between Kondo lattice behavior and long-range magnetic order.
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Affiliation(s)
- Younsik Kim
- Center for Correlated Electron Systems, Institute for Basic Science, Seoul, 08826, Korea
- Department of Physics & Astronomy, Seoul National University, Seoul, 08826, Korea
| | - Min-Seok Kim
- Department of Emerging Materials Science, DGIST, Daegu, 42988, Korea
| | - Dongwook Kim
- Department of Chemistry, Pohang University of Science and Technology (POSTECH), Pohang, 37673, Korea
| | - Minjae Kim
- Korea Institute for Advanced Study, Seoul, 02455, Korea
| | - Minsoo Kim
- Center for Correlated Electron Systems, Institute for Basic Science, Seoul, 08826, Korea
- Department of Physics & Astronomy, Seoul National University, Seoul, 08826, Korea
| | - Cheng-Maw Cheng
- National Synchrotron Radiation Research Center, Hsinchu, 30076, Taiwan
| | - Joonyoung Choi
- Department of Physics, Kyungpook National University, Daegu, 41566, Korea
| | - Saegyeol Jung
- Center for Correlated Electron Systems, Institute for Basic Science, Seoul, 08826, Korea
- Department of Physics & Astronomy, Seoul National University, Seoul, 08826, Korea
| | - Donghui Lu
- Stanford Synchrotron Radiation Light Source, SLAC National Accelerator Laboratory, Menlo Park, CA, 94025, USA
| | - Jong Hyuk Kim
- Department of Physics, Yonsei University, Seoul, 03021, Korea
| | - Soohyun Cho
- Center for Excellence in Superconducting Electronics, State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, 200050, Shanghai, China
| | - Dongjoon Song
- Center for Correlated Electron Systems, Institute for Basic Science, Seoul, 08826, Korea
- Department of Physics & Astronomy, Seoul National University, Seoul, 08826, Korea
| | - Dongjin Oh
- Center for Correlated Electron Systems, Institute for Basic Science, Seoul, 08826, Korea
- Department of Physics & Astronomy, Seoul National University, Seoul, 08826, Korea
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
| | - Li Yu
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, 100190, Beijing, China
- School of Physical Sciences, University of Chinese Academy of Sciences, 100049, Beijing, China
- Songshan Lake Materials Laboratory, 523808, Dongguan, Guangdong, China
| | - Young Jai Choi
- Department of Physics, Yonsei University, Seoul, 03021, Korea
| | - Hyeong-Do Kim
- XFEL Beamline Division, Pohang Accelerator Laboratory, Pohang, 37673, Korea
| | - Jung Hoon Han
- Department of Physics, Sungkyunkwan University, Suwon, 16419, Korea
| | - Younjung Jo
- Department of Physics, Kyungpook National University, Daegu, 41566, Korea
| | - Ji Hoon Shim
- Department of Chemistry, Pohang University of Science and Technology (POSTECH), Pohang, 37673, Korea
| | - Jungpil Seo
- Department of Emerging Materials Science, DGIST, Daegu, 42988, Korea
| | - Soonsang Huh
- Center for Correlated Electron Systems, Institute for Basic Science, Seoul, 08826, Korea.
- Department of Physics & Astronomy, Seoul National University, Seoul, 08826, Korea.
| | - Changyoung Kim
- Center for Correlated Electron Systems, Institute for Basic Science, Seoul, 08826, Korea.
- Department of Physics & Astronomy, Seoul National University, Seoul, 08826, Korea.
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10
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Chen W, Neerup Breiø C, Massee F, Allan MP, Petrovic C, Davis JCS, Hirschfeld PJ, Andersen BM, Kreisel A. Interplay of hidden orbital order and superconductivity in CeCoIn 5. Nat Commun 2023; 14:2984. [PMID: 37225697 DOI: 10.1038/s41467-023-38760-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2022] [Accepted: 05/11/2023] [Indexed: 05/26/2023] Open
Abstract
Visualizing atomic-orbital degrees of freedom is a frontier challenge in scanned microscopy. Some types of orbital order are virtually imperceptible to normal scattering techniques because they do not reduce the overall crystal lattice symmetry. A good example is dxz/dyz (π,π) orbital order in tetragonal lattices. For enhanced detectability, here we consider the quasiparticle scattering interference (QPI) signature of such (π,π) orbital order in both normal and superconducting phases. The theory reveals that sublattice-specific QPI signatures generated by the orbital order should emerge strongly in the superconducting phase. Sublattice-resolved QPI visualization in superconducting CeCoIn5 then reveals two orthogonal QPI patterns at lattice-substitutional impurity atoms. We analyze the energy dependence of these two orthogonal QPI patterns and find the intensity peaked near E = 0, as predicted when such (π,π) orbital order is intertwined with d-wave superconductivity. Sublattice-resolved superconductive QPI techniques thus represent a new approach for study of hidden orbital order.
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Affiliation(s)
- Weijiong Chen
- Clarendon Laboratory, University of Oxford, Oxford, OX1 3PU, UK
| | - Clara Neerup Breiø
- Niels Bohr Institute, University of Copenhagen, 2100, Copenhagen, Denmark
| | - Freek Massee
- Laboratoire de Physique des Solides (CNRS UMR 8502), Bâtiment 510, Université Paris-Sud/Université Paris-Saclay, 91405, Orsay, France
| | - Milan P Allan
- Leiden Institute of Physics, Leiden University, P.O. Box 9504, 2300 RA, Leiden, The Netherlands
| | - Cedomir Petrovic
- CMPMS Department, Brookhaven National Laboratory, Upton, NY, 11973, USA
| | - J C Séamus Davis
- Clarendon Laboratory, University of Oxford, Oxford, OX1 3PU, UK.
- LASSP, Department of Physics, Cornell University, Ithaca, NY, 14850, USA.
- Department of Physics, University College Cork, Cork, T12 R5C, Ireland.
- Max-Planck Institute for Chemical Physics of Solids, 01187, Dresden, Germany.
| | - Peter J Hirschfeld
- Department of Physics, University of Florida, Gainesville, FL, 32611, USA
| | - Brian M Andersen
- Niels Bohr Institute, University of Copenhagen, 2100, Copenhagen, Denmark.
| | - Andreas Kreisel
- Niels Bohr Institute, University of Copenhagen, 2100, Copenhagen, Denmark
- Inst. für Theoretische Physik, Universität Leipzig, Brüderstr. 16, Leipzig, 04103, Germany
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11
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Matsuura K, Roppongi M, Qiu M, Sheng Q, Cai Y, Yamakawa K, Guguchia Z, Day RP, Kojima KM, Damascelli A, Sugimura Y, Saito M, Takenaka T, Ishihara K, Mizukami Y, Hashimoto K, Gu Y, Guo S, Fu L, Zhang Z, Ning F, Zhao G, Dai G, Jin C, Beare JW, Luke GM, Uemura YJ, Shibauchi T. Two superconducting states with broken time-reversal symmetry in FeSe 1-xS x. Proc Natl Acad Sci U S A 2023; 120:e2208276120. [PMID: 37186859 PMCID: PMC10214191 DOI: 10.1073/pnas.2208276120] [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: 05/13/2022] [Accepted: 04/12/2023] [Indexed: 05/17/2023] Open
Abstract
Iron-chalcogenide superconductors FeSe1-xSx possess unique electronic properties such as nonmagnetic nematic order and its quantum critical point. The nature of superconductivity with such nematicity is important for understanding the mechanism of unconventional superconductivity. A recent theory suggested the possible emergence of a fundamentally new class of superconductivity with the so-called Bogoliubov Fermi surfaces (BFSs) in this system. However, such an ultranodal pair state requires broken time-reversal symmetry (TRS) in the superconducting state, which has not been observed experimentally. Here, we report muon spin relaxation (μSR) measurements in FeSe1-xSx superconductors for 0 ≤ x ≤ 0.22 covering both orthorhombic (nematic) and tetragonal phases. We find that the zero-field muon relaxation rate is enhanced below the superconducting transition temperature Tc for all compositions, indicating that the superconducting state breaks TRS both in the nematic and tetragonal phases. Moreover, the transverse-field μSR measurements reveal that the superfluid density shows an unexpected and substantial reduction in the tetragonal phase (x > 0.17). This implies that a significant fraction of electrons remain unpaired in the zero-temperature limit, which cannot be explained by the known unconventional superconducting states with point or line nodes. The TRS breaking and the suppressed superfluid density in the tetragonal phase, together with the reported enhanced zero-energy excitations, are consistent with the ultranodal pair state with BFSs. The present results reveal two different superconducting states with broken TRS separated by the nematic critical point in FeSe1-xSx, which calls for the theory of microscopic origins that account for the relation between nematicity and superconductivity.
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Affiliation(s)
- Kohei Matsuura
- Department of Advanced Materials Science, University of Tokyo, Kashiwa277-8561, Japan
| | - Masaki Roppongi
- Department of Advanced Materials Science, University of Tokyo, Kashiwa277-8561, Japan
| | - Mingwei Qiu
- Department of Advanced Materials Science, University of Tokyo, Kashiwa277-8561, Japan
| | - Qi Sheng
- Department of Physics, Columbia University, New York, NY10027
| | - Yipeng Cai
- Quantum Matter Institute, University of British Columbia, Vancouver, BCV6T 1Z4, Canada
- Department of Physics & Astronomy, University of British Columbia, Vancouver, BCV6T 1Z1, Canada
| | | | - Zurab Guguchia
- Department of Physics, Columbia University, New York, NY10027
| | - Ryan P. Day
- Quantum Matter Institute, University of British Columbia, Vancouver, BCV6T 1Z4, Canada
- Department of Physics & Astronomy, University of British Columbia, Vancouver, BCV6T 1Z1, Canada
| | - Kenji M. Kojima
- Quantum Matter Institute, University of British Columbia, Vancouver, BCV6T 1Z4, Canada
- Centre for Molecular and Materials Science, TRIUMF, Vancouver, BCV6T 2A3, Canada
| | - Andrea Damascelli
- Quantum Matter Institute, University of British Columbia, Vancouver, BCV6T 1Z4, Canada
- Department of Physics & Astronomy, University of British Columbia, Vancouver, BCV6T 1Z1, Canada
| | - Yuichi Sugimura
- Department of Advanced Materials Science, University of Tokyo, Kashiwa277-8561, Japan
| | - Mikihiko Saito
- Department of Advanced Materials Science, University of Tokyo, Kashiwa277-8561, Japan
| | - Takaaki Takenaka
- Department of Advanced Materials Science, University of Tokyo, Kashiwa277-8561, Japan
| | - Kota Ishihara
- Department of Advanced Materials Science, University of Tokyo, Kashiwa277-8561, Japan
| | - Yuta Mizukami
- Department of Advanced Materials Science, University of Tokyo, Kashiwa277-8561, Japan
| | - Kenichiro Hashimoto
- Department of Advanced Materials Science, University of Tokyo, Kashiwa277-8561, Japan
| | - Yilun Gu
- Department of Physics, Zhejiang University, Hangzhou310027, China
| | - Shengli Guo
- Department of Physics, Zhejiang University, Hangzhou310027, China
| | - Licheng Fu
- Department of Physics, Zhejiang University, Hangzhou310027, China
| | - Zheneng Zhang
- Department of Physics, Zhejiang University, Hangzhou310027, China
| | - Fanlong Ning
- Department of Physics, Zhejiang University, Hangzhou310027, China
| | - Guoqiang Zhao
- Beijing National Laboratory for Condensed Matter Physics, Beijing100190, China
- Institute of Physics, Chinese Academy of Sciences, Beijing100190, China
- University of Chinese Academy of Sciences, Beijing100190, China
| | - Guangyang Dai
- Beijing National Laboratory for Condensed Matter Physics, Beijing100190, China
- Institute of Physics, Chinese Academy of Sciences, Beijing100190, China
- University of Chinese Academy of Sciences, Beijing100190, China
| | - Changqing Jin
- Beijing National Laboratory for Condensed Matter Physics, Beijing100190, China
- Institute of Physics, Chinese Academy of Sciences, Beijing100190, China
- University of Chinese Academy of Sciences, Beijing100190, China
| | - James W. Beare
- Department of Physics and Astronomy, McMaster University, Hamilton, ONL8S 4M1, Canada
| | - Graeme M. Luke
- Centre for Molecular and Materials Science, TRIUMF, Vancouver, BCV6T 2A3, Canada
- Department of Physics and Astronomy, McMaster University, Hamilton, ONL8S 4M1, Canada
| | | | - Takasada Shibauchi
- Department of Advanced Materials Science, University of Tokyo, Kashiwa277-8561, Japan
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12
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Zhang W, Zhang ZM, Nie JH, Gong BC, Cai M, Liu K, Lu ZY, Fu YS. Spin-Resolved Imaging of Antiferromagnetic Order in Fe 4 Se 5 Ultrathin Films on SrTiO 3. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2023; 35:e2209931. [PMID: 36790865 DOI: 10.1002/adma.202209931] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/27/2022] [Revised: 01/17/2023] [Indexed: 05/12/2023]
Abstract
Unraveling the magnetic order in iron chalcogenides and pnictides at atomic scale is pivotal for understanding their unconventional superconducting pairing mechanism, but is experimentally challenging. Here, by utilizing spin-polarized scanning tunneling microscopy, real-space spin contrasts are successfully resolved to exhibit atomically unidirectional stripes in Fe4 Se5 ultrathin films, the plausible closely related compound of bulk FeSe with ordered Fe-vacancies, which are grown by molecular beam epitaxy. As is substantiated by the first-principles electronic structure calculations, the spin contrast originates from a pair-checkerboard antiferromagnetic ground state with in-plane magnetization, which is modulated by a spin-lattice coupling. These measurements further identify three types of nanoscale antiferromagnetic domains with distinguishable spin contrasts, which are subject to thermal fluctuations into short-ranged patches at elevated temperatures. This work provides promising opportunities in understanding the emergent magnetic order and the electronic phase diagram for FeSe-derived superconductors.
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Affiliation(s)
- Wenhao Zhang
- School of Physics and Wuhan National High Magnetic Field Center, Huazhong University of Science and Technology, Wuhan, 430074, China
| | - Zhi-Mo Zhang
- School of Physics and Wuhan National High Magnetic Field Center, Huazhong University of Science and Technology, Wuhan, 430074, China
| | - Jin-Hua Nie
- School of Physics and Wuhan National High Magnetic Field Center, Huazhong University of Science and Technology, Wuhan, 430074, China
| | - Ben-Chao Gong
- Department of Physics and Beijing Key Laboratory of Opto-electronic Functional Materials & Micro-nano Devices, Renmin University of China, Beijing, 100872, China
| | - Min Cai
- School of Physics and Wuhan National High Magnetic Field Center, Huazhong University of Science and Technology, Wuhan, 430074, China
| | - Kai Liu
- Department of Physics and Beijing Key Laboratory of Opto-electronic Functional Materials & Micro-nano Devices, Renmin University of China, Beijing, 100872, China
| | - Zhong-Yi Lu
- Department of Physics and Beijing Key Laboratory of Opto-electronic Functional Materials & Micro-nano Devices, Renmin University of China, Beijing, 100872, China
| | - Ying-Shuang Fu
- School of Physics and Wuhan National High Magnetic Field Center, Huazhong University of Science and Technology, Wuhan, 430074, China
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13
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Li Y, Shen D, Kreisel A, Chen C, Wei T, Xu X, Wang J. Anisotropic Gap Structure and Sign Reversal Symmetry in Monolayer Fe(Se,Te). NANO LETTERS 2023; 23:140-147. [PMID: 36450010 DOI: 10.1021/acs.nanolett.2c03735] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
The iron-based superconductors are an ideal platform to reveal the enigma of the unconventional superconductivity and potential topological superconductivity. Among them, the monolayer Fe(Se,Te)/SrTiO3(001), which is proposed to be topological nontrivial, shows interface-enhanced high-temperature superconductivity in the two-dimensional limit. However, the experimental studies on the superconducting pairing mechanism of monolayer Fe(Se,Te) films are still limited. Here, by measuring the quasiparticle interference in monolayer Fe(Se,Te)/SrTiO3(001), we report the observation of the anisotropic structure of the large superconducting gap and the sign change of the superconducting gap on different electron pockets. The results are well consistent with the "bonding-antibonding" s±-wave pairing symmetry driven by spin fluctuations in conjunction with spin-orbit coupling. Our work is of basic significance not only for a unified superconducting formalism in the iron-based superconductors, but also for understanding of topological superconductivity in high-temperature superconductors.
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Affiliation(s)
- Yu Li
- International Center for Quantum Materials, School of Physics, Peking University, Beijing100871, China
| | - Dingyu Shen
- International Center for Quantum Materials, School of Physics, Peking University, Beijing100871, China
| | - Andreas Kreisel
- Institut für Theoretische Physik, Universität Leipzig, D-04103Leipzig, Germany
| | - Cheng Chen
- International Center for Quantum Materials, School of Physics, Peking University, Beijing100871, China
| | - Tianheng Wei
- International Center for Quantum Materials, School of Physics, Peking University, Beijing100871, China
| | - Xiaotong Xu
- International Center for Quantum Materials, School of Physics, Peking University, Beijing100871, China
| | - Jian Wang
- International Center for Quantum Materials, School of Physics, Peking University, Beijing100871, China
- Collaborative Innovation Center of Quantum Matter, Beijing100871, China
- CAS Center for Excellence in Topological Quantum Computation, University of Chinese Academy of Sciences, Beijing100190, China
- Beijing Academy of Quantum Information Sciences, Beijing100193, China
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14
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Unconventional localization of electrons inside of a nematic electronic phase. Proc Natl Acad Sci U S A 2022; 119:e2200405119. [PMID: 36256805 PMCID: PMC9618067 DOI: 10.1073/pnas.2200405119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Among iron-based superconductors, FeSe displays an anomalous electronic nematic state, strong electronic correlations, and orbitally dependent band shifts that can influence its superconducting pairing. Here, we report detailed magnetotransport studies of thin flakes of FeSe that reveal unconventional transport, in which the hole carriers remain highly mobile, whereas the mobility of the electron carriers is low, and weakly temperature dependent, inside the nematic phase. This suggests an unusual localization of negative charge carriers that may be caused by orbital-dependent enhanced correlations, scattering of spin fluctuations, and/or a topological electronic transition. As the superconductivity is suppressed by reducing the flake thickness, it suggests that the electron pockets participate actively in pairing. By doping, electron pockets expand, enabling high-Tc superconductivity. The magnetotransport behavior inside the nematic phase of bulk FeSe reveals unusual multiband effects that cannot be reconciled with a simple two-band approximation proposed by surface-sensitive spectroscopic probes. In order to understand the role played by the multiband electronic structure and the degree of two-dimensionality, we have investigated the electronic properties of exfoliated flakes of FeSe by reducing their thickness. Based on magnetotransport and Hall resistivity measurements, we assess the mobility spectrum that suggests an unusual asymmetry between the mobilities of the electrons and holes, with the electron carriers becoming localized inside the nematic phase. Quantum oscillations in magnetic fields up to 38 T indicate the presence of a hole-like quasiparticle with a lighter effective mass and a quantum scattering time three times shorter, as compared with bulk FeSe. The observed localization of negative charge carriers by reducing dimensionality can be driven by orbitally dependent correlation effects, enhanced interband spin fluctuations, or a Lifshitz-like transition, which affect mainly the electron bands. The electronic localization leads to a fragile two-dimensional superconductivity in thin flakes of FeSe, in contrast to the two-dimensional high-Tc induced with electron doping via dosing or using a suitable interface.
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15
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Orbital-selective hole and hole-pair formation and Bose condensation in high-temperature superconductors. J SOLID STATE CHEM 2022. [DOI: 10.1016/j.jssc.2022.123529] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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16
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Stepanov EA. Eliminating Orbital Selectivity from the Metal-Insulator Transition by Strong Magnetic Fluctuations. PHYSICAL REVIEW LETTERS 2022; 129:096404. [PMID: 36083639 DOI: 10.1103/physrevlett.129.096404] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/06/2022] [Accepted: 07/11/2022] [Indexed: 06/15/2023]
Abstract
The orbital-selective electronic behavior is one of the most remarkable manifestations of strong electronic correlations in multiorbital systems. A prominent example is the orbital-selective Mott transition (OSMT), which is characterized by the coexistence of localized electrons in some orbitals, and itinerant electrons in other orbitals. The state-of-the-art theoretical description of the OSMT in two- and three-dimensional systems is based on local nonperturbative approximations to electronic correlations provided by dynamical mean-field theory or slave spin method. In this work we go beyond this local picture and focus on the effect of spatial collective electronic fluctuations on the OSMT. To this aim, we consider a half-filled Hubbard-Kanamori model on a cubic lattice with two orbitals that have different bandwidths. We show that strong magnetic fluctuations that are inherent in this system prevent the OSMT and favor the Néel transition that occurs at the same critical temperature for both orbitals.
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Affiliation(s)
- Evgeny A Stepanov
- CPHT, CNRS, Ecole Polytechnique, Institut Polytechnique de Paris, F-91128 Palaiseau, France
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17
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Kreisel A, Andersen BM, Rømer AT, Eremin IM, Lechermann F. Superconducting Instabilities in Strongly Correlated Infinite-Layer Nickelates. PHYSICAL REVIEW LETTERS 2022; 129:077002. [PMID: 36018682 DOI: 10.1103/physrevlett.129.077002] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/22/2022] [Accepted: 07/19/2022] [Indexed: 06/15/2023]
Abstract
The discovery of superconductivity in infinite-layer nickelates has added a new family of materials to the fascinating growing class of unconventional superconductors. By incorporating the strongly correlated multiorbital nature of the low-energy electronic degrees of freedom, we compute the leading superconducting instability from magnetic fluctuations relevant for infinite-layer nickelates. Specifically, by properly including the doping dependence of the Ni d_{x^{2}-y^{2}} and d_{z^{2}} orbitals as well as the self-doping band, we uncover a transition from d-wave pairing symmetry to nodal s_{±} superconductivity, driven by strong fluctuations in the d_{z^{2}}-dominated orbital states. We discuss the properties of the resulting superconducting condensates in light of recent tunneling and penetration depth experiments probing the detailed superconducting gap structure of these materials.
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Affiliation(s)
- Andreas Kreisel
- Institut für Theoretische Physik, Universität Leipzig, D-04103 Leipzig, Germany
| | - Brian M Andersen
- Niels Bohr Institute, University of Copenhagen, 2100 Copenhagen, Denmark
| | - Astrid T Rømer
- Niels Bohr Institute, University of Copenhagen, 2100 Copenhagen, Denmark
| | - Ilya M Eremin
- Institut für Theoretische Physik III, Ruhr-Universität Bochum, D-44801 Bochum, Germany
| | - Frank Lechermann
- Institut für Theoretische Physik III, Ruhr-Universität Bochum, D-44801 Bochum, Germany
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18
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Liu C, Kreisel A, Zhong S, Li Y, Andersen BM, Hirschfeld P, Wang J. Orbital-Selective High-Temperature Cooper Pairing Developed in the Two-Dimensional Limit. NANO LETTERS 2022; 22:3245-3251. [PMID: 35416679 DOI: 10.1021/acs.nanolett.1c04863] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
For multiband superconductors, the orbital multiplicity yields orbital differentiation in normal-state properties and can lead to orbital-selective spin-fluctuation Cooper pairing. The orbital-selective phenomenon has become increasingly pivotal in clarifying the pairing "enigma", particularly for multiband high-temperature superconductors. Meanwhile, in one-unit-cell (1-UC) FeSe/SrTiO3, since the standard electron-hole Fermi pocket nesting scenario is inapplicable, the actual pairing mechanism is subject to intense debate. Here, by measuring high-resolution Bogoliubov quasiparticle interference, we report observations of highly anisotropic magnetic Cooper pairing in 1-UC FeSe. Theoretically, it is important to incorporate orbitally selective effects of electronic correlations within a spin-fluctuation pairing calculation, where the dxy orbital becomes coherence-suppressed. The resulting pairing gap is compatible with the experimental findings, which suggests that high-Tc Cooper pairing with orbital selectivity applies to 2D-limit 1-UC FeSe. Our findings imply the general existence of orbital selectivity in iron-based superconductors and the universal significance of electron correlations in high-Tc superconductors.
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Affiliation(s)
- Chaofei Liu
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, People's Republic of China
| | - Andreas Kreisel
- Institut für Theoretische Physik, Universität Leipzig, D-04103 Leipzig, Germany
| | - Shan Zhong
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, People's Republic of China
| | - Yu Li
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, People's Republic of China
| | - Brian M Andersen
- Niels Bohr Institute, University of Copenhagen, Jagtvej 128, DK-2200 Copenhagen, Denmark
| | - Peter Hirschfeld
- Department of Physics, University of Florida, Gainesville, Florida 32611, United States
| | - Jian Wang
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, People's Republic of China
- CAS Center for Excellence in Topological Quantum Computation, University of Chinese Academy of Sciences, Beijing 100190, People's Republic of China
- Beijing Academy of Quantum Information Sciences, Beijing 100193, People's Republic of China
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19
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Song J, Qin Y, Wang Y, Cao C. Superconductivity and topologically nontrivial states in noncentrosymmetric XVSe 2 (X = Pb, Sn): a first-principles study. Phys Chem Chem Phys 2022; 24:1770-1778. [PMID: 34985071 DOI: 10.1039/d1cp04111h] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Noncentrosymmetric superconductors are strong candidates for exploring intrinsic topological superconductivity. Here, we predict two new noncentrosymmetric superconductors SnVSe2 and PbVSe2 by a systematic first-principles study. These two compounds show good thermal and dynamic stabilities. Moreover, the band topology of both compounds is predicted to be nontrivial via Z2 calculation and slab models. We also investigate the electron-phonon interactions in SnVSe2 and PbVSe2, indicating the Tc of SnVSe2 and PbVSe2 without external pressure are predicted to be ∼1.18 K and ∼0.22 K, respectively. Furthermore, the results on pressure engineering in PbVSe2 imply that the Tc of PbVSe2 can be tuned to 2.39 K for enhanced contributions from Pb layers under pressure up to 6.4 GPa. This work may provide new platforms for probing spin-triplet paring and may help with designing and developing new metal-intercalated transition metal dichalcogenides.
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Affiliation(s)
- Jiexi Song
- Research and Development Institute of Northwestern Polytechnical University in Shenzhen, Shenzhen 518057, China. .,MOE Key Laboratory of Materials Physics and Chemistry under Extraordinary Conditions and Shaanxi Key Laboratory of Condensed Matter Structures and Properties, School of Physical Science and Technology, Northwestern Polytechnical University, Xian 710072, China
| | - Yanqing Qin
- Research and Development Institute of Northwestern Polytechnical University in Shenzhen, Shenzhen 518057, China. .,MOE Key Laboratory of Materials Physics and Chemistry under Extraordinary Conditions and Shaanxi Key Laboratory of Condensed Matter Structures and Properties, School of Physical Science and Technology, Northwestern Polytechnical University, Xian 710072, China
| | - Yaocen Wang
- Research and Development Institute of Northwestern Polytechnical University in Shenzhen, Shenzhen 518057, China. .,MOE Key Laboratory of Materials Physics and Chemistry under Extraordinary Conditions and Shaanxi Key Laboratory of Condensed Matter Structures and Properties, School of Physical Science and Technology, Northwestern Polytechnical University, Xian 710072, China
| | - Chongde Cao
- Research and Development Institute of Northwestern Polytechnical University in Shenzhen, Shenzhen 518057, China. .,MOE Key Laboratory of Materials Physics and Chemistry under Extraordinary Conditions and Shaanxi Key Laboratory of Condensed Matter Structures and Properties, School of Physical Science and Technology, Northwestern Polytechnical University, Xian 710072, China
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20
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Iron pnictides and chalcogenides: a new paradigm for superconductivity. Nature 2022; 601:35-44. [PMID: 34987212 DOI: 10.1038/s41586-021-04073-2] [Citation(s) in RCA: 30] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2021] [Accepted: 09/29/2021] [Indexed: 11/09/2022]
Abstract
Superconductivity is a remarkably widespread phenomenon that is observed in most metals cooled to very low temperatures. The ubiquity of such conventional superconductors, and the wide range of associated critical temperatures, is readily understood in terms of the well-known Bardeen-Cooper-Schrieffer theory. Occasionally, however, unconventional superconductors are found, such as the iron-based materials, which extend and defy this understanding in unexpected ways. In the case of the iron-based superconductors, this includes the different ways in which the presence of multiple atomic orbitals can manifest in unconventional superconductivity, giving rise to a rich landscape of gap structures that share the same dominant pairing mechanism. In addition, these materials have also led to insights into the unusual metallic state governed by the Hund's interaction, the control and mechanisms of electronic nematicity, the impact of magnetic fluctuations and quantum criticality, and the importance of topology in correlated states. Over the fourteen years since their discovery, iron-based superconductors have proven to be a testing ground for the development of novel experimental tools and theoretical approaches, both of which have extensively influenced the wider field of quantum materials.
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21
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Abstract
Superconductivity has been discovered recently in infinite-layer nickel-based 112 thin films R1−xAxNiO2 (R = La, Nd, Pr and A = Sr, Ca). They are isostructural to the infinite-layer cuprate (Ca,Sr)CuO2 and are supposed to have a formal Ni 3d9 valence, thus providing a new platform to study the unconventional pairing mechanism of high-temperature superconductors. This important discovery immediately triggers a huge amount of innovative scientific curiosity in the field. In this paper, we try to give an overview of the recent research progress on the newly found superconducting nickelate systems, both from experimental and theoretical aspects. We mainly focus on the electronic structures, magnetic excitations, phase diagrams and superconducting gaps, and finally make some open discussions for possible pairing symmetries in Ni-based 112 systems. The infinite-layer nickel-based 112 thin films R1−xAxNiO2 can host superconductivity up to 15 K R1−xAxNiO2 is a multiband system, in which the short-range antiferromagnetic fluctuations can be detected R1−xAxNiO2 has an unconventional superconducting pairing sate with a robust d-wave gap and a full gap without unified understanding The nickelate system provides a new platform for researching unconventional superconductivity
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22
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On the Superconducting Critical Temperature of Heavily Disordered Interfaces Hosting Multi-Gap Superconductivity. COATINGS 2021. [DOI: 10.3390/coatings12010030] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
LaAlO3/SrTiO3 interfaces are a nice example of a two-dimensional electron gas, whose carrier density can be varied by top- and back-gating techniques. Due to the electron confinement near the interface, the two-dimensional band structure is split into sub-bands, and more than one sub-band can be filled when the carrier density increases. These interfaces also host superconductivity, and the interplay of two-dimensionality, multi-band character, with the possible occurrence of multi-gap superconductivity and disorder calls for a better understanding of finite-bandwidth effects on the superconducting critical temperature of heavily disordered multi-gap superconductors.
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23
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Kasahara S, Suzuki H, Machida T, Sato Y, Ukai Y, Murayama H, Suetsugu S, Kasahara Y, Shibauchi T, Hanaguri T, Matsuda Y. Quasiparticle Nodal Plane in the Fulde-Ferrell-Larkin-Ovchinnikov State of FeSe. PHYSICAL REVIEW LETTERS 2021; 127:257001. [PMID: 35029441 DOI: 10.1103/physrevlett.127.257001] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/08/2021] [Accepted: 11/16/2021] [Indexed: 06/14/2023]
Abstract
The Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state, characterized by Cooper pairs condensed at finite momentum, has been a long-sought state that remains unresolved in many classes of fermionic systems, including superconductors and ultracold atoms. A fascinating aspect of the FFLO state is the emergence of periodic nodal planes in real space, but its observation is still lacking. Here we investigate the superconducting order parameter at high magnetic fields H applied perpendicular to the ab plane in a high-purity single crystal of FeSe. The heat capacity and magnetic torque provide thermodynamic evidence for a distinct superconducting phase at the low-temperature/high-field corner of the phase diagram. Despite the bulk superconductivity, spectroscopic-imaging scanning tunneling microscopy performed on the same crystal demonstrates that the order parameter vanishes at the surface upon entering the high-field phase. These results provide the first demonstration of a pinned planar node perpendicular to H, which is consistent with a putative FFLO state.
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Affiliation(s)
- S Kasahara
- Department of Physics, Kyoto University, Kyoto 606-8502, Japan
- Research Institute for Interdisciplinary Science, Okayama University, Okayama 700-8530, Japan
| | - H Suzuki
- Department of Physics, Kyoto University, Kyoto 606-8502, Japan
| | - T Machida
- RIKEN Center for Emergent Matter Science, Wako, Saitama 351-0198, Japan
| | - Y Sato
- Department of Physics, Kyoto University, Kyoto 606-8502, Japan
- RIKEN Center for Emergent Matter Science, Wako, Saitama 351-0198, Japan
| | - Y Ukai
- Department of Physics, Kyoto University, Kyoto 606-8502, Japan
| | - H Murayama
- Department of Physics, Kyoto University, Kyoto 606-8502, Japan
| | - S Suetsugu
- Department of Physics, Kyoto University, Kyoto 606-8502, Japan
| | - Y Kasahara
- Department of Physics, Kyoto University, Kyoto 606-8502, Japan
| | - T Shibauchi
- Department of Advanced Materials Science, University of Tokyo, Chiba 277-8561, Japan
| | - T Hanaguri
- RIKEN Center for Emergent Matter Science, Wako, Saitama 351-0198, Japan
| | - Y Matsuda
- Department of Physics, Kyoto University, Kyoto 606-8502, Japan
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24
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Xu HS, Yan YJ, Yin R, Xia W, Fang S, Chen Z, Li Y, Yang W, Guo Y, Feng DL. Multiband Superconductivity with Sign-Preserving Order Parameter in Kagome Superconductor CsV_{3}Sb_{5}. PHYSICAL REVIEW LETTERS 2021; 127:187004. [PMID: 34767411 DOI: 10.1103/physrevlett.127.187004] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/27/2021] [Revised: 08/13/2021] [Accepted: 09/30/2021] [Indexed: 05/12/2023]
Abstract
The superconductivity of a kagome superconductor CsV_{3}Sb_{5} is studied by scanning tunneling microscopy and spectroscopy at ultralow temperature with high resolution. Two kinds of superconducting gaps with multiple sets of coherent peaks and residual zero-energy density of states (DOS) are observed on both half-Cs and Sb surfaces, implying multiband superconductivity. In addition, in-gap states can be induced by magnetic impurities but not by nonmagnetic impurities, suggesting a sign-preserving or s-wave superconducting order parameter. Moreover, the interplay between charge density waves (CDW) and superconductivity differs on various bands, resulting in different density-of-states distributions. Our results suggest that the superconducting gap is likely isotropic on the sections of Fermi surface that play little roles in CDW, and the superconducting gaps on the sections of Fermi surface with anisotropic CDW gaps are likely anisotropic as well. The residual spectral weights at zero energy are attributed to the extremely small superconducting gap on the tiny oval Fermi pockets. Our study provides critical clues for further understanding the superconductivity and its relation to CDW in CsV_{3}Sb_{5}.
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Affiliation(s)
- Han-Shu Xu
- Hefei National Laboratory for Physical Sciences at the Microscale and Department of Physics, University of Science and Technology of China, Hefei 230026, China
| | - Ya-Jun Yan
- Hefei National Laboratory for Physical Sciences at the Microscale and Department of Physics, University of Science and Technology of China, Hefei 230026, China
| | - Ruotong Yin
- Hefei National Laboratory for Physical Sciences at the Microscale and Department of Physics, University of Science and Technology of China, Hefei 230026, China
| | - Wei Xia
- School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, China
- ShanghaiTech Laboratory for Topological Physics, ShanghaiTech University, Shanghai 201210, China
| | - Shijie Fang
- Hefei National Laboratory for Physical Sciences at the Microscale and Department of Physics, University of Science and Technology of China, Hefei 230026, China
| | - Ziyuan Chen
- Hefei National Laboratory for Physical Sciences at the Microscale and Department of Physics, University of Science and Technology of China, Hefei 230026, China
| | - Yuanji Li
- Hefei National Laboratory for Physical Sciences at the Microscale and Department of Physics, University of Science and Technology of China, Hefei 230026, China
| | - Wenqi Yang
- Hefei National Laboratory for Physical Sciences at the Microscale and Department of Physics, University of Science and Technology of China, Hefei 230026, China
| | - Yanfeng Guo
- ShanghaiTech Laboratory for Topological Physics, ShanghaiTech University, Shanghai 201210, China
| | - Dong-Lai Feng
- Hefei National Laboratory for Physical Sciences at the Microscale and Department of Physics, University of Science and Technology of China, Hefei 230026, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing 210093, China
- Shanghai Research Center for Quantum Sciences, Shanghai 201315, China
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25
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Kuwayama T, Matsuura K, Gouchi J, Yamakawa Y, Mizukami Y, Kasahara S, Matsuda Y, Shibauchi T, Kontani H, Uwatoko Y, Fujiwara N. Pressure-induced reconstitution of Fermi surfaces and spin fluctuations in S-substituted FeSe. Sci Rep 2021; 11:17265. [PMID: 34446750 PMCID: PMC8390510 DOI: 10.1038/s41598-021-96277-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2021] [Accepted: 08/04/2021] [Indexed: 11/19/2022] Open
Abstract
FeSe is a unique high-\documentclass[12pt]{minimal}
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\begin{document}$$T_c$$\end{document}Tc iron-based superconductor in which nematicity, superconductivity, and magnetism are entangled with each other in the P-T phase diagram. We performed \documentclass[12pt]{minimal}
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\begin{document}$$^{77}$$\end{document}77Se-nuclear magnetic resonance measurements under pressures of up to 3.9 GPa on 12% S-substituted FeSe, in which the complex overlap between the nematicity and magnetism are resolved. A pressure-induced Lifshitz transition was observed at 1.0 GPa as an anomaly of the density of states and as double superconducting (SC) domes accompanied by different types of antiferromagnetic (AF) fluctuations. The low-\documentclass[12pt]{minimal}
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\begin{document}$$T_{\mathrm{c}}$$\end{document}Tc SC dome below 1 GPa is accompanied by strong AF fluctuations, whereas the high-\documentclass[12pt]{minimal}
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\begin{document}$$T_{\mathrm{c}}$$\end{document}Tc SC dome develops above 1 GPa, where AF fluctuations are fairly weak. These results suggest the importance of the \documentclass[12pt]{minimal}
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\begin{document}$$d_{xy}$$\end{document}dxy orbital and its intra-orbital coupling for the high-\documentclass[12pt]{minimal}
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\begin{document}$$T_{\mathrm{c}}$$\end{document}Tc superconductivity.
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Affiliation(s)
- T Kuwayama
- Graduate School of Human and Environmental Studies, Kyoto University, Yoshida-Nihonmatsu-cyo, Sakyo-ku, Kyoto, 606-8501, Japan
| | - K Matsuura
- Graduate School of Frontier Sciences, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba, 277-8581, Japan.,Research Center for Advanced Science and Technology, University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo, 153-8904, Japan
| | - J Gouchi
- Institute for Solid State Physics, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba, 277-8581, Japan
| | - Y Yamakawa
- Department of Physics, Nagoya University, Furo-cho, Nagoya, 464-8602, Japan
| | - Y Mizukami
- Graduate School of Frontier Sciences, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba, 277-8581, Japan
| | - S Kasahara
- Division of Physics and Astronomy, Graduate School of Science, Kyoto University, Kitashirakawa Oiwake-cho, Sakyo-ku, Kyoto, 606-8502, Japan.,Department of Physics, Okayama University, Okayama, 700-8530, Japan
| | - Y Matsuda
- Division of Physics and Astronomy, Graduate School of Science, Kyoto University, Kitashirakawa Oiwake-cho, Sakyo-ku, Kyoto, 606-8502, Japan
| | - T Shibauchi
- Graduate School of Frontier Sciences, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba, 277-8581, Japan
| | - H Kontani
- Department of Physics, Nagoya University, Furo-cho, Nagoya, 464-8602, Japan
| | - Y Uwatoko
- Institute for Solid State Physics, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba, 277-8581, Japan
| | - N Fujiwara
- Graduate School of Human and Environmental Studies, Kyoto University, Yoshida-Nihonmatsu-cyo, Sakyo-ku, Kyoto, 606-8501, Japan.
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26
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Quadrupolar charge dynamics in the nonmagnetic FeSe 1-x S x superconductors. Proc Natl Acad Sci U S A 2021; 118:2020585118. [PMID: 33980712 DOI: 10.1073/pnas.2020585118] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
We use polarization-resolved electronic Raman spectroscopy to study quadrupolar charge dynamics in a nonmagnetic [Formula: see text] superconductor. We observe two types of long-wavelength [Formula: see text] symmetry excitations: 1) a low-energy quasi-elastic scattering peak (QEP) and 2) a broad electronic continuum with a maximum at 55 meV. Below the tetragonal-to-orthorhombic structural transition at [Formula: see text], a pseudogap suppression with temperature dependence reminiscent of the nematic order parameter develops in the [Formula: see text] symmetry spectra of the electronic excitation continuum. The QEP exhibits critical enhancement upon cooling toward [Formula: see text] The intensity of the QEP grows with increasing sulfur concentration x and maximizes near critical concentration [Formula: see text], while the pseudogap size decreases with the suppression of [Formula: see text] We interpret the development of the pseudogap in the quadrupole scattering channel as a manifestation of transition from the non-Fermi liquid regime, dominated by strong Pomeranchuk-like fluctuations giving rise to intense electronic continuum of excitations in the fourfold symmetric high-temperature phase, to the Fermi liquid regime in the broken-symmetry nematic phase where the quadrupole fluctuations are suppressed.
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27
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Koch RJ, Sinclair R, McDonnell MT, Yu R, Abeykoon M, Tucker MG, Tsvelik AM, Billinge SJL, Zhou HD, Yin WG, Bozin ES. Dual Orbital Degeneracy Lifting in a Strongly Correlated Electron System. PHYSICAL REVIEW LETTERS 2021; 126:186402. [PMID: 34018766 DOI: 10.1103/physrevlett.126.186402] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/29/2020] [Accepted: 03/29/2021] [Indexed: 06/12/2023]
Abstract
The local structure of NaTiSi_{2}O_{6} is examined across its Ti-dimerization orbital-assisted Peierls transition at 210 K. An atomic pair distribution function approach evidences local symmetry breaking preexisting far above the transition. The analysis unravels that, on warming, the dimers evolve into a short range orbital degeneracy lifted (ODL) state of dual orbital character, persisting up to at least 490 K. The ODL state is correlated over the length scale spanning ∼6 sites of the Ti zigzag chains. Results imply that the ODL phenomenology extends to strongly correlated electron systems.
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Affiliation(s)
- R J Koch
- Condensed Matter Physics and Materials Science Division, Brookhaven National Laboratory, Upton, New York 11973, USA
| | - R Sinclair
- Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37996, USA
| | - M T McDonnell
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - R Yu
- Condensed Matter Physics and Materials Science Division, Brookhaven National Laboratory, Upton, New York 11973, USA
| | - M Abeykoon
- Photon Sciences Division, Brookhaven National Laboratory, Upton, New York 11973, USA
| | - M G Tucker
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - A M Tsvelik
- Condensed Matter Physics and Materials Science Division, Brookhaven National Laboratory, Upton, New York 11973, USA
| | - S J L Billinge
- Condensed Matter Physics and Materials Science Division, Brookhaven National Laboratory, Upton, New York 11973, USA
- Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027, USA
| | - H D Zhou
- Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37996, USA
| | - W-G Yin
- Condensed Matter Physics and Materials Science Division, Brookhaven National Laboratory, Upton, New York 11973, USA
| | - E S Bozin
- Condensed Matter Physics and Materials Science Division, Brookhaven National Laboratory, Upton, New York 11973, USA
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28
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Ahn J, Nagaosa N. Theory of optical responses in clean multi-band superconductors. Nat Commun 2021; 12:1617. [PMID: 33712592 PMCID: PMC7954819 DOI: 10.1038/s41467-021-21905-x] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2020] [Accepted: 02/18/2021] [Indexed: 12/04/2022] Open
Abstract
Electromagnetic responses in superconductors provide valuable information on the pairing symmetry as well as physical quantities such as the superfluid density. However, at the superconducting gap energy scale, optical excitations of the Bogoliugov quasiparticles are forbidden in conventional Bardeen-Cooper-Schrieffer superconductors when momentum is conserved. Accordingly, far-infrared optical responses have been understood in the framework of a dirty-limit theory by Mattis and Bardeen for over 60 years. Here we show, by investigating the selection rules imposed by particle-hole symmetry and unitary symmetries, that intrinsic momentum-conserving optical excitations can occur in clean multi-band superconductors when one of the following three conditions is satisfied: (i) inversion symmetry breaking, (ii) symmetry protection of the Bogoliubov Fermi surfaces, or (iii) simply finite spin-orbit coupling with unbroken time reversal and inversion symmetries. This result indicates that clean-limit optical responses are common beyond the straightforward case of broken inversion symmetry. We apply our theory to optical responses in FeSe, a clean multi-band superconductor with inversion symmetry and significant spin-orbit coupling. This result paves the way for studying clean-limit superconductors through optical measurements.
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Affiliation(s)
- Junyeong Ahn
- Department of Physics, Harvard University, Cambridge, MA, USA.
- RIKEN Center for Emergent Matter Science (CEMS), Wako, Saitama, Japan.
| | - Naoto Nagaosa
- RIKEN Center for Emergent Matter Science (CEMS), Wako, Saitama, Japan.
- Department of Applied Physics, The University of Tokyo, Bunkyo, Tokyo, Japan.
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29
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Bu K, Zhang W, Fei Y, Zheng Y, Ai F, Wu Z, Wang Q, Wo H, Zhao J, Yin Y. Observation of an electronic order along [110] direction in FeSe. Nat Commun 2021; 12:1385. [PMID: 33654059 PMCID: PMC7925548 DOI: 10.1038/s41467-021-21318-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2019] [Accepted: 01/17/2021] [Indexed: 11/30/2022] Open
Abstract
Multiple ordered states have been observed in unconventional superconductors. Here, we apply scanning tunneling microscopy to probe the intrinsic ordered states in FeSe, the structurally simplest iron-based superconductor. Besides the well-known nematic order along [100] direction, we observe a checkerboard charge order in the iron lattice, which we name a [110] electronic order in FeSe. The [110] electronic order is robust at 77 K, accompanied with the rather weak [100] nematic order. At 4.5 K, The [100] nematic order is enhanced, while the [110] electronic order forms domains with reduced correlation length. In addition, the collective [110] order is gaped around [−40, 40] meV at 4.5 K. The observation of this exotic electronic order may shed new light on the origin of the ordered states in FeSe. Understanding the relation of different electronic orders in high temperature superconductors is of fundamental interest. Here, the authors observe a checkerboard charge order along [110] direction of FeSe.
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Affiliation(s)
- Kunliang Bu
- Zhejiang Province Key Laboratory of Quantum Technology and Device, Department of Physics, Zhejiang University, Hangzhou, China
| | - Wenhao Zhang
- Zhejiang Province Key Laboratory of Quantum Technology and Device, Department of Physics, Zhejiang University, Hangzhou, China
| | - Ying Fei
- Zhejiang Province Key Laboratory of Quantum Technology and Device, Department of Physics, Zhejiang University, Hangzhou, China
| | - Yuan Zheng
- Zhejiang Province Key Laboratory of Quantum Technology and Device, Department of Physics, Zhejiang University, Hangzhou, China
| | - Fangzhou Ai
- Zhejiang Province Key Laboratory of Quantum Technology and Device, Department of Physics, Zhejiang University, Hangzhou, China
| | - Zongxiu Wu
- Zhejiang Province Key Laboratory of Quantum Technology and Device, Department of Physics, Zhejiang University, Hangzhou, China
| | - Qisi Wang
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai, China
| | - Hongliang Wo
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai, China
| | - Jun Zhao
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai, China.,Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, China
| | - Yi Yin
- Zhejiang Province Key Laboratory of Quantum Technology and Device, Department of Physics, Zhejiang University, Hangzhou, China. .,Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, China.
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30
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Time-reversal symmetry breaking in the Fe-chalcogenide superconductors. Proc Natl Acad Sci U S A 2021; 118:2007241118. [PMID: 33436408 DOI: 10.1073/pnas.2007241118] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Topological superconductivity has been sought in a variety of heterostructure systems, the interest being that a material displaying such a phenomenon could prove to be the ideal platform to support Majorana fermions, which in turn could be the basis for advanced qubit technologies. Recently, the high-Tc family of superconductors, FeTe1-xSex, have been shown to exhibit the property of topological superconductivity and further, evidence has been found for the presence of Majorana fermions. We have studied the interplay of topology, magnetism, and superconductivity in the FeTe1-x Se x family using high-resolution laser-based photoemission. At the bulk superconducting transition, a gap opens at the chemical potential as expected. However, a second gap is observed to open at the Dirac point in the topological surface state. The associated mass acquisition in the topological state points to time-reversal symmetry breaking, probably associated with the formation of ferromagnetism in the surface layer. The presence of intrinsic ferromagnetism combined with strong spin-orbit coupling provides an ideal platform for a range of exotic topological phenomena.
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31
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Gu Q, Li Y, Wan S, Li H, Guo W, Yang H, Li Q, Zhu X, Pan X, Nie Y, Wen HH. Single particle tunneling spectrum of superconducting Nd 1-xSr xNiO 2 thin films. Nat Commun 2020; 11:6027. [PMID: 33247088 PMCID: PMC7695741 DOI: 10.1038/s41467-020-19908-1] [Citation(s) in RCA: 63] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2020] [Accepted: 11/03/2020] [Indexed: 11/08/2022] Open
Abstract
The pairing mechanism in cuprates remains as one of the most challenging issues in condensed matter physics. Recently, superconductivity was discovered in thin films of the infinite-layer nickelate Nd1-xSrxNiO2 (x = 0.12-0.25) which is believed to have the similar 3d9 orbital electrons as that in cuprates. Here we report single-particle tunneling measurements on the superconducting nickelate thin films. We find predominantly two types of tunneling spectra, one shows a V-shape feature which can be fitted well by a d-wave gap function with gap maximum of about 3.9 meV, another one exhibits a full gap of about 2.35 meV. Some spectra demonstrate mixed contributions of these two components. Combining with theoretical calculations, we attribute the d-wave gap to the pairing potential of the [Formula: see text] orbital. Several possible reasons are given for explaining the full gap feature. Our results indicate both similarities and distinctions between the newly found Ni-based superconductors and cuprates.
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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, Nanjing, China
| | - Yueying Li
- National Laboratory of Solid State Microstructures, Jiangsu Key Laboratory of Artificial Functional Materials, College of Engineering and Applied Sciences, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, 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, Nanjing, China
| | - Huazhou Li
- National Laboratory of Solid State Microstructures and Department of Physics, Center for Superconducting Physics and Materials, Collaborative Innovation Center for Advanced Microstructures, Nanjing University, Nanjing, China
| | - Wei Guo
- National Laboratory of Solid State Microstructures, Jiangsu Key Laboratory of Artificial Functional Materials, College of Engineering and Applied Sciences, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, 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, Nanjing, China
| | - Qing Li
- National Laboratory of Solid State Microstructures and Department of Physics, Center for Superconducting Physics and Materials, Collaborative Innovation Center for Advanced Microstructures, Nanjing University, Nanjing, China
| | - Xiyu Zhu
- National Laboratory of Solid State Microstructures and Department of Physics, Center for Superconducting Physics and Materials, Collaborative Innovation Center for Advanced Microstructures, Nanjing University, Nanjing, China
| | - Xiaoqing Pan
- Department of Materials Science and Engineering, Department of Physics and Astronomy, University of California, Irvine, CA, 92697, USA
| | - Yuefeng Nie
- National Laboratory of Solid State Microstructures, Jiangsu Key Laboratory of Artificial Functional Materials, College of Engineering and Applied Sciences, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, China.
| | - 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, Nanjing, China.
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Fanfarillo L, Valli A, Capone M. Synergy between Hund-Driven Correlations and Boson-Mediated Superconductivity. PHYSICAL REVIEW LETTERS 2020; 125:177001. [PMID: 33156687 DOI: 10.1103/physrevlett.125.177001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/02/2019] [Accepted: 09/17/2020] [Indexed: 06/11/2023]
Abstract
Multiorbital systems such as the iron-based superconductors provide a new avenue to attack the long-standing problem of superconductivity in strongly correlated systems. In this work we study the superconductivity driven by a generic bosonic mechanism in a multiorbital model including the full dynamical electronic correlations induced by the Hubbard U and the Hund's coupling. We show that superconductivity survives much more in a Hund's metal than in an ordinary correlated metal with the same degree of correlation. The redistribution of spectral weight characteristic of the Hund's metal reflects also in the enhancement of the orbital-selective character of the superconducting gaps, in agreement with experiments in iron-based superconductors.
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Affiliation(s)
- Laura Fanfarillo
- Scuola Internazionale Superiore di Studi Avanzati (SISSA) and CNR-IOM, Via Bonomea 265, 34136 Trieste, Italy
- Department of Physics, University of Florida, Gainesville, Florida 32611, USA
| | - Angelo Valli
- Scuola Internazionale Superiore di Studi Avanzati (SISSA) and CNR-IOM, Via Bonomea 265, 34136 Trieste, Italy
- Institute for Solid State Physics, Vienna University of Technology, 1040 Vienna, Austria
| | - Massimo Capone
- Scuola Internazionale Superiore di Studi Avanzati (SISSA) and CNR-IOM, Via Bonomea 265, 34136 Trieste, Italy
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Abstract
Emergent electronic phenomena in iron-based superconductors have been at the forefront of condensed matter physics for more than a decade. Much has been learned about the origins and intertwined roles of ordered phases, including nematicity, magnetism, and superconductivity, in this fascinating class of materials. In recent years, focus has been centered on the peculiar and highly unusual properties of FeSe and its close cousins. This family of materials has attracted considerable attention due to the discovery of unexpected superconducting gap structures, a wide range of superconducting critical temperatures, and evidence for nontrivial band topology, including associated spin-helical surface states and vortex-induced Majorana bound states. Here, we review superconductivity in iron chalcogenide superconductors, including bulk FeSe, doped bulk FeSe, FeTe1−xSex, intercalated FeSe materials, and monolayer FeSe and FeTe1−xSex on SrTiO3. We focus on the superconducting properties, including a survey of the relevant experimental studies, and a discussion of the different proposed theoretical pairing scenarios. In the last part of the paper, we review the growing recent evidence for nontrivial topological effects in FeSe-related materials, focusing again on interesting implications for superconductivity.
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Coleman P, Komijani Y, König EJ. Triplet Resonating Valence Bond State and Superconductivity in Hund's Metals. PHYSICAL REVIEW LETTERS 2020; 125:077001. [PMID: 32857586 DOI: 10.1103/physrevlett.125.077001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/03/2019] [Accepted: 06/24/2020] [Indexed: 06/11/2023]
Abstract
A central idea in strongly correlated systems is that doping a Mott insulator leads to a superconductor by transforming the resonating valence bonds (RVBs) into spin-singlet Cooper pairs. Here, we argue that a spin-triplet RVB (tRVB) state, driven by spatially, or orbitally anisotropic ferromagnetic interactions can provide the parent state for triplet superconductivity. We apply this idea to the iron-based superconductors, arguing that strong on site Hund's interactions develop intra-atomic tRVBs between the t_{2g} orbitals. On doping, the presence of two iron atoms per unit cell allows these interorbital triplets to coherently delocalize onto the Fermi surface, forming a fully gapped triplet superconductor. This mechanism gives rise to a unique staggered structure of on site pair correlations, detectable as an alternating π phase shift in a scanning Josephson tunneling microscope.
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Affiliation(s)
- Piers Coleman
- Center for Materials Theory, Department of Physics and Astronomy, Rutgers University, 136 Frelinghuysen Road, Piscataway, New Jersey 08854-8019, USA
- Department of Physics, Royal Holloway, University of London, Egham, Surrey TW20 0EX, United Kingdom
| | - Yashar Komijani
- Center for Materials Theory, Department of Physics and Astronomy, Rutgers University, 136 Frelinghuysen Road, Piscataway, New Jersey 08854-8019, USA
| | - Elio J König
- Center for Materials Theory, Department of Physics and Astronomy, Rutgers University, 136 Frelinghuysen Road, Piscataway, New Jersey 08854-8019, USA
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35
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Han TT, Chen L, Cai C, Wang YD, Wang ZG, Xin ZM, Zhang Y. Isostructural Spin-Density-Wave and Superconducting Gap Anisotropies in Iron-Arsenide Superconductors. PHYSICAL REVIEW LETTERS 2020; 124:247002. [PMID: 32639832 DOI: 10.1103/physrevlett.124.247002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/22/2020] [Accepted: 06/01/2020] [Indexed: 06/11/2023]
Abstract
When passing through a phase transition, electronic system saves energy by opening energy gaps at the Fermi level. Delineating the energy gap anisotropy provides insights into the origin of the interactions that drive the phase transition. Here, we report the angle-resolved photoemission spectroscopy (ARPES) study on the detailed gap anisotropies in both the tetragonal magnetic and superconducting phases in Sr_{1-x}Na_{x}Fe_{2}As_{2}. First, we found that the spin-density-wave (SDW) gap is strongly anisotropic in the tetragonal magnetic phase. The gap magnitude correlates with the orbital character of Fermi surface closely. Second, we found that the SDW gap anisotropy is isostructural to the superconducting gap anisotropy regarding to the angular dependence, gap minima locations, and relative gap magnitudes. Our results indicate that the superconducting pairing interaction and magnetic interaction share the same origin. The intraorbital scattering plays an important role in constructing these interactions resulting in the orbital-selective magnetism and superconductivity in iron-based superconductors.
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Affiliation(s)
- T T Han
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
| | - L Chen
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
| | - C Cai
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
| | - Y D Wang
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
| | - Z G Wang
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
| | - Z M Xin
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
| | - Y Zhang
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
- Collaborative Innovation Center of Quantum Matter, Beijing 100871, China
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36
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Udina M, Grilli M, Benfatto L, Chubukov AV. Raman Response in the Nematic Phase of FeSe. PHYSICAL REVIEW LETTERS 2020; 124:197602. [PMID: 32469539 DOI: 10.1103/physrevlett.124.197602] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/29/2019] [Revised: 01/21/2020] [Accepted: 04/21/2020] [Indexed: 06/11/2023]
Abstract
Raman experiments on bulk FeSe revealed that the low-frequency part of the B_{1g} Raman response R_{B1g}(Ω), which probes nematic fluctuations, rapidly decreases below the nematic transition at T_{n}∼85 K. Such behavior is expected when a gap opens up and at a first glance is inconsistent with the fact that FeSe remains a metal below T_{n}. We argue that the drop of R_{B1g}(Ω) can be ascribed to the fact that the nematic order drastically changes the orbital content of low-energy excitations near hole and electron pockets, making them nearly mono-orbital. In this situation, the B_{1g} Raman response gets reduced by the same vertex corrections that enforce charge conservation in the symmetric Raman channel. The reduction holds at low frequencies and gives rise to gaplike behavior of R_{B1g}(Ω). We also show that the enhancement of the B_{1g} Raman response near T_{n} is consistent with the sign change of the nematic order parameter between hole and electron pockets.
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Affiliation(s)
- Mattia Udina
- Department of Physics and ISC-CNR, "Sapienza" University of Rome, P.le A. Moro 5, 00185 Rome, Italy
| | - Marco Grilli
- Department of Physics and ISC-CNR, "Sapienza" University of Rome, P.le A. Moro 5, 00185 Rome, Italy
| | - Lara Benfatto
- Department of Physics and ISC-CNR, "Sapienza" University of Rome, P.le A. Moro 5, 00185 Rome, Italy
| | - Andrey V Chubukov
- School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota 55455, USA
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37
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Song SY, Martiny JHJ, Kreisel A, Andersen BM, Seo J. Visualization of Local Magnetic Moments Emerging from Impurities in Hund's Metal States of FeSe. PHYSICAL REVIEW LETTERS 2020; 124:117001. [PMID: 32242691 DOI: 10.1103/physrevlett.124.117001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/23/2019] [Revised: 09/30/2019] [Accepted: 02/21/2020] [Indexed: 06/11/2023]
Abstract
Understanding the origin of the magnetism of high temperature superconductors is crucial for establishing their unconventional pairing mechanism. Recently, theory predicts that FeSe is close to a magnetic quantum critical point, and thus weak perturbations such as impurities could induce local magnetic moments. To elucidate such quantum instability, we have employed scanning tunneling microscopy and spectroscopy. In particular, we have grown FeSe film on superconducting Pb(111) using molecular beam epitaxy and investigated magnetic excitation caused by impurities in the proximity-induced superconducting gap of FeSe. Our study provides deep insight into the origin of the magnetic ordering of FeSe by showing the way local magnetic moments develop in response to impurities near the magnetic quantum critical point.
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Affiliation(s)
- Sang Yong Song
- Department of Emerging Materials Science, DGIST, 333 Techno-Jungang-daero, Hyeonpung-Eup, Dalseong-Gun, Daegu 42988, Korea
| | - J H J Martiny
- Center for Nanostructured Graphene (CNG), Department of Physics, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark
| | - A Kreisel
- Institut für Theoretische Physik, Universität Leipzig, D-04103 Leipzig, Germany
| | - B M Andersen
- Niels Bohr Institute, University of Copenhagen, Lyngbyvej 2, DK-2100 Copenhagen, Denmark
| | - Jungpil Seo
- Department of Emerging Materials Science, DGIST, 333 Techno-Jungang-daero, Hyeonpung-Eup, Dalseong-Gun, Daegu 42988, Korea
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38
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Kasahara S, Sato Y, Licciardello S, Čulo M, Arsenijević S, Ottenbros T, Tominaga T, Böker J, Eremin I, Shibauchi T, Wosnitza J, Hussey NE, Matsuda Y. Evidence for an Fulde-Ferrell-Larkin-Ovchinnikov State with Segmented Vortices in the BCS-BEC-Crossover Superconductor FeSe. PHYSICAL REVIEW LETTERS 2020; 124:107001. [PMID: 32216412 DOI: 10.1103/physrevlett.124.107001] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/19/2019] [Accepted: 02/05/2020] [Indexed: 06/10/2023]
Abstract
We present resistivity and thermal-conductivity measurements of superconducting FeSe in intense magnetic fields up to 35 T applied parallel to the ab plane. At low temperatures, the upper critical field μ_{0}H_{c2}^{ab} shows an anomalous upturn, while thermal conductivity exhibits a discontinuous jump at μ_{0}H^{*}≈24 T well below μ_{0}H_{c2}^{ab}, indicating a first-order phase transition in the superconducting state. This demonstrates the emergence of a distinct field-induced superconducting phase. Moreover, the broad resistive transition at high temperatures abruptly becomes sharp upon entering the high-field phase, indicating a dramatic change of the magnetic-flux properties. We attribute the high-field phase to the Fulde-Ferrel-Larkin-Ovchinnikov (FFLO) state, where the formation of planar nodes gives rise to a segmentation of the flux-line lattice. We point out that strongly orbital-dependent pairing as well as spin-orbit interactions, the multiband nature, and the extremely small Fermi energy are important for the formation of the FFLO state in FeSe.
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Affiliation(s)
- S Kasahara
- Department of Physics, Kyoto University, Kyoto 606-8502 Japan
| | - Y Sato
- Department of Physics, Kyoto University, Kyoto 606-8502 Japan
| | - S Licciardello
- High Field Magnet Laboratory (HFML-EMFL) and Institute for Molecules and Materials, Radboud University, 6525 ED Nijmegen, The Netherlands
| | - M Čulo
- High Field Magnet Laboratory (HFML-EMFL) and Institute for Molecules and Materials, Radboud University, 6525 ED Nijmegen, The Netherlands
| | - S Arsenijević
- Hochfeld-Magnetlabor Dresden (HLD-EMFL) and Würzburg-Dresden Cluster of Excellence ct.qmat, Helmholtz-Zentrum Dresden-Rossendorf, D-01328 Dresden, Germany
| | - T Ottenbros
- High Field Magnet Laboratory (HFML-EMFL) and Institute for Molecules and Materials, Radboud University, 6525 ED Nijmegen, The Netherlands
| | - T Tominaga
- Department of Physics, Kyoto University, Kyoto 606-8502 Japan
| | - J Böker
- Institut für Theoretische Physik III, Ruhr-Universität Bochum, D-44801 Bochum, Germany
| | - I Eremin
- Institut für Theoretische Physik III, Ruhr-Universität Bochum, D-44801 Bochum, Germany
- National University of Science and Technology MISiS, 119049 Moscow, Russian Federation
| | - T Shibauchi
- Department of Advanced Materials Science, University of Tokyo, Chiba 277-8561, Japan
| | - J Wosnitza
- Hochfeld-Magnetlabor Dresden (HLD-EMFL) and Würzburg-Dresden Cluster of Excellence ct.qmat, Helmholtz-Zentrum Dresden-Rossendorf, D-01328 Dresden, Germany
- Institut für Festkörper- und Materialphysik, Technische Universität Dresden, 01062 Dresden, Germany
| | - N E Hussey
- High Field Magnet Laboratory (HFML-EMFL) and Institute for Molecules and Materials, Radboud University, 6525 ED Nijmegen, The Netherlands
- H.H. Wills Physics Laboratory, University of Bristol, Tyndall Avenue, BS8 1TL, United Kingdom
| | - Y Matsuda
- Department of Physics, Kyoto University, Kyoto 606-8502 Japan
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39
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Chen C, Liu C, Liu Y, Wang J. Bosonic Mode and Impurity-Scattering in Monolayer Fe(Te,Se) High-Temperature Superconductors. NANO LETTERS 2020; 20:2056-2061. [PMID: 32045257 DOI: 10.1021/acs.nanolett.0c00028] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
The electron pairing mechanism has always been one of the most challenging problems in high-temperature superconductors. Fe(Te,Se), as the superconductor with intrinsic topological property, may host Majorana bound states and has attracted tremendous interest. While in bulk Fe(Te,Se) the pairing mechanism has been experimentally investigated, it remains little understood in its two-dimensional limit counterpart. Here, by in situ scanning tunneling spectroscopy, we show clear evidence of the bosonic mode Ω beyond the superconducting gap Δ in monolayer FeTe0.5Se0.5/SrTiO3(001) high-temperature superconductor. Statistically, Ω shows an obvious anticorrelation with Δ and appears below 2Δ, consistent with the spin-excitation nature. Furthermore, the in-gap bound states induced by two types of magnetically different impurities support the sign-reversing pairing scenario. Our results not only suggest that the spin-excitation-like bosonic mode within a sign-reversing pairing plays an essential role in monolayer FeTe0.5Se0.5/SrTiO3(001) but also offer the crucial information for investigating the high-temperature superconductivity in interfacial iron selenides.
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Affiliation(s)
- Cheng Chen
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, P.R. China
| | - Chaofei Liu
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, P.R. China
| | - Yi Liu
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, P.R. China
| | - Jian Wang
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, P.R. China
- Collaborative Innovation Center of Quantum Matter, Beijing 100871, P.R. China
- CAS Center for Excellence in Topological Quantum Computation, University of Chinese Academy of Sciences, Beijing 100190, P.R. China
- Beijing Academy of Quantum Information Sciences, Beijing 100193, P.R. China
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40
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Sharma R, Edkins SD, Wang Z, Kostin A, Sow C, Maeno Y, Mackenzie AP, Davis JCS, Madhavan V. Momentum-resolved superconducting energy gaps of Sr 2RuO 4 from quasiparticle interference imaging. Proc Natl Acad Sci U S A 2020; 117:5222-5227. [PMID: 32094178 PMCID: PMC7071898 DOI: 10.1073/pnas.1916463117] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Sr2RuO4 has long been the focus of intense research interest because of conjectures that it is a correlated topological superconductor. It is the momentum space (k-space) structure of the superconducting energy gap [Formula: see text] on each band i that encodes its unknown superconducting order parameter. However, because the energy scales are so low, it has never been possible to directly measure the [Formula: see text] of Sr2RuO4 Here, we implement Bogoliubov quasiparticle interference (BQPI) imaging, a technique capable of high-precision measurement of multiband [Formula: see text] At T = 90 mK, we visualize a set of Bogoliubov scattering interference wavevectors [Formula: see text] consistent with eight gap nodes/minima that are all closely aligned to the [Formula: see text] crystal lattice directions on both the α and β bands. Taking these observations in combination with other very recent advances in directional thermal conductivity [E. Hassinger et al., Phys. Rev. X 7, 011032 (2017)], temperature-dependent Knight shift [A. Pustogow et al., Nature 574, 72-75 (2019)], time-reversal symmetry conservation [S. Kashiwaya et al., Phys. Rev B, 100, 094530 (2019)], and theory [A. T. Rømer et al., Phys. Rev. Lett. 123, 247001 (2019); H. S. Roising, T. Scaffidi, F. Flicker, G. F. Lange, S. H. Simon, Phys. Rev. Res. 1, 033108 (2019); and O. Gingras, R. Nourafkan, A. S. Tremblay, M. Côté, Phys. Rev. Lett. 123, 217005 (2019)], the BQPI signature of Sr2RuO4 appears most consistent with [Formula: see text] having [Formula: see text] [Formula: see text] symmetry.
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Affiliation(s)
- Rahul Sharma
- Laboratory of Atomic and Solid State Physics, Department of Physics, Cornell University, Ithaca, NY 14853
- Condensed Matter Physics and Material Science Department, Brookhaven National Laboratory, Upton, NY 11973
| | - Stephen D Edkins
- Department of Applied Physics, Stanford University, Stanford, CA 94305
| | - Zhenyu Wang
- Department of Physics, University of Illinois, Urbana, IL 61801
| | - Andrey Kostin
- Laboratory of Atomic and Solid State Physics, Department of Physics, Cornell University, Ithaca, NY 14853
- Condensed Matter Physics and Material Science Department, Brookhaven National Laboratory, Upton, NY 11973
| | - Chanchal Sow
- Department of Physics, Kyoto University, 606-8502 Kyoto, Japan
- Department of Physics, Indian Institute of Technology-Kanpur, 208016 Uttar Pradesh, India
| | - Yoshiteru Maeno
- Department of Physics, Kyoto University, 606-8502 Kyoto, Japan
| | - Andrew P Mackenzie
- Physics of Quantum Materials Department, Max Planck Institute for Chemical Physics of Solids, D-01187 Dresden, Germany
- School of Physics and Astronomy, University of St. Andrews, North Haugh, St. Andrews KY16 9SS, United Kingdom
| | - J C Séamus Davis
- Laboratory of Atomic and Solid State Physics, Department of Physics, Cornell University, Ithaca, NY 14853;
- Physics of Quantum Materials Department, Max Planck Institute for Chemical Physics of Solids, D-01187 Dresden, Germany
- Clarendon Laboratory, University of Oxford, Oxford OX1 3PU, United Kingdom
- Department of Physics, University College Cork, T12R5C Cork, Ireland
| | - Vidya Madhavan
- Department of Physics, University of Illinois, Urbana, IL 61801;
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41
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Cheung SC, Shin JY, Lau Y, Chen Z, Sun J, Zhang Y, Müller MA, Eremin IM, Wright JN, Pasupathy AN. Dictionary learning in Fourier-transform scanning tunneling spectroscopy. Nat Commun 2020; 11:1081. [PMID: 32102995 PMCID: PMC7044214 DOI: 10.1038/s41467-020-14633-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2017] [Accepted: 01/17/2020] [Indexed: 11/15/2022] Open
Abstract
Modern high-resolution microscopes are commonly used to study specimens that have dense and aperiodic spatial structure. Extracting meaningful information from images obtained from such microscopes remains a formidable challenge. Fourier analysis is commonly used to analyze the structure of such images. However, the Fourier transform fundamentally suffers from severe phase noise when applied to aperiodic images. Here, we report the development of an algorithm based on nonconvex optimization that directly uncovers the fundamental motifs present in a real-space image. Apart from being quantitatively superior to traditional Fourier analysis, we show that this algorithm also uncovers phase sensitive information about the underlying motif structure. We demonstrate its usefulness by studying scanning tunneling microscopy images of a Co-doped iron arsenide superconductor and prove that the application of the algorithm allows for the complete recovery of quasiparticle interference in this material. Aperiodic structure imaging suffers limitations when utilizing Fourier analysis. The authors report an algorithm that quantitatively overcomes these limitations based on nonconvex optimization, demonstrated by studying aperiodic structures via the phase sensitive interference in STM images.
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Affiliation(s)
- Sky C Cheung
- Department of Physics, Columbia University, New York, NY, 10027, USA
| | - John Y Shin
- Department of Physics, Columbia University, New York, NY, 10027, USA
| | - Yenson Lau
- Department of Electrical Engineering, Columbia University, New York, NY, 10027, USA
| | - Zhengyu Chen
- Department of Electrical Engineering, Columbia University, New York, NY, 10027, USA
| | - Ju Sun
- Department of Electrical Engineering, Columbia University, New York, NY, 10027, USA
| | - Yuqian Zhang
- Department of Electrical Engineering, Columbia University, New York, NY, 10027, USA
| | - Marvin A Müller
- Institut für Theoretische Physik III, Ruhr-Universität Bochum, 44801, Bochum, Germany
| | - Ilya M Eremin
- Institut für Theoretische Physik III, Ruhr-Universität Bochum, 44801, Bochum, Germany.,National University of Science and Technology MISiS, 119049, Moscow, Russian Federation
| | - John N Wright
- Department of Electrical Engineering, Columbia University, New York, NY, 10027, USA.
| | - Abhay N Pasupathy
- Department of Physics, Columbia University, New York, NY, 10027, USA.
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42
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Topological ultranodal pair states in iron-based superconductors. Nat Commun 2020; 11:523. [PMID: 31988317 PMCID: PMC6985224 DOI: 10.1038/s41467-020-14357-2] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2019] [Accepted: 12/19/2019] [Indexed: 11/09/2022] Open
Abstract
Bogoliubov Fermi surfaces are contours of zero-energy excitations that are protected in the superconducting state. Here we show that multiband superconductors with dominant spin singlet, intraband pairing of spin-1/2 electrons can undergo a transition to a state with Bogoliubov Fermi surfaces if spin-orbit coupling, interband pairing and time reversal symmetry breaking are also present. These latter effects may be small, but drive the transition to the topological state for appropriate nodal structure of the intra-band pair. Such a state should display nonzero zero-bias density of states and corresponding residual Sommerfeld coefficient as for a disordered nodal superconductor, but occurring even in the pure case. We present a model appropriate for iron-based superconductors where the topological transition associated with creation of a Bogoliubov Fermi surface can be studied. The model gives results that strongly resemble experiments on FeSe1−xSx across the nematic transition, where this ultranodal behavior may already have been observed. Experiments indicate an abrupt change in the pairing gap near the nematic transition in the FeSe1−xSx iron-based superconductor. Here, Setty et al. propose to explain them via a novel spin-1/2 paired state with topologically protected zero-energy excitations over a finite area nodal surface.
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43
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Chen T, Chen Y, Tam DW, Gao B, Qiu Y, Schneidewind A, Radelytskyi I, Prokes K, Chi S, Matsuda M, Broholm C, Dai P. Anisotropic effect of a magnetic field on the neutron spin resonance in FeSe. PHYSICAL REVIEW. B 2020; 101:10.1103/physrevb.101.140504. [PMID: 33655092 PMCID: PMC7918269 DOI: 10.1103/physrevb.101.140504] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
We use inelastic neutron scattering to study the effect of a magnetic field on the neutron spin resonance (E r = 3.6 meV) of superconducting FeSe (T c = 9 K). While a field aligned along the in-plane direction broadens and suppresses the resonance, a c-axis aligned field does so much more efficiently, consistent with the anisotropic field-induced suppression of the superfluid density from the heat capacity measurements. These results suggest that the resonance in FeSe is associated with the superconducting electrons arising from orbital selective quasiparticle excitations between the hole and electron Fermi surfaces.
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Affiliation(s)
- Tong Chen
- Department of Physics and Astronomy, Rice University, Houston, Texas 77005, USA
| | - Youzhe Chen
- Department of Physics and Astronomy, Johns Hopkins University, Baltimore, Maryland 21218, USA
| | - David W. Tam
- Department of Physics and Astronomy, Rice University, Houston, Texas 77005, USA
| | - Bin Gao
- Department of Physics and Astronomy, Rice University, Houston, Texas 77005, USA
| | - Yiming Qiu
- NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA
| | - Astrid Schneidewind
- Jülich Center for Neutron Sciences, Forschungszentrum Jülich GmbH, Outstation at MLZ, D-85747 Garching, Germany
| | - Igor Radelytskyi
- Jülich Center for Neutron Sciences, Forschungszentrum Jülich GmbH, Outstation at MLZ, D-85747 Garching, Germany
| | - Karel Prokes
- Helmholtz Zentrum Berlin für Materialien und Energie, 14109 Berlin, Germany
| | - Songxue Chi
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - Masaaki Matsuda
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - Collin Broholm
- Department of Physics and Astronomy, Johns Hopkins University, Baltimore, Maryland 21218, USA
- NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA
| | - Pengcheng Dai
- Department of Physics and Astronomy, Rice University, Houston, Texas 77005, USA
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44
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Rømer AT, Scherer DD, Eremin IM, Hirschfeld PJ, Andersen BM. Knight Shift and Leading Superconducting Instability from Spin Fluctuations in Sr_{2}RuO_{4}. PHYSICAL REVIEW LETTERS 2019; 123:247001. [PMID: 31922834 DOI: 10.1103/physrevlett.123.247001] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/15/2019] [Indexed: 06/10/2023]
Abstract
Recent nuclear magnetic resonance studies [A. Pustogow et al., Nature 574, 72 (2019)] have challenged the prevalent chiral triplet pairing scenario proposed for Sr_{2}RuO_{4}. To provide guidance from microscopic theory as to which other pair states might be compatible with the new data, we perform a detailed theoretical study of spin fluctuation mediated pairing for this compound. We map out the phase diagram as a function of spin-orbit coupling, interaction parameters, and band structure properties over physically reasonable ranges, comparing when possible with photoemission and inelastic neutron scattering data information. We find that even-parity pseudospin singlet solutions dominate large regions of the phase diagram, but in certain regimes spin-orbit coupling favors a near-nodal odd-parity triplet superconducting state, which is either helical or chiral depending on the proximity of the γ band to the van Hove points. A surprising near degeneracy of the nodal s^{'} and d_{x^{2}-y^{2}} wave solutions leads to the possibility of a near-nodal time-reversal symmetry broken s^{'}+id_{x^{2}-y^{2}} pair state. Predictions for the temperature dependence of the Knight shift for fields in and out of plane are presented for all states.
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Affiliation(s)
- A T Rømer
- Niels Bohr Institute, University of Copenhagen, Vibenhuset, Lyngbyvej 2, DK-2100 Copenhagen, Denmark
- Institut Laue-Langevin, 71 avenue des Martyrs CS 20156, 38042 Grenoble Cedex 9, France
| | - D D Scherer
- Niels Bohr Institute, University of Copenhagen, Vibenhuset, Lyngbyvej 2, DK-2100 Copenhagen, Denmark
| | - I M Eremin
- Institut für Theoretische Physik III, Ruhr-Universität Bochum, D-44801 Bochum, Germany
- National University of Science and Technology MISiS, 119049 Moscow, Russia
| | - P J Hirschfeld
- Department of Physics, University of Florida, Gainesville, Florida 32611, USA
| | - B M Andersen
- Niels Bohr Institute, University of Copenhagen, Vibenhuset, Lyngbyvej 2, DK-2100 Copenhagen, Denmark
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45
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Kwon J, Jun SW, Choi SI, Mao X, Kim J, Koh EK, Kim YH, Kim SK, Hwang DY, Kim CS, Lee J. FeSe quantum dots for in vivo multiphoton biomedical imaging. SCIENCE ADVANCES 2019; 5:eaay0044. [PMID: 31840070 PMCID: PMC6897543 DOI: 10.1126/sciadv.aay0044] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/12/2019] [Accepted: 09/20/2019] [Indexed: 06/02/2023]
Abstract
An immense demand in biomedical imaging is to develop efficient photoluminescent probes with high biocompatibility and quantum yield, as well as multiphoton absorption performance to improve penetration depth and spatial resolution. Here, iron selenide (FeSe) quantum dots (QDs) are reported to meet these criteria. The synthesized QDs exhibit two- and three-photon excitation property at 800- and 1080-nm wavelengths and high quantum yield (ca. 40%), which are suitable for second-window imaging. To verify their biosuitability, poly(ethylene glycol)-conjugated QDs were linked with human epidermal growth factor receptor 2 (HER2) antibodies for in vitro/in vivo two-photon imaging in HER2-overexpressed MCF7 cells and a xenograft breast tumor model in mice. Imaging was successfully carried out at a depth of up to 500 μm from the skin using a nonlinear femtosecond laser at an excitation wavelength of 800 nm. These findings may open up a way to apply biocompatible FeSe QDs to multiphoton cancer imaging.
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Affiliation(s)
- J. Kwon
- Department of Cogno-Mechatronics Engineering, Pusan National University, Busan 46240, Republic of Korea
| | - S. W. Jun
- Department of Cogno-Mechatronics Engineering, Pusan National University, Busan 46240, Republic of Korea
| | - S. I. Choi
- Division of Convergence Technology, National Cancer Center, Goyang 10408, Republic of Korea
| | - X. Mao
- College of Biomedical Engineering, Chongqing Medical University, Chongqing 400016, China
| | - J. Kim
- Department of Chemistry, Chungnam National University, Daejeon 34134, Republic of Korea
| | - E. K. Koh
- Department of Biomaterial Science, Pusan National University, Miryang 50463, Republic of Korea
| | - Y.-H. Kim
- Division of Convergence Technology, National Cancer Center, Goyang 10408, Republic of Korea
| | - S.-K. Kim
- Division of Convergence Technology, National Cancer Center, Goyang 10408, Republic of Korea
| | - D. Y. Hwang
- Department of Biomaterial Science, Pusan National University, Miryang 50463, Republic of Korea
| | - C.-S. Kim
- Department of Cogno-Mechatronics Engineering, Pusan National University, Busan 46240, Republic of Korea
| | - J. Lee
- Department of Chemistry, Chungnam National University, Daejeon 34134, Republic of Korea
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46
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Rhodes LC, Watson MD, Kim TK, Eschrig M. k_{z} Selective Scattering within Quasiparticle Interference Measurements of FeSe. PHYSICAL REVIEW LETTERS 2019; 123:216404. [PMID: 31809140 DOI: 10.1103/physrevlett.123.216404] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/05/2019] [Revised: 09/09/2019] [Indexed: 06/10/2023]
Abstract
Quasiparticle interference (QPI) provides a wealth of information relating to the electronic structure of a material. However, it is often assumed that this information is constrained to two-dimensional electronic states. We show that this is not necessarily the case. For FeSe, a system dominated by surface defects, we show that it is actually all electronic states with negligible group velocity in the z axis that are contained within the experimental data. By using a three-dimensional tight-binding model of FeSe, fit to photoemission measurements, we directly reproduce the experimental QPI scattering dispersion, within a T-matrix formalism, by including both k_{z}=0 and k_{z}=π electronic states. This result unifies both tunnelling based and photoemission based experiments on FeSe and highlights the importance of k_{z} within surface sensitive measurements of QPI.
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Affiliation(s)
- Luke C Rhodes
- Department of Physics, Royal Holloway, University of London, Egham, Surrey TW20 0EX, United Kingdom
- Diamond Light Source, Harwell Campus, Didcot OX11 0DE, United Kingdom
- School of Physics and Astronomy, University of St. Andrews, St. Andrews KY16 9SS, United Kingdom
| | - Matthew D Watson
- School of Physics and Astronomy, University of St. Andrews, St. Andrews KY16 9SS, United Kingdom
| | - Timur K Kim
- Diamond Light Source, Harwell Campus, Didcot OX11 0DE, United Kingdom
| | - Matthias Eschrig
- Department of Physics, Royal Holloway, University of London, Egham, Surrey TW20 0EX, United Kingdom
- Institute of Physics, University of Greifswald, Felix-Hausdorff-Strasse 6, 17489 Greifswald, Germany
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47
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Huang Y, Hu Y, Hu F, Yang R, Li C, Armstrong JN, Ren S. Correlation at two-dimensional charge-transfer FeSe interface. Chem Commun (Camb) 2019; 55:12643-12646. [PMID: 31580340 DOI: 10.1039/c9cc06163k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The charge transfer and spin coupling effects are explored at the interface of two-dimensional (2D) superconducting FeSe nanosheets and molecular photochromic potassium-7,7,8,8-tetracyanoquinodimethane (KTCNQ). Light-induced conductivity in 2D FeSe nanosheets is enhanced by the electron doping from KTCNQ by the destabilized spin-Peierls phase through their interface. Furthermore, the spin coupling at the interface of FeSe and KTCNQ shifts the dimerization transition temperature of KTCNQ. Our results suggest 2D exfoliated FeSe nanosheets as a versatile strongly correlated platform for the study of interfacial electron doping and spin coupling.
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Affiliation(s)
- Yulong Huang
- Department of Mechanical and Aerospace Engineering, Research and Education in Energy Environment & Water (RENEW) Institute, University at Buffalo, The State University of New York, Buffalo, NY 14260, USA.
| | - Yong Hu
- Department of Mechanical and Aerospace Engineering, Research and Education in Energy Environment & Water (RENEW) Institute, University at Buffalo, The State University of New York, Buffalo, NY 14260, USA.
| | - Feng Hu
- Department of Mechanical and Aerospace Engineering, Research and Education in Energy Environment & Water (RENEW) Institute, University at Buffalo, The State University of New York, Buffalo, NY 14260, USA.
| | - Ruizhe Yang
- Department of Mechanical and Aerospace Engineering, Research and Education in Energy Environment & Water (RENEW) Institute, University at Buffalo, The State University of New York, Buffalo, NY 14260, USA.
| | - Changning Li
- Department of Mechanical and Aerospace Engineering, Research and Education in Energy Environment & Water (RENEW) Institute, University at Buffalo, The State University of New York, Buffalo, NY 14260, USA.
| | - Jason N Armstrong
- Department of Mechanical and Aerospace Engineering, Research and Education in Energy Environment & Water (RENEW) Institute, University at Buffalo, The State University of New York, Buffalo, NY 14260, USA.
| | - Shenqiang Ren
- Department of Mechanical and Aerospace Engineering, Research and Education in Energy Environment & Water (RENEW) Institute, University at Buffalo, The State University of New York, Buffalo, NY 14260, USA.
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48
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Song C, Li X, Jiang Y, Wang X, Yao J, Meng S, Zhang J. Real-Space Imaging of Orbital Selectivity on SrTiO 3(001) Surface. ACS APPLIED MATERIALS & INTERFACES 2019; 11:37279-37284. [PMID: 31529959 DOI: 10.1021/acsami.9b11724] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Real-space access of the orbital degree of freedom in complex oxides is still challenging due to intricate electronic hybridization. Here, we report a direct observation of reproducible orbital-selective tunneling on a novel SrTiO3(001) surface by scanning tunneling microscopy. The electronic structures reversibly switch between two different sets of symmetries depending on the sample bias, which is accompanied by a remarkable change in energy-dependent spectroscopy data. Tunneling spectrum combined with density functional theory calculations elucidates that symmetry-breaking at the surface determines the crystal-splitting field of eg/t2g orbitals with a strong in-plane anisotropy so that electrons alternatingly fill eg and t2g orbitals during the imaging process with different biases. This surface superstructure provides a new strategy toward understanding orbital textures and orbital selectivity in complex oxides.
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Affiliation(s)
- Chuangye Song
- Department of Physics , Beijing Normal University , Beijing 100875 , China
| | - Xuanyi Li
- Institute of Physics , Chinese Academic of Science , Beijing 100190 , China
- School of Physics , University of Chinese Academy of Sciences , Beijing 100049 , China
| | - Ying Jiang
- International Center for Quantum Materials, School of Physics , Peking University , Beijing 100871 , China
| | - Xi Wang
- Key Laboratory of Luminescence and Optical Information, Ministry of Education, Department of Physics, School of Science , Beijing Jiaotong University , Beijing 100044 , China
- Chemistry and Chemical Engineering Guangdong Laboratory , Shantou 515031 , China
| | - Jiannian Yao
- Chemistry and Chemical Engineering Guangdong Laboratory , Shantou 515031 , China
- Key Laboratory of Photochemistry, Institute of Chemistry , Chinese Academy of Science , Beijing 100190 , China
| | - Sheng Meng
- Institute of Physics , Chinese Academic of Science , Beijing 100190 , China
- School of Physics , University of Chinese Academy of Sciences , Beijing 100049 , China
| | - Jinxing Zhang
- Department of Physics , Beijing Normal University , Beijing 100875 , China
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49
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Singh G, Jouan A, Herranz G, Scigaj M, Sánchez F, Benfatto L, Caprara S, Grilli M, Saiz G, Couëdo F, Feuillet-Palma C, Lesueur J, Bergeal N. Gap suppression at a Lifshitz transition in a multi-condensate superconductor. NATURE MATERIALS 2019; 18:948-954. [PMID: 31086324 DOI: 10.1038/s41563-019-0354-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/12/2018] [Accepted: 03/21/2019] [Indexed: 06/09/2023]
Abstract
In multi-orbital materials, superconductivity can exhibit several coupled condensates. In this context, quantum confinement in two-dimensional superconducting oxide interfaces offers new degrees of freedom to engineer the band structure and selectively control the occupancy of 3d orbitals by electrostatic doping. Here, we use resonant microwave transport to extract the superfluid stiffness of the (110)-oriented LaAlO3/SrTiO3 interface in the entire phase diagram. We provide evidence of a transition from single-condensate to two-condensate superconductivity driven by continuous and reversible electrostatic doping, which we relate to the Lifshitz transition between 3d bands based on numerical simulations of the quantum well. We find that the superconducting gap is suppressed while the second band is populated, challenging Bardeen-Cooper-Schrieffer theory. We ascribe this behaviour to the existence of superconducting order parameters with opposite signs in the two condensates due to repulsive coupling. Our findings offer an innovative perspective on the possibility to tune and control multiple-orbital physics in superconducting interfaces.
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Affiliation(s)
- G Singh
- Laboratoire de Physique et d'Etude des Matériaux, ESPCI Paris, PSL Research University, CNRS, Paris, France
- Université Pierre and Marie Curie, Sorbonne-Université, Paris, France
| | - A Jouan
- Laboratoire de Physique et d'Etude des Matériaux, ESPCI Paris, PSL Research University, CNRS, Paris, France
- Université Pierre and Marie Curie, Sorbonne-Université, Paris, France
| | - G Herranz
- Institut de Ciéncia de Materials de Barcelona (ICMAB-CSIC), Campus de la UAB, Bellaterra, Catalonia, Spain
| | - M Scigaj
- Institut de Ciéncia de Materials de Barcelona (ICMAB-CSIC), Campus de la UAB, Bellaterra, Catalonia, Spain
| | - F Sánchez
- Institut de Ciéncia de Materials de Barcelona (ICMAB-CSIC), Campus de la UAB, Bellaterra, Catalonia, Spain
| | - L Benfatto
- Institute for Complex Systems (ISC-CNR), UOS Sapienza, Roma, Italy
- Dipartimento di Fisica Università di Roma 'La Sapienza', Roma, Italy
| | - S Caprara
- Institute for Complex Systems (ISC-CNR), UOS Sapienza, Roma, Italy
- Dipartimento di Fisica Università di Roma 'La Sapienza', Roma, Italy
| | - M Grilli
- Institute for Complex Systems (ISC-CNR), UOS Sapienza, Roma, Italy
- Dipartimento di Fisica Università di Roma 'La Sapienza', Roma, Italy
| | - G Saiz
- Laboratoire de Physique et d'Etude des Matériaux, ESPCI Paris, PSL Research University, CNRS, Paris, France
- Université Pierre and Marie Curie, Sorbonne-Université, Paris, France
| | - F Couëdo
- Laboratoire de Physique et d'Etude des Matériaux, ESPCI Paris, PSL Research University, CNRS, Paris, France
- Université Pierre and Marie Curie, Sorbonne-Université, Paris, France
| | - C Feuillet-Palma
- Laboratoire de Physique et d'Etude des Matériaux, ESPCI Paris, PSL Research University, CNRS, Paris, France
- Université Pierre and Marie Curie, Sorbonne-Université, Paris, France
| | - J Lesueur
- Laboratoire de Physique et d'Etude des Matériaux, ESPCI Paris, PSL Research University, CNRS, Paris, France
- Université Pierre and Marie Curie, Sorbonne-Université, Paris, France
| | - N Bergeal
- Laboratoire de Physique et d'Etude des Matériaux, ESPCI Paris, PSL Research University, CNRS, Paris, France.
- Université Pierre and Marie Curie, Sorbonne-Université, Paris, France.
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50
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Bozin ES, Yin WG, Koch RJ, Abeykoon M, Hor YS, Zheng H, Lei HC, Petrovic C, Mitchell JF, Billinge SJL. Local orbital degeneracy lifting as a precursor to an orbital-selective Peierls transition. Nat Commun 2019; 10:3638. [PMID: 31409783 PMCID: PMC6692321 DOI: 10.1038/s41467-019-11372-w] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2019] [Accepted: 07/09/2019] [Indexed: 11/25/2022] Open
Abstract
Fundamental electronic principles underlying all transition metal compounds are the symmetry and filling of the d-electron orbitals and the influence of this filling on structural configurations and responses. Here we use a sensitive local structural technique, x-ray atomic pair distribution function analysis, to reveal the presence of fluctuating local-structural distortions at high temperature in one such compound, CuIr2S4. We show that this hitherto overlooked fluctuating symmetry-lowering is electronic in origin and will modify the energy-level spectrum and electronic and magnetic properties. The explanation is a local, fluctuating, orbital-degeneracy-lifted state. The natural extension of our result would be that this phenomenon is likely to be widespread amongst diverse classes of partially filled nominally degenerate d-electron systems, with potentially broad implications for our understanding of their properties. A common feature of many transition metal materials is global symmetry breaking at low temperatures. Here the authors show that such materials are characterized by fluctuating symmetry-lowering distortions that exist pre-formed in higher temperature phases with greater average symmetry.
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Affiliation(s)
- E S Bozin
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, NY, 11973, USA.
| | - W G Yin
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, NY, 11973, USA
| | - R J Koch
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, NY, 11973, USA
| | - M Abeykoon
- Photon Sciences Division, Brookhaven National Laboratory, Upton, NY, 11973, USA
| | - Y S Hor
- Materials Science Division, Argonne National Laboratory, Argonne, IL, 60439, USA.,Department of Physics, Missouri University of Science and Technology, Rolla, MO, 65409, USA
| | - H Zheng
- Materials Science Division, Argonne National Laboratory, Argonne, IL, 60439, USA
| | - H C Lei
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, NY, 11973, USA.,Department of Physics and Beijing Key Laboratory of Opto-electronic Functional Materials and Micro-nano Devices, Renmin University of China, 100872, Beijing, China
| | - C Petrovic
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, NY, 11973, USA
| | - J F Mitchell
- Materials Science Division, Argonne National Laboratory, Argonne, IL, 60439, USA
| | - S J L Billinge
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, NY, 11973, USA. .,Department of Applied Physics and Applied Mathematics, Columbia University, New York, NY, 10027, USA.
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