1
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Deng H, Liu G, Guguchia Z, Yang T, Liu J, Wang Z, Xie Y, Shao S, Ma H, Liège W, Bourdarot F, Yan XY, Qin H, Mielke C, Khasanov R, Luetkens H, Wu X, Chang G, Liu J, Christensen MH, Kreisel A, Andersen BM, Huang W, Zhao Y, Bourges P, Yao Y, Dai P, Yin JX. Evidence for time-reversal symmetry-breaking kagome superconductivity. NATURE MATERIALS 2024:10.1038/s41563-024-01995-w. [PMID: 39198714 DOI: 10.1038/s41563-024-01995-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/05/2023] [Accepted: 08/05/2024] [Indexed: 09/01/2024]
Abstract
Superconductivity and magnetism are often antagonistic in quantum matter, although their intertwining has long been considered in frustrated-lattice systems. Here we utilize scanning tunnelling microscopy and muon spin resonance to demonstrate time-reversal symmetry-breaking superconductivity in kagome metal Cs(V, Ta)3Sb5, where the Cooper pairing exhibits magnetism and is modulated by it. In the magnetic channel, we observe spontaneous internal magnetism in a fully gapped superconducting state. Under the perturbation of inverse magnetic fields, we detect a time-reversal asymmetrical interference of Bogoliubov quasi-particles at a circular vector. At this vector, the pairing gap spontaneously modulates, which is distinct from pair density waves occurring at a point vector and consistent with the theoretical proposal of an unusual interference effect under time-reversal symmetry breaking. The correlation between internal magnetism, Bogoliubov quasi-particles and pairing modulation provides a chain of experimental indications for time-reversal symmetry-breaking kagome superconductivity.
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Affiliation(s)
- Hanbin Deng
- Department of Physics, Southern University of Science and Technology, Shenzhen, China
| | - Guowei Liu
- Department of Physics, Southern University of Science and Technology, Shenzhen, China
| | - Z Guguchia
- Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institute, Villigen PSI, Aargau, Switzerland
| | - Tianyu Yang
- Department of Physics, Southern University of Science and Technology, Shenzhen, China
| | - Jinjin Liu
- Centre for Quantum Physics, Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurement (MOE), School of Physics, Beijing Institute of Technology, Beijing, China
- Beijing Key Lab of Nanophotonics and Ultrafine Optoelectronic Systems, Beijing Institute of Technology, Beijing, China
| | - Zhiwei Wang
- Centre for Quantum Physics, Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurement (MOE), School of Physics, Beijing Institute of Technology, Beijing, China.
- Beijing Key Lab of Nanophotonics and Ultrafine Optoelectronic Systems, Beijing Institute of Technology, Beijing, China.
- International Center for Quantum Materials, Beijing Institute of Technology, Zhuhai, China.
| | - Yaofeng Xie
- Department of Physics and Astronomy and Smalley-Curl Institute, Rice University, Houston, TX, USA
| | - Sen Shao
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, Singapore
| | - Haiyang Ma
- Quantum Science Center of Guangdong-Hong Kong-Macao Greater Bay Area (Guangdong), Shenzhen, China
| | - William Liège
- Laboratoire Léon Brillouin, Université Paris-Saclay, CNRS-CEA, Gif-sur-Yvette, France
| | | | - Xiao-Yu Yan
- Department of Physics, Southern University of Science and Technology, Shenzhen, China
| | - Hailang Qin
- Quantum Science Center of Guangdong-Hong Kong-Macao Greater Bay Area (Guangdong), Shenzhen, China
| | - C Mielke
- Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institute, Villigen PSI, Aargau, Switzerland
| | - R Khasanov
- Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institute, Villigen PSI, Aargau, Switzerland
| | - H Luetkens
- Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institute, Villigen PSI, Aargau, Switzerland
| | - Xianxin Wu
- CAS Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, Beijing, China
| | - Guoqing Chang
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, Singapore
| | - Jianpeng Liu
- School of Physical Science and Technology, ShanghaiTech University, Shanghai, China
| | | | - Andreas Kreisel
- Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark
| | | | - Wen Huang
- Shenzhen Institute for Quantum Science and Engineering, Southern University of Science and Technology, Shenzhen, China
| | - Yue Zhao
- Department of Physics, Southern University of Science and Technology, Shenzhen, China
| | - Philippe Bourges
- Laboratoire Léon Brillouin, Université Paris-Saclay, CNRS-CEA, Gif-sur-Yvette, France
| | - Yugui Yao
- Centre for Quantum Physics, Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurement (MOE), School of Physics, Beijing Institute of Technology, Beijing, China
- Beijing Key Lab of Nanophotonics and Ultrafine Optoelectronic Systems, Beijing Institute of Technology, Beijing, China
- International Center for Quantum Materials, Beijing Institute of Technology, Zhuhai, China
| | - Pengcheng Dai
- Department of Physics and Astronomy and Smalley-Curl Institute, Rice University, Houston, TX, USA
| | - Jia-Xin Yin
- Department of Physics, Southern University of Science and Technology, Shenzhen, China.
- Quantum Science Center of Guangdong-Hong Kong-Macao Greater Bay Area (Guangdong), Shenzhen, China.
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2
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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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3
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Mesaros A, Gu GD, Massee F. Topologically trivial gap-filling in superconducting Fe(Se,Te) by one-dimensional defects. Nat Commun 2024; 15:3774. [PMID: 38710680 DOI: 10.1038/s41467-024-48047-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2023] [Accepted: 04/15/2024] [Indexed: 05/08/2024] Open
Abstract
Structural distortions and imperfections are a crucial aspect of materials science, on the macroscopic scale providing strength, but also enhancing corrosion and reducing electrical and thermal conductivity. At the nanometre scale, multi-atom imperfections, such as atomic chains and crystalline domain walls have conversely been proposed as a route to topological superconductivity, whose most prominent characteristic is the emergence of Majorana Fermions that can be used for error-free quantum computing. Here, we shed more light on the nature of purported domain walls in Fe(Se,Te) that may host 1D dispersing Majorana modes. We show that the displacement shift of the atomic lattice at these line-defects results from sub-surface impurities that warp the topmost layer(s). Using the electric field between the tip and sample, we manage to reposition the sub-surface impurities, directly visualizing the displacement shift and the underlying defect-free lattice. These results, combined with observations of a completely different type of 1D defect where superconductivity remains fully gapped, highlight the topologically trivial nature of 1D defects in Fe(Se,Te).
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Affiliation(s)
- A Mesaros
- Université Paris-Saclay, CNRS, Laboratoire de Physique des Solides, 91405, Orsay, France
| | - G D Gu
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, NY, 11973, USA
| | - F Massee
- Université Paris-Saclay, CNRS, Laboratoire de Physique des Solides, 91405, Orsay, France.
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4
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Hu LH, Zhang RX. Dislocation Majorana bound states in iron-based superconductors. Nat Commun 2024; 15:2337. [PMID: 38491015 PMCID: PMC10943028 DOI: 10.1038/s41467-024-46618-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2022] [Accepted: 03/04/2024] [Indexed: 03/18/2024] Open
Abstract
We show that lattice dislocations of topological iron-based superconductors such as FeTe1-xSex will intrinsically trap non-Abelian Majorana quasiparticles, in the absence of any external magnetic field. Our theory is motivated by the recent experimental observations of normal-state weak topology and surface magnetism that coexist with superconductivity in FeTe1-xSex, the combination of which naturally achieves an emergent second-order topological superconductivity in a two-dimensional subsystem spanned by screw or edge dislocations. This exemplifies a new embedded higher-order topological phase in class D, where Majorana zero modes appear around the "corners" of a low-dimensional embedded subsystem, instead of those of the full crystal. A nested domain wall theory is developed to understand the origin of these defect Majorana zero modes. When the surface magnetism is absent, we further find that s± pairing symmetry itself is capable of inducing a different type of class-DIII embedded higher-order topology with defect-bound Majorana Kramers pairs. We also provide detailed discussions on the real-world material candidates for our proposals, including FeTe1-xSex, LiFeAs, β-PdBi2, and heterostructures of bismuth, etc. Our work establishes lattice defects as a new venue to achieve high-temperature topological quantum information processing.
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Affiliation(s)
- Lun-Hui Hu
- Department of Physics and Astronomy, The University of Tennessee, Knoxville, TN, USA
- Institute for Advanced Materials and Manufacturing, The University of Tennessee, Knoxville, TN, USA
- Center for Correlated Matter and School of Physics, Zhejiang University, Hangzhou, China
| | - Rui-Xing Zhang
- Department of Physics and Astronomy, The University of Tennessee, Knoxville, TN, USA.
- Institute for Advanced Materials and Manufacturing, The University of Tennessee, Knoxville, TN, USA.
- Department of Materials Science and Engineering, The University of Tennessee, Knoxville, TN, USA.
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5
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Chung PF, Venkatesan B, Su CC, Chang JT, Cheng HK, Liu CA, Yu H, Chang CS, Guan SY, Chuang TM. Design and performance of an ultrahigh vacuum spectroscopic-imaging scanning tunneling microscope with a hybrid vibration isolation system. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2024; 95:033701. [PMID: 38426899 DOI: 10.1063/5.0189100] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/27/2023] [Accepted: 02/06/2024] [Indexed: 03/02/2024]
Abstract
A spectroscopic imaging-scanning tunneling microscope (SI-STM) allows for the atomic scale visualization of the surface electronic and magnetic structure of novel quantum materials with a high energy resolution. To achieve the optimal performance, a low vibration facility is required. Here, we describe the design and performance of an ultrahigh vacuum STM system supported by a hybrid vibration isolation system that consists of a pneumatic passive and a piezoelectric active vibration isolation stage. We present the detailed vibrational noise analysis of the hybrid vibration isolation system, which shows that the vibration level can be suppressed below 10-8 m/sec/√Hz for most frequencies up to 100 Hz. Combined with a rigid STM design, vibrational noise can be successfully removed from the tunneling current. We demonstrate the performance of our STM system by taking high resolution spectroscopic maps and topographic images on several quantum materials. Our results establish a new strategy to achieve an effective vibration isolation system for high-resolution STM and other scanning probe microscopies to investigate the nanoscale quantum phenomena.
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Affiliation(s)
- Pei-Fang Chung
- Institute of Physics, Academia Sinica, Taipei 11529, Taiwan
| | - Balaji Venkatesan
- Institute of Physics, Academia Sinica, Taipei 11529, Taiwan
- Department of Physics, National Taiwan University, Taipei 10617, Taiwan
- Nano Science and Technology Program, Taiwan International Graduate Program, Academia Sinica and National Taiwan University, Taipei 11529, Taiwan
| | - Chih-Chuan Su
- Institute of Physics, Academia Sinica, Taipei 11529, Taiwan
| | - Jen-Te Chang
- Institute of Physics, Academia Sinica, Taipei 11529, Taiwan
| | - Hsu-Kai Cheng
- Institute of Physics, Academia Sinica, Taipei 11529, Taiwan
| | - Che-An Liu
- Institute of Physics, Academia Sinica, Taipei 11529, Taiwan
| | - Henry Yu
- Institute of Physics, Academia Sinica, Taipei 11529, Taiwan
| | - Chia-Seng Chang
- Institute of Physics, Academia Sinica, Taipei 11529, Taiwan
- Department of Physics, National Taiwan University, Taipei 10617, Taiwan
- Nano Science and Technology Program, Taiwan International Graduate Program, Academia Sinica and National Taiwan University, Taipei 11529, Taiwan
| | - Syu-You Guan
- Institute of Physics, Academia Sinica, Taipei 11529, Taiwan
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6
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Mandal M, Drucker NC, Siriviboon P, Nguyen T, Boonkird A, Lamichhane TN, Okabe R, Chotrattanapituk A, Li M. Topological Superconductors from a Materials Perspective. CHEMISTRY OF MATERIALS : A PUBLICATION OF THE AMERICAN CHEMICAL SOCIETY 2023; 35:6184-6200. [PMID: 37637011 PMCID: PMC10448998 DOI: 10.1021/acs.chemmater.3c00713] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/27/2023] [Revised: 07/12/2023] [Indexed: 08/29/2023]
Abstract
Topological superconductors (TSCs) have garnered significant research and industry attention in the past two decades. By hosting Majorana bound states which can be used as qubits that are robust against local perturbations, TSCs offer a promising platform toward (nonuniversal) topological quantum computation. However, there has been a scarcity of TSC candidates, and the experimental signatures that identify a TSC are often elusive. In this Perspective, after a short review of the TSC basics and theories, we provide an overview of the TSC materials candidates, including natural compounds and synthetic material systems. We further introduce various experimental techniques to probe TSCs, focusing on how a system is identified as a TSC candidate and why a conclusive answer is often challenging to draw. We conclude by calling for new experimental signatures and stronger computational support to accelerate the search for new TSC candidates.
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Affiliation(s)
- Manasi Mandal
- Quantum
Measurement Group, MIT, Cambridge, Massachusetts 02139, United States
- Department
of Nuclear Science and Engineering, MIT, Cambridge, Massachusetts 02139, United States
| | - Nathan C. Drucker
- Quantum
Measurement Group, MIT, Cambridge, Massachusetts 02139, United States
- School
of Engineering and Applied Sciences, Harvard
University, Cambridge, Massachusetts 02138, United States
| | - Phum Siriviboon
- Department
of Physics, MIT, Cambridge, Massachusetts 02139, United States
| | - Thanh Nguyen
- Quantum
Measurement Group, MIT, Cambridge, Massachusetts 02139, United States
- Department
of Nuclear Science and Engineering, MIT, Cambridge, Massachusetts 02139, United States
| | - Artittaya Boonkird
- Quantum
Measurement Group, MIT, Cambridge, Massachusetts 02139, United States
- Department
of Nuclear Science and Engineering, MIT, Cambridge, Massachusetts 02139, United States
| | - Tej Nath Lamichhane
- Quantum
Measurement Group, MIT, Cambridge, Massachusetts 02139, United States
- Department
of Nuclear Science and Engineering, MIT, Cambridge, Massachusetts 02139, United States
| | - Ryotaro Okabe
- Quantum
Measurement Group, MIT, Cambridge, Massachusetts 02139, United States
- Department
of Chemistry, MIT, Cambridge, Massachusetts 02139, United States
| | - Abhijatmedhi Chotrattanapituk
- Quantum
Measurement Group, MIT, Cambridge, Massachusetts 02139, United States
- Department
of Electrical Engineering and Computer Science, MIT, Cambridge, Massachusetts 02139, United States
| | - Mingda Li
- Quantum
Measurement Group, MIT, Cambridge, Massachusetts 02139, United States
- Department
of Nuclear Science and Engineering, MIT, Cambridge, Massachusetts 02139, United States
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7
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Ding P, Schwemmer T, Lee CH, Wu X, Thomale R. Hyperbolic Fringe Signal for Twin Impurity Quasiparticle Interference. PHYSICAL REVIEW LETTERS 2023; 130:256001. [PMID: 37418713 DOI: 10.1103/physrevlett.130.256001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/05/2022] [Revised: 10/31/2022] [Accepted: 05/17/2023] [Indexed: 07/09/2023]
Abstract
We study the quasiparticle interference (QPI) pattern emanating from a pair of adjacent impurities on the surface of a gapped superconductor (SC). We find that hyperbolic fringes (HFs) in the QPI signal can appear due to the loop contribution of the two-impurity scattering, where the locations of the two impurities are the hyperbolic focus points. For a single pocket Fermiology, a HF pattern signals chiral SC order for nonmagnetic impurities and requires magnetic impurities for a nonchiral SC. For a multipocket scenario, a sign-changing order parameter such as an s_{±} wave likewise yields a HF signature. We discuss twin impurity QPI as a new tool to complement the analysis of superconducting order from local spectroscopy.
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Affiliation(s)
- Peize Ding
- Institute for Theoretical Physics, University of Würzburg, Am Hubland, D-97074 Würzburg, Germany
- School of the Gifted Young, University of Science and Technology of China, Hefei 230026, China
- Department of Physics, Columbia University, New York, New York 10027, USA
| | - Tilman Schwemmer
- Institute for Theoretical Physics, University of Würzburg, Am Hubland, D-97074 Würzburg, Germany
| | - Ching Hua Lee
- Department of Physics, National University of Singapore, Singapore, 117542
- Joint School of National University of Singapore and Tianjin University, International Campus of Tianjin University, Binhai New City, Fuzhou 350207, China
| | - Xianxin Wu
- CAS Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Ronny Thomale
- Institute for Theoretical Physics, University of Würzburg, Am Hubland, D-97074 Würzburg, Germany
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8
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Zars E, Gravogl L, Gau MR, Carroll PJ, Meyer K, Mindiola DJ. Isostructural bridging diferrous chalcogenide cores [Fe II(μ-E)Fe II] (E = O, S, Se, Te) with decreasing antiferromagnetic coupling down the chalcogenide series. Chem Sci 2023; 14:6770-6779. [PMID: 37350823 PMCID: PMC10283490 DOI: 10.1039/d3sc01094e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2023] [Accepted: 05/24/2023] [Indexed: 06/24/2023] Open
Abstract
Iron compounds containing a bridging oxo or sulfido moiety are ubiquitous in biological systems, but substitution with the heavier chalcogenides selenium and tellurium, however, is much rarer, with only a few examples reported to date. Here we show that treatment of the ferrous starting material [(tBupyrpyrr2)Fe(OEt2)] (1-OEt2) (tBupyrpyrr2 = 3,5-tBu2-bis(pyrrolyl)pyridine) with phosphine chalcogenide reagents E = PR3 results in the neutral phosphine chalcogenide adduct series [(tBupyrpyrr2)Fe(EPR3)] (E = O, S, Se; R = Ph; E = Te; R = tBu) (1-E) without any electron transfer, whereas treatment of the anionic starting material [K]2[(tBupyrpyrr2)Fe2(μ-N2)] (2-N2) with the appropriate chalcogenide transfer source yields cleanly the isostructural ferrous bridging mono-chalcogenide ate complexes [K]2[(tBupyrpyrr2)Fe2(μ-E)] (2-E) (E = O, S, Se, and Te) having significant deviation in the Fe-E-Fe bridge from linear in the case of E = O to more acute for the heaviest chalcogenide. All bridging chalcogenide complexes were analyzed using a variety of spectroscopic techniques, including 1H NMR, UV-Vis electronic absorbtion, and 57Fe Mössbauer. The spin-state and degree of communication between the two ferrous ions were probed via SQUID magnetometry, where it was found that all iron centers were high-spin (S = 2) FeII, with magnetic exchange coupling between the FeII ions. Magnetic studies established that antiferromagnetic coupling between the ferrous ions decreases as the identity of the chalcogen is tuned from O to the heaviest congener Te.
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Affiliation(s)
- Ethan Zars
- Department of Chemistry, University of Pennsylvania 231 S 34th St Philadelphia PA 19104 USA
| | - Lisa Gravogl
- Department of Chemistry & Pharmacy, Friedrich-Alexander-Universität Erlangen - Nürnberg (FAU) Egerlandstr. 1 91058 Erlangen Bavaria Germany
| | - Michael R Gau
- Department of Chemistry, University of Pennsylvania 231 S 34th St Philadelphia PA 19104 USA
| | - Patrick J Carroll
- Department of Chemistry, University of Pennsylvania 231 S 34th St Philadelphia PA 19104 USA
| | - Karsten Meyer
- Department of Chemistry & Pharmacy, Friedrich-Alexander-Universität Erlangen - Nürnberg (FAU) Egerlandstr. 1 91058 Erlangen Bavaria Germany
| | - Daniel J Mindiola
- Department of Chemistry, University of Pennsylvania 231 S 34th St Philadelphia PA 19104 USA
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9
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Bulk evidence of anisotropic s-wave pairing with no sign change in the kagome superconductor CsV 3Sb 5. Nat Commun 2023; 14:667. [PMID: 36750576 PMCID: PMC9905511 DOI: 10.1038/s41467-023-36273-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2022] [Accepted: 01/16/2023] [Indexed: 02/09/2023] Open
Abstract
The recently discovered kagome superconductors AV3Sb5 (A = K, Rb, Cs) exhibit unusual charge-density-wave (CDW) orders with time-reversal and rotational symmetry breaking. One of the most crucial unresolved issues is identifying the symmetry of the superconductivity that develops inside the CDW phase. Theory predicts a variety of unconventional superconducting symmetries with sign-changing and chiral order parameters. Experimentally, however, superconducting phase information in AV3Sb5 is still lacking. Here we report the impurity effects in CsV3Sb5 using electron irradiation as a phase-sensitive probe of superconductivity. Our magnetic penetration depth measurements reveal that with increasing impurities, an anisotropic fully-gapped state changes to an isotropic full-gap state without passing through a nodal state. Furthermore, transport measurements under pressure show that the double superconducting dome in the pressure-temperature phase diagram survives against sufficient impurities. These results support that CsV3Sb5 is a non-chiral, anisotropic s-wave superconductor with no sign change both at ambient and under pressure.
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10
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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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11
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Hu LH, Wu X, Liu CX, Zhang RX. Competing Vortex Topologies in Iron-Based Superconductors. PHYSICAL REVIEW LETTERS 2022; 129:277001. [PMID: 36638298 DOI: 10.1103/physrevlett.129.277001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/03/2021] [Accepted: 12/07/2022] [Indexed: 06/17/2023]
Abstract
In this Letter, we establish a new theoretical paradigm for vortex Majorana physics in the recently discovered topological iron-based superconductors (TFeSCs). While TFeSCs are widely accepted as an exemplar of topological insulators (TIs) with intrinsic s-wave superconductivity, our theory implies that such a common belief could be oversimplified. Our main finding is that the normal-state bulk Dirac nodes, usually ignored in TI-based vortex Majorana theories for TFeSCs, will play a key role of determining the vortex state topology. In particular, the interplay between TI and Dirac nodal bands will lead to multiple competing topological phases for a superconducting vortex line in TFeSCs, including an unprecedented hybrid topological vortex state that carries both Majorana bound states and a gapless dispersion. Remarkably, this exotic hybrid vortex phase generally exists in the vortex phase diagram for our minimal model for TFeSCs and is directly relevant to TFeSC candidates such as LiFeAs. When the fourfold rotation symmetry is broken by vortex-line tilting or curving, the hybrid vortex gets topologically trivialized and becomes Majorana free, which could explain the puzzle of ubiquitous trivial vortices observed in LiFeAs. The origin of the Majorana signal in other TFeSC candidates such as FeTe_{x}Se_{1-x} and CaKFe_{4}As_{4} is also interpreted within our theory framework. Our theory sheds new light on theoretically understanding and experimentally engineering Majorana physics in high-temperature iron-based systems.
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Affiliation(s)
- Lun-Hui Hu
- Department of Physics and Astronomy, The University of Tennessee, Knoxville, Tennessee 37996, USA
- Institute for Advanced Materials and Manufacturing, The University of Tennessee, Knoxville, Tennessee 37920, USA
- Department of Physics, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | - Xianxin Wu
- CAS Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, Beijing 100190, China
- Max-Planck-Institut für Festkörperforschung, Heisenbergstrasse 1, D-70569 Stuttgart, Germany
| | - Chao-Xing Liu
- Department of Physics, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | - Rui-Xing Zhang
- Department of Physics and Astronomy, The University of Tennessee, Knoxville, Tennessee 37996, USA
- Institute for Advanced Materials and Manufacturing, The University of Tennessee, Knoxville, Tennessee 37920, USA
- Department of Materials Science and Engineering, The University of Tennessee, Knoxville, Tennessee 37996, USA
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12
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Abstract
SignificanceThe notion of the quantum critical point (QCP) is at the core of modern condensed matter physics. Near a QCP of the symmetry-breaking order, associated quantum-mechanical fluctuations are intensified, which can lead to unconventional superconductivity. Indeed, dome-shaped superconducting phases are often observed near the magnetic QCPs, which supports the spin fluctuation-driven superconductivity. However, the fundamental question remains as to whether a nonmagnetic QCP of electronic nematic order characterized by spontaneous rotational symmetry breaking can promote superconductivity in real materials. Here, we provide an experimental demonstration that a pure nematic QCP exists near the center of a superconducting dome in nonmagnetic FeSe[Formula: see text] Tex. This result evidences that nematic fluctuations enhanced around the nematic QCP can boost superconductivity.
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13
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Zhang Y, Zhao WM, Zhang C, Wang P, Wang T, Li SC, Xing Z, Xing D. Anomalous Superconducting Proximity Effect in Bi 2 Se 3 /FeSe 0.5 Te 0.5 Thin-Film Heterojunctions. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2022; 34:e2107799. [PMID: 34818689 DOI: 10.1002/adma.202107799] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/29/2021] [Revised: 11/19/2021] [Indexed: 06/13/2023]
Abstract
The superconducting proximity effect (SPE) induces a superconductivity transition in otherwise non-superconducting thin films in proximity with a superconductor. The SPE usually occurs in real space and decays exponentially with film thickness. Herein, an abnormal SPE in a topological insulator (TI)/superconductor heterostructure is unveiled, which is attributed to the topologically protected surface state. Surprisingly, such abnormal SPE occurs in momentum space regardless of the TI film thickness, as long as the topological surface states are robust and form a continuous conduction loop. Combining transport measurements and scanning tunneling microscopy/spectroscopy techniques, the SPE in Bi2 Se3 /FeSe0.5 Te0.5 heterostructures is explored, where Bi2 Se3 is an ideal 3D topological insulator and FeSe0.5 Te0.5 a typical iron-based superconductor. As the thickness of the Bi2 Se3 thin film exceeds 400 nm, there still exists SPE-induced superconductivity on the surface of Bi2 Se3 thin film with a transition temperature Tc not less than 10 K. Such an extraordinary behavior is induced by the unique properties of topologically protected surface states of Bi2 Se3 . This research deepens the understanding of the important role of topologically protected surface states in the SPE.
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Affiliation(s)
- Yalin Zhang
- National Laboratory of Solid State Microstructures, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, 210093, China
- College of Engineering and Applied Sciences, Nanjing University, Nanjing, 210093, China
| | - Wei-Min Zhao
- National Laboratory of Solid State Microstructures, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, 210093, China
- School of Physics, Nanjing University, Nanjing, 210093, China
| | - Chunchen Zhang
- National Laboratory of Solid State Microstructures, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, 210093, China
- College of Engineering and Applied Sciences, Nanjing University, Nanjing, 210093, China
| | - Peng Wang
- National Laboratory of Solid State Microstructures, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, 210093, China
- College of Engineering and Applied Sciences, Nanjing University, Nanjing, 210093, China
| | - Tong Wang
- Department of Mathematics, Nanjing University of Aeronautics and Astronautics, Nanjing, 210016, China
| | - Shao-Chun Li
- National Laboratory of Solid State Microstructures, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, 210093, China
- School of Physics, Nanjing University, Nanjing, 210093, China
| | - Zhongwen Xing
- National Laboratory of Solid State Microstructures, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, 210093, China
- School of Electronic Science and Engineering, Nanjing University, Nanjing, 210093, China
| | - Dingyu Xing
- National Laboratory of Solid State Microstructures, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, 210093, China
- School of Physics, Nanjing University, Nanjing, 210093, China
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14
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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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15
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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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16
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Multiplicity, Parity and Angular Momentum of a Cooper Pair in Unconventional Superconductors of D4h Symmetry: Sr2RuO4 and Fe-Pnictide Materials. Symmetry (Basel) 2021. [DOI: 10.3390/sym13081435] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Sr2RuO4 and Fe-pnictide superconductors belong to the same point group symmetry D4h. Many experimental data confirm odd pairs in Sr2RuO4 and even pairs in Fe-pnictides, but opposite conclusions also exist. Recent NMR results of Pustogow et al., which revealed even Cooper pairs in Sr2RuO4, require reconsideration of symmetry treatment of its SOP (superconducting order parameter). In the present work making use of the Mackey–Bradley theorem on symmetrized squares, a group theoretical investigation of possible pairing states in D4h symmetry is performed. It is obtained for I4/mmm , i.e., space group of Sr2RuO4, that triplet pairs with even spatial parts are possible in kz direction and in points M and Y. For the two latter cases pairing of equivalent electrons with nonzero total momentum is proposed. In P4/nmm space group of Fe- pnictides in point M, even and odd pairs are possible for singlet and triplet cases. It it shown that even and odd chiral states with angular momentum projection m=±1 have nodes in vertical planes, but Eg is nodal , whereas Eu is nodeless in the basal plane. It is also shown that the widely accepted assertion that the parity of angular momentum value is directly connected with the spatial parity of a pair is not valid in a space-group approach to the wavefunction of a Cooper pair.
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17
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Jiang D, Pan Y, Wang S, Lin Y, Holland CM, Kirtley JR, Chen X, Zhao J, Chen L, Yin S, Wang Y. Observation of robust edge superconductivity in Fe(Se,Te) under strong magnetic perturbation. Sci Bull (Beijing) 2021; 66:425-432. [PMID: 36654179 DOI: 10.1016/j.scib.2020.10.006] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2020] [Revised: 09/04/2020] [Accepted: 09/29/2020] [Indexed: 01/20/2023]
Abstract
The iron-chalcogenide high temperature superconductor Fe(Se,Te) (FST) has been reported to exhibit complex magnetic ordering and nontrivial band topology which may lead to novel superconducting phenomena. However, the recent studies have so far been largely concentrated on its band and spin structures while its mesoscopic electronic and magnetic response, crucial for future device applications, has not been explored experimentally. Here, we used scanning superconducting quantum interference device microscopy for its sensitivity to both local diamagnetic susceptibility and current distribution in order to image the superfluid density and supercurrent in FST. We found that in FST with 10% interstitial Fe, whose magnetic structure was heavily disrupted, bulk superconductivity was significantly suppressed whereas edge still preserved strong superconducting diamagnetism. The edge dominantly carried supercurrent despite of a very long magnetic penetration depth. The temperature dependences of the superfluid density and supercurrent distribution were distinctively different between the edge and the bulk. Our Heisenberg modeling showed that magnetic dopants stabilize anti-ferromagnetic spin correlation along the edge, which may contribute towards its robust superconductivity. Our observations hold implication for FST as potential platforms for topological quantum computation and superconducting spintronics.
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Affiliation(s)
- Da Jiang
- Shanghai Institute of Microsystem and Information Technology, Shanghai 200050, China.
| | - Yinping Pan
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China
| | - Shiyuan Wang
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China
| | - Yishi Lin
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China
| | - Connor M Holland
- Department of Physics, Stanford University, Stanford, CA 94305, USA
| | - John R Kirtley
- Department of Physics, Stanford University, Stanford, CA 94305, USA
| | - Xianhui Chen
- Department of Physics, University of Science and Technology of China, Hefei 230026, China
| | - Jun Zhao
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China
| | - Lei Chen
- Shanghai Institute of Microsystem and Information Technology, Shanghai 200050, China
| | - Shaoyu Yin
- Institute for Theoretical Physics and Cosmology, Zhejiang University of Technology, Hangzhou 310023, China; State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China.
| | - Yihua Wang
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China; Shanghai Research Center for Quantum Sciences, Shanghai 201315, China.
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18
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Abstract
FeSe is classed as a Hund’s metal, with a multiplicity of d bands near the Fermi level. Correlations in Hund’s metals mostly originate from the exchange parameter J, which can drive a strong orbital selectivity in the correlations. The Fe-chalcogens are the most strongly correlated of the Fe-based superconductors, with dxy the most correlated orbital. Yet little is understood whether and how such correlations directly affect the superconducting instability in Hund’s systems. By applying a recently developed ab initio theory, we show explicitly the connections between correlations in dxy and the superconducting critical temperature Tc. Starting from the ab initio results as a reference, we consider various kinds of excursions in parameter space around the reference to determine what controls Tc. We show small excursions in J can cause colossal changes in Tc. Additionally we consider changes in hopping by varying the Fe-Se bond length in bulk, in the free standing monolayer M-FeSe, and M-FeSe on a SrTiO3 substrate (M-FeSe/STO). The twin conditions of proximity of the dxy state to the Fermi energy, and the strength of J emerge as the primary criteria for incoherent spectral response and enhanced single- and two-particle scattering that in turn controls Tc. Using c-RPA, we show further that FeSe in monolayer form (M-FeSe) provides a natural mechanism to enhance J. We explain why M-FeSe/STO has a high Tc, whereas M-FeSe in isolation should not. Our study opens a paradigm for a unified understanding what controls Tc in bulk, layers, and interfaces of Hund’s metals by hole pocket and electron screening cloud engineering.
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19
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High-pressure phase diagrams of FeSe 1-xTe x: correlation between suppressed nematicity and enhanced superconductivity. Nat Commun 2021; 12:381. [PMID: 33452257 PMCID: PMC7810696 DOI: 10.1038/s41467-020-20621-2] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2020] [Accepted: 12/13/2020] [Indexed: 11/23/2022] Open
Abstract
The interplay among magnetism, electronic nematicity, and superconductivity is the key issue in strongly correlated materials including iron-based, cuprate, and heavy-fermion superconductors. Magnetic fluctuations have been widely discussed as a pairing mechanism of unconventional superconductivity, but recent theory predicts that quantum fluctuations of nematic order may also promote high-temperature superconductivity. This has been studied in FeSe1−xSx superconductors exhibiting nonmagnetic nematic and pressure-induced antiferromagnetic orders, but its abrupt suppression of superconductivity at the nematic end point leaves the nematic-fluctuation driven superconductivity unconfirmed. Here we report on systematic studies of high-pressure phase diagrams up to 8 GPa in high-quality single crystals of FeSe1−xTex. When Te composition x(Te) becomes larger than 0.1, the high-pressure magnetic order disappears, whereas the pressure-induced superconducting dome near the nematic end point is continuously found up to x(Te) ≈ 0.5. In contrast to FeSe1−xSx, enhanced superconductivity in FeSe1−xTex does not correlate with magnetism but with the suppression of nematicity, highlighting the paramount role of nonmagnetic nematic fluctuations for high-temperature superconductivity in this system. Despite studies in FeSe1−xSx, it is yet unconfirmed whether nematic fluctuation can induce superconductivity. Here, the authors study single crystals of FeSe1−xTex showing enhanced superconductivity upon suppression of nematicity.
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20
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Vaswani C, Kang JH, Mootz M, Luo L, Yang X, Sundahl C, Cheng D, Huang C, Kim RHJ, Liu Z, Collantes YG, Hellstrom EE, Perakis IE, Eom CB, Wang J. Light quantum control of persisting Higgs modes in iron-based superconductors. Nat Commun 2021; 12:258. [PMID: 33431843 PMCID: PMC7801641 DOI: 10.1038/s41467-020-20350-6] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2020] [Accepted: 11/30/2020] [Indexed: 11/28/2022] Open
Abstract
The Higgs mechanism, i.e., spontaneous symmetry breaking of the quantum vacuum, is a cross-disciplinary principle, universal for understanding dark energy, antimatter and quantum materials, from superconductivity to magnetism. Unlike one-band superconductors (SCs), a conceptually distinct Higgs amplitude mode can arise in multi-band, unconventional superconductors via strong interband Coulomb interaction, but is yet to be accessed. Here we discover such hybrid Higgs mode and demonstrate its quantum control by light in iron-based high-temperature SCs. Using terahertz (THz) two-pulse coherent spectroscopy, we observe a tunable amplitude mode coherent oscillation of the complex order parameter from coupled lower and upper bands. The nonlinear dependence of the hybrid Higgs mode on the THz driving fields is distinct from any known SC results: we observe a large reversible modulation of resonance strength, yet with a persisting mode frequency. Together with quantum kinetic modeling of a hybrid Higgs mechanism, distinct from charge-density fluctuations and without invoking phonons or disorder, our result provides compelling evidence for a light-controlled coupling between the electron and hole amplitude modes assisted by strong interband quantum entanglement. Such light-control of Higgs hybridization can be extended to probe many-body entanglement and hidden symmetries in other complex systems. A collective excitation called Higgs mode may arise in multi-band superconductors via strong interband interaction, but it is yet to be accessed. Here, the authors observe a tunable coherent amplitude oscillation of the order parameter in Ba(Fe1−xCox)2As2, suggesting appearance and control of the Higgs mode by light tuning interband interaction.
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Affiliation(s)
- C Vaswani
- Department of Physics and Astronomy, Iowa State University, and Ames Laboratory, Ames, IA, 50011, USA
| | - J H Kang
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - M Mootz
- Department of Physics, University of Alabama at Birmingham, Birmingham, AL, 35294-1170, USA
| | - L Luo
- Department of Physics and Astronomy, Iowa State University, and Ames Laboratory, Ames, IA, 50011, USA
| | - X Yang
- Department of Physics and Astronomy, Iowa State University, and Ames Laboratory, Ames, IA, 50011, USA
| | - C Sundahl
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - D Cheng
- Department of Physics and Astronomy, Iowa State University, and Ames Laboratory, Ames, IA, 50011, USA
| | - C Huang
- Department of Physics and Astronomy, Iowa State University, and Ames Laboratory, Ames, IA, 50011, USA
| | - R H J Kim
- Department of Physics and Astronomy, Iowa State University, and Ames Laboratory, Ames, IA, 50011, USA
| | - Z Liu
- Department of Physics and Astronomy, Iowa State University, and Ames Laboratory, Ames, IA, 50011, USA
| | - Y G Collantes
- Applied Superconductivity Center, National High Magnetic Field Laboratory, Florida State University, Tallahassee, FL, 32310, USA
| | - E E Hellstrom
- Applied Superconductivity Center, National High Magnetic Field Laboratory, Florida State University, Tallahassee, FL, 32310, USA
| | - I E Perakis
- Department of Physics, University of Alabama at Birmingham, Birmingham, AL, 35294-1170, USA
| | - C B Eom
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - J Wang
- Department of Physics and Astronomy, Iowa State University, and Ames Laboratory, Ames, IA, 50011, USA.
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21
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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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22
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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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23
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Lazarević N, Hackl R. Fluctuations and pairing in Fe-based superconductors: light scattering experiments. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2020; 32:413001. [PMID: 32272462 DOI: 10.1088/1361-648x/ab8849] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/14/2019] [Accepted: 04/09/2020] [Indexed: 06/11/2023]
Abstract
Inelastic scattering of visible light (Raman effect) offers a window into properties of correlated metals such as spin, electron and lattice dynamics as well as their mutual interactions. In this review we focus on electronic and spin excitations in Fe-based pnictides and chalcogenides, in particular but not exclusively superconductors. After a general introduction to the basic theory including the selection rules for the various scattering processes we provide an overview over the major experimental results. In the superconducting state below the transition temperatureTcthe pair-breaking effect can be observed, and the gap energies may be derived and associated with the gaps on the electron and hole bands. In spite of the similarities of the overall band structures the results are strongly dependent on the family and may even change qualitatively within one family. In some of the compounds strong collective modes appear belowTc. In Ba1-xKxFe2As2, which has the most isotropic gap of all Fe-based superconductors, there are indications that these modes are exciton-like states appearing in the presence of a hierarchy of pairing tendencies. The strong in-gap modes observed in Co-doped NaFeAs are interpreted in terms of quadrupolar orbital excitations which become undamped in the superconducting state. The doping dependence of the scattering intensity in Ba(Fe1-xCox)2As2is associated with a nematic resonance above a quantum critical point and interpreted in terms of a critical enhancement at the maximalTc. In the normal state the response from particle-hole excitations reflects the resistivity. In addition, there are strongly temperature-dependent contributions from presumably critical fluctuations in the energy range ofkBTwhich can be compared to the elastic properties. Currently it is not settled whether the fluctuations observed by light scattering are related to spin or charge. Another controversy relates to putative two-magnon excitations, typically in the energy range below 0.5 eV. Whereas this response presumably originates from charge excitations in most of the Fe-based compounds theory and experiment suggest that the excitations in the 60 meV range in FeSe stem from localized spins in a nearly frustrated system.
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Affiliation(s)
- N Lazarević
- Center for Solid State Physics and New Materials, Institute of Physics Belgrade, University of Belgrade, Pregrevica 118, 11080 Belgrade, Serbia
| | - R Hackl
- Walther Meissner Institut, Bayerische Akademie der Wissenschaften, 85748 Garching, Germany
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24
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Tranquada JM, Xu G, Zaliznyak IA. Magnetism and superconductivity in Fe 1+y Te 1-xSe x. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2020; 32:374003. [PMID: 31412327 DOI: 10.1088/1361-648x/ab3b3b] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/11/2019] [Accepted: 08/14/2019] [Indexed: 06/10/2023]
Abstract
Neutron scattering has played a significant role in characterizing magnetic and structural correlations in Fe1+y Te1-xSexand their connections with superconductivity. Here we review several key aspects of the physics of iron chalcogenide superconductors where neutron studies played a key role. These topics include the phase diagram of Fe1+y Te1-xSex, where the doping-dependence of structural transitions can be understood from a mapping to the anisotropic random field Ising model. We then discuss orbital-selective Mott physics in the Fe chalcogenide series, where temperature-dependent magnetism in the parent material provided one of the earliest cases for orbital-selective correlation effects in a Hund's metal. Finally, we elaborate on the character of local magnetic correlations revealed by neutron scattering, its dependence on temperature and composition, and the connections to nematicity and superconductivity.
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Affiliation(s)
- J M Tranquada
- Brookhaven National Laboratory, Condensed Matter & Materials Science Division, Upton, NY 11973-5000, United States of America
| | - Guangyong Xu
- NIST Center for Neutron Research, National Institute of Standards and Technology, 100 Bureau Drive, Gaithersburg, MD 20899, United States of America
| | - I A Zaliznyak
- Brookhaven National Laboratory, Condensed Matter & Materials Science Division, Upton, NY 11973-5000, United States of America
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25
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Chen X, Chen M, Duan W, Yang H, Wen HH. Robust Zero Energy Modes on Superconducting Bismuth Islands Deposited on Fe(Te,Se). NANO LETTERS 2020; 20:2965-2972. [PMID: 31995387 DOI: 10.1021/acs.nanolett.9b04639] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Topological superconductivity is one of the frontier research directions in condensed matter physics. One of the unique elementary excitations in topological superconducting state is the Majorana Fermion (mode) which is its own antiparticle and obeys the non-Abelian statistics and is thus useful for constructing the fault-tolerant quantum computation. The evidence for Majorana Fermions (mode) in condensed matter is now quickly accumulated. We deposit Bi islands on the iron-based superconductors Fe(Te,Se) and find the easily achievable zero energy modes on the tunneling spectra on some Bi islands. The zero energy mode is robust and appears everywhere on the island. Temperature and magnetic field dependence of the zero energy mode are also investigated. We attribute these zero energy modes to the Majorana modes due to the proximity effect-induced topological superconductivity on the Bi islands with strong spin-orbit coupling effect.
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Affiliation(s)
- Xiaoyu Chen
- 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 210093, China
| | - Mingyang Chen
- 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 210093, China
| | - Wen Duan
- 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 210093, 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 210093, 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 210093, China
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26
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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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27
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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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28
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Wang Z, Rodriguez JO, Jiao L, Howard S, Graham M, Gu GD, Hughes TL, Morr DK, Madhavan V. Evidence for dispersing 1D Majorana channels in an iron-based superconductor. Science 2020; 367:104-108. [DOI: 10.1126/science.aaw8419] [Citation(s) in RCA: 80] [Impact Index Per Article: 20.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2019] [Revised: 07/20/2019] [Accepted: 11/14/2019] [Indexed: 02/02/2023]
Abstract
The possible realization of Majorana fermions as quasiparticle excitations in condensed-matter physics has created much excitement. Most studies have focused on Majorana bound states; however, propagating Majorana states with linear dispersion have also been predicted. Here, we report scanning tunneling spectroscopic measurements of crystalline domain walls (DWs) in FeSe0.45Te0.55. We located DWs across which the lattice structure shifts by half a unit cell. These DWs have a finite, flat density of states inside the superconducting gap, which is a hallmark of linearly dispersing modes in one dimension. This signature is absent in DWs in the related superconductor, FeSe, which is not in the topological phase. Our combined data are consistent with the observation of dispersing Majorana states at a π-phase shift DW in a proximitized topological material.
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29
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Zhang RX, Cole WS, Wu X, Das Sarma S. Higher-Order Topology and Nodal Topological Superconductivity in Fe(Se,Te) Heterostructures. PHYSICAL REVIEW LETTERS 2019; 123:167001. [PMID: 31702343 DOI: 10.1103/physrevlett.123.167001] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/12/2019] [Revised: 08/28/2019] [Indexed: 06/10/2023]
Abstract
We show, theoretically, that a heterostructure of monolayer FeTe_{1-x}Se_{x}-a superconducting quantum spin Hall material-with a monolayer of FeTe-a bicollinear antiferromagnet-realizes a higher order topological superconductor phase characterized by emergent Majorana zero modes pinned to the sample corners. We provide a minimal effective model for this system, analyze the origin of higher order topology, and fully characterize the topological phase diagram. Despite the conventional s-wave pairing, we find a rather surprising emergence of a novel topological nodal superconductor in the phase diagram. Featured by edge-dependent Majorana flat bands, the topological nodal phase is protected by an antiferromagnetic chiral symmetry. We also discuss the experimental feasibility, the estimation of realistic model parameters, and the robustness of the Majorana corner modes against magnetic and potential disorder. Our work provides a new experimentally feasible high-temperature platform for both higher order topology and non-Abelian Majorana physics.
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Affiliation(s)
- Rui-Xing Zhang
- Condensed Matter Theory Center and Joint Quantum Institute, Department of Physics, University of Maryland, College Park, Maryland 20742-4111, USA
| | - William S Cole
- Condensed Matter Theory Center and Joint Quantum Institute, Department of Physics, University of Maryland, College Park, Maryland 20742-4111, USA
| | - Xianxin Wu
- Institut für Theoretische Physik und Astrophysik, Universität Würzburg, Am Hubland Campus Süd, Würzburg 97074, Germany
| | - S Das Sarma
- Condensed Matter Theory Center and Joint Quantum Institute, Department of Physics, University of Maryland, College Park, Maryland 20742-4111, USA
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30
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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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31
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Gray MJ, Freudenstein J, Zhao SYF, O'Connor R, Jenkins S, Kumar N, Hoek M, Kopec A, Huh S, Taniguchi T, Watanabe K, Zhong R, Kim C, Gu GD, Burch KS. Evidence for Helical Hinge Zero Modes in an Fe-Based Superconductor. NANO LETTERS 2019; 19:4890-4896. [PMID: 31268723 DOI: 10.1021/acs.nanolett.9b00844] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Combining topology and superconductivity provides a powerful tool for investigating fundamental physics as well as a route to fault-tolerant quantum computing. There is mounting evidence that the Fe-based superconductor FeTe0.55Se0.45 (FTS) may also be topologically nontrivial. Should the superconducting order be s±, then FTS could be a higher order topological superconductor with helical hinge zero modes (HHZMs). To test the presence of these modes, we have fabricated normal-metal/superconductor junctions on different surfaces via 2D atomic crystal heterostructures. As expected, junctions in contact with the hinge reveal a sharp zero bias anomaly that is absent when tunneling purely into the c-axis. Additionally, the shape and suppression with temperature are consistent with highly coherent modes along the hinge and are incongruous with other origins of zero bias anomalies. Additional measurements with soft-point contacts in bulk samples with various Fe interstitial contents demonstrate the intrinsic nature of the observed mode. Thus, we provide evidence that FTS is indeed a higher order topological superconductor.
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Affiliation(s)
- Mason J Gray
- Department of Physics , Boston College , Chestnut Hill , Massachusetts 02467 , United States
| | - Josef Freudenstein
- Department of Physics , Boston College , Chestnut Hill , Massachusetts 02467 , United States
| | - Shu Yang F Zhao
- Department of Physics , Harvard University , Cambridge , Massachusetts 02138 , United States
| | - Ryan O'Connor
- Department of Physics , Boston College , Chestnut Hill , Massachusetts 02467 , United States
| | - Samuel Jenkins
- Department of Physics , Boston College , Chestnut Hill , Massachusetts 02467 , United States
| | - Narendra Kumar
- Department of Physics , Boston College , Chestnut Hill , Massachusetts 02467 , United States
| | - Marcel Hoek
- Department of Physics , Boston College , Chestnut Hill , Massachusetts 02467 , United States
| | - Abigail Kopec
- Department of Physics , Boston College , Chestnut Hill , Massachusetts 02467 , United States
| | - Soonsang Huh
- Department of Physics and Astronomy , Seoul National University (SNU) , Seoul 08826 , Republic of Korea
| | - Takashi Taniguchi
- National Institute for Materials Science , 1-1 Namiki , Tsukuba 306-0044 , Japan
| | - Kenji Watanabe
- National Institute for Materials Science , 1-1 Namiki , Tsukuba 306-0044 , Japan
| | - Ruidan Zhong
- Condensed Matter Physics and Materials Science Department , Brookhaven National Laboratory , Upton , New York 11973 , United States
| | - Changyoung Kim
- Department of Physics and Astronomy , Seoul National University (SNU) , Seoul 08826 , Republic of Korea
| | - G D Gu
- Condensed Matter Physics and Materials Science Department , Brookhaven National Laboratory , Upton , New York 11973 , United States
| | - K S Burch
- Department of Physics , Boston College , Chestnut Hill , Massachusetts 02467 , United States
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32
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Machida T, Sun Y, Pyon S, Takeda S, Kohsaka Y, Hanaguri T, Sasagawa T, Tamegai T. Zero-energy vortex bound state in the superconducting topological surface state of Fe(Se,Te). NATURE MATERIALS 2019; 18:811-815. [PMID: 31209388 DOI: 10.1038/s41563-019-0397-1] [Citation(s) in RCA: 59] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/20/2018] [Accepted: 05/08/2019] [Indexed: 06/09/2023]
Abstract
Majorana quasiparticles in condensed matter are important for topological quantum computing1-3, but remain elusive. Vortex cores of topological superconductors may accommodate Majorana quasiparticles that appear as the Majorana bound state (MBS) at zero energy4,5. The iron-based superconductor Fe(Se,Te) possesses a superconducting topological surface state6-9 that was investigated by scanning tunnelling microscopy (STM) studies, which suggest such a zero-energy vortex bound state (ZVBS)10,11. Here we present ultrahigh energy-resolution spectroscopic imaging (SI)-STM to clarify the nature of the vortex bound states in Fe(Se,Te). We found the ZVBS at 0 ± 20 μeV, which constrained its MBS origin, and showed that some vortices host the ZVBS but others do not. We show that the fraction of vortices hosting the ZVBS decreases with increasing magnetic field and that local quenched disorders are not related to the ZVBS. Our observations elucidate the necessary conditions to realize the ZVBS, which paves the way towards controllable Majorana quasiparticles.
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Affiliation(s)
- T Machida
- RIKEN Center for Emergent Matter Science, Wako, Japan.
| | - Y Sun
- Department of Physics and Mathematics, Aoyama Gakuin University, Chuou-ku, Sagamihara, Japan
| | - S Pyon
- Department of Applied Physics, The University of Tokyo, Bunkyo-ku, Japan
| | - S Takeda
- Laboratory for Materials and Structures, Tokyo Institute of Technology, Midori-ku, Yokohama, Japan
| | - Y Kohsaka
- RIKEN Center for Emergent Matter Science, Wako, Japan
| | - T Hanaguri
- RIKEN Center for Emergent Matter Science, Wako, Japan.
| | - T Sasagawa
- Laboratory for Materials and Structures, Tokyo Institute of Technology, Midori-ku, Yokohama, Japan
| | - T Tamegai
- Department of Applied Physics, The University of Tokyo, Bunkyo-ku, Japan
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33
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A strongly inhomogeneous superfluid in an iron-based superconductor. Nature 2019; 571:541-545. [DOI: 10.1038/s41586-019-1408-8] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2018] [Accepted: 05/02/2019] [Indexed: 11/08/2022]
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34
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Tang F, Wang P, Wang P, Gan Y, Gu GD, Zhang W, He M, Zhang L. Quasi-2D superconductivity in FeTe 0.55Se 0.45 ultrathin film. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2019; 31:265702. [PMID: 30925488 DOI: 10.1088/1361-648x/ab14c3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Iron-chalcogenide FeTe0.55Se0.45 was found to be a promising topological superconducting candidate recently, which may host Majorana bound state in the vortex core and thus attracts intensive research interests in this material. In this report, mechanically exfoliated FeTe0.55Se0.45 superconducting thin films close to the two-dimensional (2D) limit, i.e. sample thickness is on the order of coherence length, were studied systematically by means of electrical transport and point-contact Andreev-reflection spectroscopy (PCARS) measurements. The quasi-2D nature of FeTe0.55Se0.45 thin films is evidenced by the observation of Berezinskii-Kosterlitz-Thouless (BKT) transition and anisotropic upper critical fields in the vicinity of superconducting transition. Compared to bulk samples, we found that the superconducting transition temperature is only slightly suppressed even for films down to 5 nm. The superconducting gap symmetry remains unchanged and the gap size is weakly affected by tailoring thickness. Our findings suggest that the superconductivity of FeTe0.55Se0.45 thin films is rather robust against reduced dimensions. It provides a novel platform for device applications for quantum computations in combination with possible realization of Majorana modes in this material.
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Affiliation(s)
- Fangdong Tang
- Department of Physics and Beijing Key Laboratory of Optoelectronic Functional Materials and Micro-nano Devices, Renmin University of China, Beijing 100872, People's Republic of China. Department of Physics, Southern University of Science and Technology, Shenzhen Institute for Quantum Science and Engineering, Shenzhen, 518055, People's Republic of China
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35
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Meng W, Wang J, Hou Y, Sui M, Zhou H, Wang J, Wu G, Zhang J, Chen F, Luo X, Sun Y, Li J, Lu Q. Atomically resolved probe-type scanning tunnelling microscope for use in harsh vibrational cryogen-free superconducting magnet. Ultramicroscopy 2019; 205:20-26. [PMID: 31234099 DOI: 10.1016/j.ultramic.2019.06.006] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2018] [Revised: 05/15/2019] [Accepted: 06/10/2019] [Indexed: 11/28/2022]
Abstract
We present a probe-type scanning tunnelling microscope (STM) with atomic resolution that is designed to be directly inserted and work in a harsh vibrational cryogen-free superconducting magnet system. When a commercial variable temperature insert (VTI) is installed in the magnet and the STM is housed in the VTI, a lowest temperature of 1.6 K can be achieved, at which the STM still operates well. We tested the STM in an 8 T superconducting magnet cooled with a pulse-tube cryocooler and obtained atomically resolved graphite and NbSe2 images as well as the scanning tunnelling spectrum (i.e., dI/dV spectrum) data of the latter near its critical temperature, which show the formation process of the superconducting gap as a function of temperature. The drifting rates of the STM at 1.6 K in the X-Y plane and Z direction are 1.15 and 1.71 pm/min, respectively. Noise analysis for the tunnelling current shows that the amplitudes of the dominant peaks (6.84 and 10.25 Hz) are as low as 1.5 pA.Hz-1/2 when we set the current to 0.5 nA and open the feedback loop. This is important as a cryogen-free magnet system has long been considered too harsh for any atomic resolution measurement.
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Affiliation(s)
- Wenjie Meng
- Anhui Province Key Laboratory of Condensed Matter Physics at Extreme Conditions, High Magnetic Field Laboratory of the Chinese Academy of Sciences, Hefei, Anhui 230031, People's Republic of China; CASmF Sci.&Tech. Ltd. , Hefei, Anhui 230088, People's Republic of China
| | - Jihao Wang
- Anhui Province Key Laboratory of Condensed Matter Physics at Extreme Conditions, High Magnetic Field Laboratory of the Chinese Academy of Sciences, Hefei, Anhui 230031, People's Republic of China; CASmF Sci.&Tech. Ltd. , Hefei, Anhui 230088, People's Republic of China
| | - Yubin Hou
- Anhui Province Key Laboratory of Condensed Matter Physics at Extreme Conditions, High Magnetic Field Laboratory of the Chinese Academy of Sciences, Hefei, Anhui 230031, People's Republic of China; CASmF Sci.&Tech. Ltd. , Hefei, Anhui 230088, People's Republic of China.
| | - Mengqiao Sui
- NanoScience devision, Oxford Instruments Technology (Shanghai) Co., Ltd., Shanghai, 200233, People's Republic of China
| | - Haibiao Zhou
- Anhui Province Key Laboratory of Condensed Matter Physics at Extreme Conditions, High Magnetic Field Laboratory of the Chinese Academy of Sciences, Hefei, Anhui 230031, People's Republic of China; Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui 230026, People's Republic of China
| | - Junting Wang
- Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui 230026, People's Republic of China
| | - Gang Wu
- NanoScience devision, Oxford Instruments Technology (Shanghai) Co., Ltd., Shanghai, 200233, People's Republic of China
| | - Jing Zhang
- Anhui Province Key Laboratory of Condensed Matter Physics at Extreme Conditions, High Magnetic Field Laboratory of the Chinese Academy of Sciences, Hefei, Anhui 230031, People's Republic of China; CASmF Sci.&Tech. Ltd. , Hefei, Anhui 230088, People's Republic of China
| | - Fangchu Chen
- Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei, 230031, People's Republic of China
| | - Xuan Luo
- Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei, 230031, People's Republic of China
| | - Yupin Sun
- Anhui Province Key Laboratory of Condensed Matter Physics at Extreme Conditions, High Magnetic Field Laboratory of the Chinese Academy of Sciences, Hefei, Anhui 230031, People's Republic of China; Collaborative Innovation Center for Artificial Microstructure and Quantum Control, Nanjing University, Nanjing 210093, People's Republic of China; Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei, 230031, People's Republic of China
| | - Junyun Li
- NanoScience devision, Oxford Instruments Technology (Shanghai) Co., Ltd., Shanghai, 200233, People's Republic of China
| | - Qingyou Lu
- Anhui Province Key Laboratory of Condensed Matter Physics at Extreme Conditions, High Magnetic Field Laboratory of the Chinese Academy of Sciences, Hefei, Anhui 230031, People's Republic of China; CASmF Sci.&Tech. Ltd. , Hefei, Anhui 230088, People's Republic of China; Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui 230026, People's Republic of China; Collaborative Innovation Center for Artificial Microstructure and Quantum Control, Nanjing University, Nanjing 210093, People's Republic of China; Anhui Laboratory of Advanced Photon Science and Technology, University of Science and Technology of China, Hefei, Anhui 230026, People's Republic of China.
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36
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Zhang RX, Cole WS, Das Sarma S. Helical Hinge Majorana Modes in Iron-Based Superconductors. PHYSICAL REVIEW LETTERS 2019; 122:187001. [PMID: 31144910 DOI: 10.1103/physrevlett.122.187001] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/04/2019] [Indexed: 06/09/2023]
Abstract
Motivated by recent experiments on FeTe_{1-x}Se_{x}, we construct an explicit minimal model of an iron-based superconductor with band inversion at the Z point and nontopological bulk s_{±} pairing. While there has been considerable interest in Majorana zero modes localized at vortices in such systems, we find that our model-without any vortices-intrinsically supports 1D helical Majorana modes localized at the hinges between (001) and (100) or (010) surfaces, suggesting that this is a viable platform for observing "higher-order" topological superconductivity. We provide a general theory for these hinge modes and discuss their stability and experimental manifestation. Our work indicates the possible experimental observability of hinge Majorana modes in iron-based topological superconductors.
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Affiliation(s)
- Rui-Xing Zhang
- Condensed Matter Theory Center and Joint Quantum Institute, Department of Physics, University of Maryland, College Park, Maryland 20742-4111, USA
| | - William S Cole
- Condensed Matter Theory Center and Joint Quantum Institute, Department of Physics, University of Maryland, College Park, Maryland 20742-4111, USA
| | - S Das Sarma
- Condensed Matter Theory Center and Joint Quantum Institute, Department of Physics, University of Maryland, College Park, Maryland 20742-4111, USA
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37
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Chen L, Liu H, Jiang C, Shi C, Wang D, Cui G, Li X, Zhuang Q. Topological edge states in high-temperature superconductiving FeSe/SrTiO 3 films with Te substitution. Sci Rep 2019; 9:4154. [PMID: 30858432 PMCID: PMC6411874 DOI: 10.1038/s41598-019-40644-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2018] [Accepted: 02/15/2019] [Indexed: 11/12/2022] Open
Abstract
Using first principles theory, we investigated the behavior of the one-dimensional (1D) topological edge states of high temperature superconductiviing FeSe/SrTiO3 films with Te atoms substitution to Se atoms in the bottom (top) layer in single-layer FeSe, as a function of strain. It was discovered that the 1D topological edge states are present in single-unit-cell FeSe film on SrTiO3, but are absent when more than 50% Se atoms are replaced by Te atoms. Stress induced displacive phase transformation exists in FeSe/SrTiO3 film when Te atoms substitute Se atoms in the bottom (top) layer in single-layer FeSe under 3% strain respectively. The 1D topological edge states are present under 3% (1.8%) strain in FeSe/SrTiO3 films with Te substitution Se in the bottom (top) layer in single-layer FeSe, even up to 5%, respectively. This indicates that the bonding angle of Se-Fe-Se (Te) and the distance of Te (or Se) atoms to the Fe plane are correlated with the topological edge states. Our findings provide an effective interface system that provides both superconducting and topological states, opening a new route for realizing 2D topological superconductors with proximity effect.
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Affiliation(s)
- Li Chen
- Institute of Condensed Matter Physics, Linyi University, Shandong, 276000, China.
| | - Hongmei Liu
- Institute of Condensed Matter Physics, Linyi University, Shandong, 276000, China
| | - Chuan Jiang
- Department of Data Acquisition, National Instruments, Shanghai, 201204, China
| | - Changmin Shi
- Institute of Condensed Matter Physics, Linyi University, Shandong, 276000, China
| | - Dongchao Wang
- Institute of Condensed Matter Physics, Linyi University, Shandong, 276000, China
| | - Guangliang Cui
- Institute of Condensed Matter Physics, Linyi University, Shandong, 276000, China
| | - Xiaolong Li
- Institute of Condensed Matter Physics, Linyi University, Shandong, 276000, China
| | - Qiandong Zhuang
- Physics Department, Lancaster University, Lancaster, LA1 4YB, UK
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38
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Queiroz R, Stern A. Selection Rules for Quasiparticle Interference with Internal Nonsymmorphic Symmetries. PHYSICAL REVIEW LETTERS 2018; 121:176401. [PMID: 30411964 DOI: 10.1103/physrevlett.121.176401] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/02/2018] [Revised: 08/08/2018] [Indexed: 06/08/2023]
Abstract
We study how nonsymmorphic symmetries that commute with lattice translations are reflected in the quasiparticle interference (QPI) maps measured by scanning tunneling microscopy (STM). QPI maps, which result from scattering of Bloch states off impurities, record the interference of incoming and scattered waves as a function of energy and tip's position. Although both the impurity and the tip generically break spatial symmetries, we find that the QPI maps provide universal information on these symmetries. The symmetries impose constraints on the relation between various momentum components of the Bloch functions. These relations result in selection rules on certain momentum transfers in QPI maps. We find that universal information is encoded in the absence of QPI signal, or in the relative intensity of its replications. We show examples for one-dimensional chains and an effective model of the layered compound ZrSiS. We discuss the implications of our theory in the analysis of observed QPI of the Weyl semimetal TaAs. Our theory is particularly relevant for materials in rod and layer space groups, or when a correlated order parameter, such as antiferromagnetism, enlarges the unit cell.
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Affiliation(s)
- Raquel Queiroz
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Ady Stern
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot 7610001, Israel
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39
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Wang D, Kong L, Fan P, Chen H, Zhu S, Liu W, Cao L, Sun Y, Du S, Schneeloch J, Zhong R, Gu G, Fu L, Ding H, Gao HJ. Evidence for Majorana bound states in an iron-based superconductor. Science 2018; 362:333-335. [PMID: 30115743 DOI: 10.1126/science.aao1797] [Citation(s) in RCA: 153] [Impact Index Per Article: 25.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2017] [Revised: 12/11/2017] [Accepted: 07/27/2018] [Indexed: 02/01/2023]
Abstract
The search for Majorana bound states (MBSs) has been fueled by the prospect of using their non-Abelian statistics for robust quantum computation. Two-dimensional superconducting topological materials have been predicted to host MBSs as zero-energy modes in vortex cores. By using scanning tunneling spectroscopy on the superconducting Dirac surface state of the iron-based superconductor FeTe0.55Se0.45, we observed a sharp zero-bias peak inside a vortex core that does not split when moving away from the vortex center. The evolution of the peak under varying magnetic field, temperature, and tunneling barrier is consistent with the tunneling to a nearly pure MBS, separated from nontopological bound states. This observation offers a potential platform for realizing and manipulating MBSs at a relatively high temperature.
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Affiliation(s)
- Dongfei Wang
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences (CAS), Beijing 100190, China.,School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190, China
| | - Lingyuan Kong
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences (CAS), Beijing 100190, China.,School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190, China
| | - Peng Fan
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences (CAS), Beijing 100190, China.,School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190, China
| | - Hui Chen
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences (CAS), Beijing 100190, China
| | - Shiyu Zhu
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences (CAS), Beijing 100190, China.,School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190, China
| | - Wenyao Liu
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences (CAS), Beijing 100190, China.,School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190, China
| | - Lu Cao
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences (CAS), Beijing 100190, China.,School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190, China
| | - Yujie Sun
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences (CAS), Beijing 100190, China.,CAS Center for Excellence in Topological Quantum Computation, University of Chinese Academy of Sciences, Beijing 100190, China
| | - Shixuan Du
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences (CAS), Beijing 100190, China.,CAS Center for Excellence in Topological Quantum Computation, University of Chinese Academy of Sciences, Beijing 100190, China.,Collaborative Innovation Center of Quantum Matter, Beijing 100190, China
| | - John Schneeloch
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, NY 11973, USA
| | - Ruidan Zhong
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, NY 11973, USA
| | - Genda Gu
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, NY 11973, USA
| | - Liang Fu
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Hong Ding
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences (CAS), Beijing 100190, China. .,School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190, China.,CAS Center for Excellence in Topological Quantum Computation, University of Chinese Academy of Sciences, Beijing 100190, China.,Collaborative Innovation Center of Quantum Matter, Beijing 100190, China
| | - Hong-Jun Gao
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences (CAS), Beijing 100190, China. .,School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190, China.,CAS Center for Excellence in Topological Quantum Computation, University of Chinese Academy of Sciences, Beijing 100190, China.,Collaborative Innovation Center of Quantum Matter, Beijing 100190, China
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40
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Kim S, Yi S, Oh M, Jang BG, Nam W, Yoo YC, Lee M, Jeon H, Zoh I, Lee H, Zhang C, Kim KH, Seo J, Shim JH, Chae J, Kuk Y. Surface reconstruction and charge modulation in BaFe 2As 2 superconducting film. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2018; 30:315001. [PMID: 29916822 DOI: 10.1088/1361-648x/aacd85] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Whether or not epitaxially grown superconducting films have the same bulk-like superconducting properties is an important concern. We report the structure and the electronic properties of epitaxially grown Ba(Fe1-x Co x )2As2 films using scanning tunneling microscopy and scanning tunneling spectroscopy (STS). This film showed a different surface structure, [Formula: see text]R45° reconstruction, from those of as-cleaved surfaces from bulk crystals. The electronic structure of the grown film is different from that in bulk, and it is notable that the film exhibits the same superconducting transport properties. We found that the superconducting gap at the surface is screened at the Ba layer surface in STS measurements, and the charge density wave was observed at the surface in sample in the superconducting state.
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Affiliation(s)
- S Kim
- Department of Physics and Astronomy, Seoul National University, Seoul 08826, Republic of Korea
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41
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Yoshioka K, Katayama I, Arashida Y, Ban A, Kawada Y, Konishi K, Takahashi H, Takeda J. Tailoring Single-Cycle Near Field in a Tunnel Junction with Carrier-Envelope Phase-Controlled Terahertz Electric Fields. NANO LETTERS 2018; 18:5198-5204. [PMID: 30028952 DOI: 10.1021/acs.nanolett.8b02161] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Light-field-driven processes occurring under conditions far beyond the diffraction limit of the light can be manipulated by harnessing spatiotemporally tunable near fields. A tailor-made carrier envelope phase in a tunnel junction formed between nanogap electrodes allows precisely controlled manipulation of these processes. In particular, the characterization and active control of near fields in a tunnel junction are essential for advancing elaborate manipulation of light-field-driven processes at the atomic-scale. Here, we demonstrate that desirable phase-controlled near fields can be produced in a tunnel junction via terahertz scanning tunneling microscopy (THz-STM) with a phase shifter. Measurements of the phase-resolved subcycle electron tunneling dynamics revealed an unexpected large carrier-envelope phase shift between far-field and near-field single-cycle THz waveforms. The phase shift stems from the wavelength-scale feature of the tip-sample configuration. By using a dual-phase double-pulse scheme, the electron tunneling was coherently manipulated over the femtosecond time scale. Our new prescription-in situ tailoring of single-cycle THz near fields in a tunnel junction-will offer unprecedented control of electrons for ultrafast atomic-scale electronics and metrology.
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Affiliation(s)
- Katsumasa Yoshioka
- Department of Physics, Graduate School of Engineering , Yokohama National University , Yokohama 240-8501 , Japan
| | - Ikufumi Katayama
- Department of Physics, Graduate School of Engineering , Yokohama National University , Yokohama 240-8501 , Japan
| | - Yusuke Arashida
- Department of Physics, Graduate School of Engineering , Yokohama National University , Yokohama 240-8501 , Japan
| | - Atsuhiko Ban
- Department of Physics, Graduate School of Engineering , Yokohama National University , Yokohama 240-8501 , Japan
| | - Yoichi Kawada
- Department of Physics, Graduate School of Engineering , Yokohama National University , Yokohama 240-8501 , Japan
- Central Research Laboratory , Hamamatsu Photonics K.K. , 5000 Hirakuchi, Hamakita , Hamamatsu City , Shizuoka 434-8601 , Japan
| | - Kuniaki Konishi
- Institute for Photon Science and Technology, Graduate School of Science , The University of Tokyo , Tokyo 113-0033 , Japan
| | - Hironori Takahashi
- Central Research Laboratory , Hamamatsu Photonics K.K. , 5000 Hirakuchi, Hamakita , Hamamatsu City , Shizuoka 434-8601 , Japan
| | - Jun Takeda
- Department of Physics, Graduate School of Engineering , Yokohama National University , Yokohama 240-8501 , Japan
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42
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Probing pairing symmetry in multi-band superconductors by quasiparticle interference. Sci Rep 2018; 8:11594. [PMID: 30072766 PMCID: PMC6072734 DOI: 10.1038/s41598-018-30045-0] [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: 03/28/2018] [Accepted: 07/19/2018] [Indexed: 11/08/2022] Open
Abstract
We study momentum and energy dependencies of the quasiparticle interference (QPI) response function in multiband superconductors in the framework of the strong-coupling Eliashberg approach. Within an effective two-band model we study the s± and s++ symmetry cases, corresponding to opposite or equal signs of the order parameters in the bands. We demonstrate that the momentum dependence of the QPI function is strikingly different for s± and s++ symmetries of the order parameter at energies close to the small gap. At the same time, the QPI response becomes indistinguishable for both symmetries at higher energies around the large gap. This result may guide future experiments on probing pairing symmetry in iron pnictides as well as in other unconventional superconductors.
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43
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Xie T, Wei Y, Gong D, Fennell T, Stuhr U, Kajimoto R, Ikeuchi K, Li S, Hu J, Luo H. Odd and Even Modes of Neutron Spin Resonance in the Bilayer Iron-Based Superconductor CaKFe_{4}As_{4}. PHYSICAL REVIEW LETTERS 2018; 120:267003. [PMID: 30004765 DOI: 10.1103/physrevlett.120.267003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/07/2018] [Indexed: 06/08/2023]
Abstract
We report an inelastic neutron scattering study on the spin resonance in the bilayer iron-based superconductor CaKFe_{4}As_{4}. In contrast to its quasi-two-dimensional electron structure, three strongly L-dependent modes of spin resonance are found below T_{c}=35 K. The mode energies are below and linearly scale with the total superconducting gaps summed on the nesting hole and electron pockets, essentially in agreement with the results in cuprate and heavy fermion superconductors. This observation supports the sign-reversed Cooper pairing mechanism under multiple pairing channels and resolves the long-standing puzzles concerning the broadening and dispersive spin resonance peak in iron pnictides. More importantly, the triple resonant modes can be classified into odd and even symmetries with respect to the distance of Fe-Fe planes within the Fe-As bilayer unit. Thus, our results closely resemble those in the bilayer cuprates with nondegenerate spin excitations, suggesting that these two high-T_{c} superconducting families share a common nature.
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Affiliation(s)
- Tao Xie
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yuan Wei
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Dongliang Gong
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Tom Fennell
- Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institute, CH-5232 Villigen, Switzerland
| | - Uwe Stuhr
- Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institute, CH-5232 Villigen, Switzerland
| | - Ryoichi Kajimoto
- Materials and Life Science Division, J-PARC Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195, Japan
| | - Kazuhiko Ikeuchi
- Neutron Science and Technology Center, Comprehensive Research Organization for Science and Society, Tokai, Ibaraki 319-1106, Japan
| | - Shiliang Li
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- University of Chinese Academy of Sciences, Beijing 100049, China
- Collaborative Innovation Center of Quantum Matter, Beijing 100190, China
| | - Jiangping Hu
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- University of Chinese Academy of Sciences, Beijing 100049, China
- Collaborative Innovation Center of Quantum Matter, Beijing 100190, China
| | - Huiqian Luo
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
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44
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Costanzo D, Zhang H, Reddy BA, Berger H, Morpurgo AF. Tunnelling spectroscopy of gate-induced superconductivity in MoS 2. NATURE NANOTECHNOLOGY 2018; 13:483-488. [PMID: 29713077 DOI: 10.1038/s41565-018-0122-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/27/2017] [Accepted: 03/23/2018] [Indexed: 06/08/2023]
Abstract
The ability to gate-induce superconductivity by electrostatic charge accumulation is a recent breakthrough in physics and nanoelectronics. With the exception of LaAlO3/SrTiO3 interfaces, experiments on gate-induced superconductors have been largely confined to resistance measurements, which provide very limited information about the superconducting state. Here, we explore gate-induced superconductivity in MoS2 by performing tunnelling spectroscopy to determine the energy-dependent density of states (DOS) for different levels of electron density n. In the superconducting state, the DOS is strongly suppressed at energy smaller than the gap Δ, which is maximum (Δ ~2 meV) for n of ~1 × 1014 cm-2 and decreases monotonously for larger n. A perpendicular magnetic field B generates states at E < Δ that fill the gap, but a 20% DOS suppression of superconducting origin unexpectedly persists much above the transport critical field. Conversely, an in-plane field up to 10 T leaves the DOS entirely unchanged. Our measurements exclude that the superconducting state in MoS2 is fully gapped and reveal the presence of a DOS that vanishes linearly with energy, the explanation of which requires going beyond a conventional, purely phonon-driven Bardeen-Cooper-Schrieffer mechanism.
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Affiliation(s)
| | - Haijing Zhang
- DQMP and GAP, Université de Genève, Geneva, Switzerland
| | | | - Helmuth Berger
- Institut de Physique de la Matière Complexe, Ecole Polytechnique Federale de Lausanne, Lausanne, Switzerland
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45
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Chen M, Chen X, Yang H, Du Z, Zhu X, Wang E, Wen HH. Discrete energy levels of Caroli-de Gennes-Matricon states in quantum limit in FeTe 0.55Se 0.45. Nat Commun 2018; 9:970. [PMID: 29511191 PMCID: PMC5840178 DOI: 10.1038/s41467-018-03404-8] [Citation(s) in RCA: 64] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2017] [Accepted: 02/11/2018] [Indexed: 11/13/2022] Open
Abstract
Caroli-de Gennes-Matricon (CdGM) states were predicted in 1964 as low-energy excitations within vortex cores of type-II superconductors. In the quantum limit, the energy levels of these states were predicted to be discrete with the basic levels at ±μΔ2/EF (μ = 1/2, 3/2, 5/2, …) with Δ the superconducting energy gap and EF the Fermi energy. However, due to the small ratio of Δ/EF in most type-II superconductors, it is very difficult to observe the discrete CdGM states, but rather a symmetric peak which appears at zero bias at the vortex center. Here we report the clear observation of these discrete energy levels of CdGM states in FeTe0.55Se0.45. The rather stable energies of these bound state peaks vs. space clearly validate our conclusion. Analysis based on the energies of these CdGM states indicates that the Fermi energy in the present system is very small.
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Affiliation(s)
- Mingyang Chen
- Center for Superconducting Physics and Materials, National Laboratory of Solid State Microstructures and Department of Physics, Collaborative Innovation Center for Advanced Microstructures, Nanjing University, 210093, Nanjing, China
| | - Xiaoyu Chen
- Center for Superconducting Physics and Materials, National Laboratory of Solid State Microstructures and Department of Physics, Collaborative Innovation Center for Advanced Microstructures, Nanjing University, 210093, Nanjing, China
| | - Huan Yang
- Center for Superconducting Physics and Materials, National Laboratory of Solid State Microstructures and Department of Physics, Collaborative Innovation Center for Advanced Microstructures, Nanjing University, 210093, Nanjing, China.
| | - Zengyi Du
- Center for Superconducting Physics and Materials, National Laboratory of Solid State Microstructures and Department of Physics, Collaborative Innovation Center for Advanced Microstructures, Nanjing University, 210093, Nanjing, China
| | - Xiyu Zhu
- Center for Superconducting Physics and Materials, National Laboratory of Solid State Microstructures and Department of Physics, Collaborative Innovation Center for Advanced Microstructures, Nanjing University, 210093, Nanjing, China
| | - Enyu Wang
- Center for Superconducting Physics and Materials, National Laboratory of Solid State Microstructures and Department of Physics, Collaborative Innovation Center for Advanced Microstructures, Nanjing University, 210093, Nanjing, China
| | - Hai-Hu Wen
- Center for Superconducting Physics and Materials, National Laboratory of Solid State Microstructures and Department of Physics, Collaborative Innovation Center for Advanced Microstructures, Nanjing University, 210093, Nanjing, China.
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46
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Sprau PO, Kostin A, Kreisel A, Böhmer AE, Taufour V, Canfield PC, Mukherjee S, Hirschfeld PJ, Andersen BM, Davis JCS. Discovery of orbital-selective Cooper pairing in FeSe. Science 2018; 357:75-80. [PMID: 28684522 DOI: 10.1126/science.aal1575] [Citation(s) in RCA: 236] [Impact Index Per Article: 39.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2016] [Accepted: 06/05/2017] [Indexed: 11/02/2022]
Abstract
The superconductor iron selenide (FeSe) is of intense interest owing to its unusual nonmagnetic nematic state and potential for high-temperature superconductivity. But its Cooper pairing mechanism has not been determined. We used Bogoliubov quasiparticle interference imaging to determine the Fermi surface geometry of the electronic bands surrounding the Γ = (0, 0) and X = (π/aFe, 0) points of FeSe and to measure the corresponding superconducting energy gaps. We show that both gaps are extremely anisotropic but nodeless and that they exhibit gap maxima oriented orthogonally in momentum space. Moreover, by implementing a novel technique, we demonstrate that these gaps have opposite sign with respect to each other. This complex gap configuration reveals the existence of orbital-selective Cooper pairing that, in FeSe, is based preferentially on electrons from the d yz orbitals of the iron atoms.
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Affiliation(s)
- P O Sprau
- Laboratory of Atomic and Solid State Physics, Department of Physics, Cornell University, Ithaca, NY 14853, USA.,Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, NY 11973, USA
| | - A Kostin
- Laboratory of Atomic and Solid State Physics, Department of Physics, Cornell University, Ithaca, NY 14853, USA.,Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, NY 11973, USA
| | - A Kreisel
- Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, DK 2100 Copenhagen, Denmark.,Institut für Theoretische Physik, Universität Leipzig, D-04103 Leipzig, Germany
| | - A E Böhmer
- Ames Laboratory, U.S. Department of Energy, Ames, IA 50011, USA
| | - V Taufour
- Ames Laboratory, U.S. Department of Energy, Ames, IA 50011, USA
| | - P C Canfield
- Ames Laboratory, U.S. Department of Energy, Ames, IA 50011, USA.,Department of Physics and Astronomy, Iowa State University, Ames, IA 50011, USA
| | - S Mukherjee
- Department of Physics, Binghamton University-State University of New York, Binghamton, NY, USA
| | - P J Hirschfeld
- Department of Physics, University of Florida, Gainesville, FL 32611, USA
| | - B M Andersen
- Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, DK 2100 Copenhagen, Denmark
| | - J C Séamus Davis
- Laboratory of Atomic and Solid State Physics, Department of Physics, Cornell University, Ithaca, NY 14853, USA. .,Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, NY 11973, USA.,School of Physics and Astronomy, University of St Andrews, Fife KY16 9SS, Scotland.,Tyndall National Institute, University College Cork, Cork T12R5C, Ireland
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47
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Ren M, Yan Y, Niu X, Tao R, Hu D, Peng R, Xie B, Zhao J, Zhang T, Feng DL. Superconductivity across Lifshitz transition and anomalous insulating state in surface K-dosed (Li 0.8Fe 0.2OH)FeSe. SCIENCE ADVANCES 2017; 3:e1603238. [PMID: 28740865 PMCID: PMC5510993 DOI: 10.1126/sciadv.1603238] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/21/2016] [Accepted: 05/26/2017] [Indexed: 06/07/2023]
Abstract
In iron-based superconductors, understanding the relation between superconductivity and electronic structure upon doping is crucial for exploring the pairing mechanism. Recently, it was found that, in iron selenide (FeSe), enhanced superconductivity (Tc of more than 40 K) can be achieved via electron doping, with the Fermi surface only comprising M-centered electron pockets. By using surface K dosing, scanning tunneling microscopy/spectroscopy, and angle-resolved photoemission spectroscopy, we studied the electronic structure and superconductivity of (Li0.8Fe0.2OH)FeSe in the deep electron-doped regime. We find that a Γ-centered electron band, which originally lies above the Fermi level (EF), can be continuously tuned to cross EF and contribute a new electron pocket at Γ. When this Lifshitz transition occurs, the superconductivity in the M-centered electron pocket is slightly suppressed, and a possible superconducting gap with a small size (up to ~5 meV) and a dome-like doping dependence is observed on the new Γ electron pocket. Upon further K dosing, the system eventually evolves into an insulating state. Our findings provide new clues to understand superconductivity versus Fermi surface topology and the correlation effect in FeSe-based superconductors.
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Affiliation(s)
- Mingqiang Ren
- State Key Laboratory of Surface Physics, Department of Physics, and Advanced Materials Laboratory, Fudan University, Shanghai 200433, China
| | - Yajun Yan
- State Key Laboratory of Surface Physics, Department of Physics, and Advanced Materials Laboratory, Fudan University, Shanghai 200433, China
| | - Xiaohai Niu
- State Key Laboratory of Surface Physics, Department of Physics, and Advanced Materials Laboratory, Fudan University, Shanghai 200433, China
| | - Ran Tao
- State Key Laboratory of Surface Physics, Department of Physics, and Advanced Materials Laboratory, Fudan University, Shanghai 200433, China
| | - Die Hu
- State Key Laboratory of Surface Physics, Department of Physics, and Advanced Materials Laboratory, Fudan University, Shanghai 200433, China
| | - Rui Peng
- State Key Laboratory of Surface Physics, Department of Physics, and Advanced Materials Laboratory, Fudan University, Shanghai 200433, China
| | - Binping Xie
- State Key Laboratory of Surface Physics, Department of Physics, and Advanced Materials Laboratory, Fudan University, Shanghai 200433, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing 210093, China
| | - Jun Zhao
- State Key Laboratory of Surface Physics, Department of Physics, and Advanced Materials Laboratory, Fudan University, Shanghai 200433, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing 210093, China
| | - Tong Zhang
- State Key Laboratory of Surface Physics, Department of Physics, and Advanced Materials Laboratory, Fudan University, Shanghai 200433, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing 210093, China
| | - Dong-Lai Feng
- State Key Laboratory of Surface Physics, Department of Physics, and Advanced Materials Laboratory, Fudan University, Shanghai 200433, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing 210093, China
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48
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(Li1−xFex)OHFeSe Superconductors: Crystal Growth, Structure, and Electromagnetic Properties. CRYSTALS 2017. [DOI: 10.3390/cryst7060167] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Zhou X, Eckberg C, Wilfong B, Liou SC, Vivanco HK, Paglione J, Rodriguez EE. Superconductivity and magnetism in iron sulfides intercalated by metal hydroxides. Chem Sci 2017; 8:3781-3788. [PMID: 28580110 PMCID: PMC5436553 DOI: 10.1039/c6sc05268a] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2016] [Accepted: 03/11/2017] [Indexed: 12/05/2022] Open
Abstract
Inspired by naturally occurring sulfide minerals, we present a new family of iron-based superconductors. A metastable form of FeS known as the mineral mackinawite forms two-dimensional sheets that can be readily intercalated by various cationic guest species. Under hydrothermal conditions using alkali metal hydroxides, we prepare three different cation and metal hydroxide-intercalated FeS phases including (Li1-x Fe x OH)FeS, [(Na1-x Fe x )(OH)2]FeS, and K x Fe2-y S2. Upon successful intercalation of the FeS layer, the superconducting critical temperature Tc of mackinawite is enhanced from 5 K to 8 K for the (Li1-x Fe x OH) δ+ intercalate. Layered heterostructures of [(Na1-x Fe x )(OH)2]FeS resemble the natural mineral tochilinite, which contains an iron square lattice interleaved with a hexagonal hydroxide lattice. Whilst heterostructured [(Na1-x Fe x )(OH)2]FeS displays long-range magnetic ordering near 15 K, K x Fe2-y S2 displays short range antiferromagnetism.
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Affiliation(s)
- Xiuquan Zhou
- Department of Chemistry and Biochemistry , University of Maryland , College Park , MD 20742 , USA .
- Department of Physics , University of Maryland , College Park , MD 20742 , USA
| | - Christopher Eckberg
- Department of Physics , University of Maryland , College Park , MD 20742 , USA
- Center for Nanophysics and Advanced Materials , University of Maryland , College Park , MD 20742 , USA
| | - Brandon Wilfong
- Department of Chemistry and Biochemistry , University of Maryland , College Park , MD 20742 , USA .
- Department of Physics , University of Maryland , College Park , MD 20742 , USA
| | - Sz-Chian Liou
- AIM Lab , Maryland NanoCenter , University of Maryland , College Park , MD 20742 , USA
| | - Hector K Vivanco
- Department of Chemistry and Biochemistry , University of Maryland , College Park , MD 20742 , USA .
| | - Johnpierre Paglione
- Department of Physics , University of Maryland , College Park , MD 20742 , USA
- Center for Nanophysics and Advanced Materials , University of Maryland , College Park , MD 20742 , USA
| | - Efrain E Rodriguez
- Department of Chemistry and Biochemistry , University of Maryland , College Park , MD 20742 , USA .
- Center for Nanophysics and Advanced Materials , University of Maryland , College Park , MD 20742 , USA
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Lambert F, Akbari A, Thalmeier P, Eremin I. Surface State Tunneling Signatures in the Two-Component Superconductor UPt_{3}. PHYSICAL REVIEW LETTERS 2017; 118:087004. [PMID: 28282170 DOI: 10.1103/physrevlett.118.087004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/29/2016] [Indexed: 06/06/2023]
Abstract
Quasiparticle interference (QPI) imaging of Bogoliubov excitations in quasi-two-dimensional unconventional superconductors has become a powerful technique for measuring the superconducting gap and its symmetry. Here, we present the extension of this method to three-dimensional superconductors and analyze the expected QPI spectrum for the two-component heavy-fermion superconductor UPt_{3} whose gap structure is still controversial. Starting from a 3D electronic structure and the three proposed chiral gap models E_{1g,u} or E_{2u}, we perform a slab calculation that simultaneously gives extended bulk states and topologically protected in-gap dispersionless surface states. We show that the number of Weyl arcs and their hybridization with the line node provides a fingerprint that may finally determine the true nodal structure of the UPt_{3} superconductor.
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Affiliation(s)
- Fabian Lambert
- Institut für Theoretische Physik III, Ruhr-Universität Bochum, 44801 Bochum, Germany
| | - Alireza Akbari
- Asia Pacific Center for Theoretical Physics, Pohang, Gyeongbuk 790-784, Korea and Department of Physics, and Max Planck POSTECH Center for Complex Phase Materials, POSTECH, Pohang 790-784, Korea
| | - Peter Thalmeier
- Max Planck Institute for Chemical Physics of Solids, D-01187 Dresden, Germany
| | - Ilya Eremin
- Institut für Theoretische Physik III, Ruhr-Universität Bochum, 44801 Bochum, Germany
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