1
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Aouelela M, Taha M, El-dek SI, Hassan A, Vasiliev AN, Abdel-Hafiez M. Synthesis and Characterization of Molybdenum- and Sulfur-Doped FeSe. ACS OMEGA 2023; 8:36553-36561. [PMID: 37810706 PMCID: PMC10552506 DOI: 10.1021/acsomega.3c05684] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/07/2023] [Accepted: 08/22/2023] [Indexed: 10/10/2023]
Abstract
During the past decade, two-dimensional (2D) layered materials opened novel opportunities for the exploration of exciting new physics and devices owing to their physical and electronic properties. Among 2D materials, iron selenide has attracted much attention from several physicists as they provide a fruitful stage for developing new superconductors. Chemical doping offers a powerful approach to manipulate and optimize the electronic structure and physical properties of materials. Here, to reveal how doping affects the physical properties in FeSe, we report on complementary measurements of molybdenum- and sulfur-doped FeSe with theoretical calculations. Mo0.1Fe0.9Se0.9S0.1 was synthesized by a one-step solid-state reaction method. Crystal structure and morphology were studied using powder X-ray diffraction and scanning electron microscopy. Thermal stability and decomposition behavior in doped samples were studied by thermogravimetric analysis, and to understand the microscopic influence of doping, we performed Raman spectroscopy. First-principles calculations of the electronic structure illustrate distinct changes of electronic structures of the substituted FeSe systems, which can be responsible for their superconducting properties.
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Affiliation(s)
- Marwa
H.A. Aouelela
- Materials
Science and Nanotechnology Department, Faculty of Postgraduate Studies
for Advanced Sciences, Beni-Suef University, 62511 Beni-Suef, Egypt
| | - Mohamed Taha
- Materials
Science and Nanotechnology Department, Faculty of Postgraduate Studies
for Advanced Sciences, Beni-Suef University, 62511 Beni-Suef, Egypt
| | - Samaa I. El-dek
- Materials
Science and Nanotechnology Department, Faculty of Postgraduate Studies
for Advanced Sciences, Beni-Suef University, 62511 Beni-Suef, Egypt
| | - Abdelwahab Hassan
- Department
of Physics, Faculty of Science, Fayoum University, 63514 Fayoum, Egypt
| | - Alexander N. Vasiliev
- National
University of Science and Technology MISiS, 119049 Moscow, Russia
- Lomonosov
Moscow State University, 119991 Moscow, Russia
| | - Mahmoud Abdel-Hafiez
- Department
of Physics and Astronomy, Uppsala University, Box 516, SE-75120 Uppsala, Sweden
- Department
of Applied Physics and Astronomy, University
of Sharjah, P. O. Box 27272 Sharjah, United Arab Emirates
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2
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Matsuura K, Roppongi M, Qiu M, Sheng Q, Cai Y, Yamakawa K, Guguchia Z, Day RP, Kojima KM, Damascelli A, Sugimura Y, Saito M, Takenaka T, Ishihara K, Mizukami Y, Hashimoto K, Gu Y, Guo S, Fu L, Zhang Z, Ning F, Zhao G, Dai G, Jin C, Beare JW, Luke GM, Uemura YJ, Shibauchi T. Two superconducting states with broken time-reversal symmetry in FeSe 1-xS x. Proc Natl Acad Sci U S A 2023; 120:e2208276120. [PMID: 37186859 PMCID: PMC10214191 DOI: 10.1073/pnas.2208276120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2022] [Accepted: 04/12/2023] [Indexed: 05/17/2023] Open
Abstract
Iron-chalcogenide superconductors FeSe1-xSx possess unique electronic properties such as nonmagnetic nematic order and its quantum critical point. The nature of superconductivity with such nematicity is important for understanding the mechanism of unconventional superconductivity. A recent theory suggested the possible emergence of a fundamentally new class of superconductivity with the so-called Bogoliubov Fermi surfaces (BFSs) in this system. However, such an ultranodal pair state requires broken time-reversal symmetry (TRS) in the superconducting state, which has not been observed experimentally. Here, we report muon spin relaxation (μSR) measurements in FeSe1-xSx superconductors for 0 ≤ x ≤ 0.22 covering both orthorhombic (nematic) and tetragonal phases. We find that the zero-field muon relaxation rate is enhanced below the superconducting transition temperature Tc for all compositions, indicating that the superconducting state breaks TRS both in the nematic and tetragonal phases. Moreover, the transverse-field μSR measurements reveal that the superfluid density shows an unexpected and substantial reduction in the tetragonal phase (x > 0.17). This implies that a significant fraction of electrons remain unpaired in the zero-temperature limit, which cannot be explained by the known unconventional superconducting states with point or line nodes. The TRS breaking and the suppressed superfluid density in the tetragonal phase, together with the reported enhanced zero-energy excitations, are consistent with the ultranodal pair state with BFSs. The present results reveal two different superconducting states with broken TRS separated by the nematic critical point in FeSe1-xSx, which calls for the theory of microscopic origins that account for the relation between nematicity and superconductivity.
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Affiliation(s)
- Kohei Matsuura
- Department of Advanced Materials Science, University of Tokyo, Kashiwa277-8561, Japan
| | - Masaki Roppongi
- Department of Advanced Materials Science, University of Tokyo, Kashiwa277-8561, Japan
| | - Mingwei Qiu
- Department of Advanced Materials Science, University of Tokyo, Kashiwa277-8561, Japan
| | - Qi Sheng
- Department of Physics, Columbia University, New York, NY10027
| | - Yipeng Cai
- Quantum Matter Institute, University of British Columbia, Vancouver, BCV6T 1Z4, Canada
- Department of Physics & Astronomy, University of British Columbia, Vancouver, BCV6T 1Z1, Canada
| | | | - Zurab Guguchia
- Department of Physics, Columbia University, New York, NY10027
| | - Ryan P. Day
- Quantum Matter Institute, University of British Columbia, Vancouver, BCV6T 1Z4, Canada
- Department of Physics & Astronomy, University of British Columbia, Vancouver, BCV6T 1Z1, Canada
| | - Kenji M. Kojima
- Quantum Matter Institute, University of British Columbia, Vancouver, BCV6T 1Z4, Canada
- Centre for Molecular and Materials Science, TRIUMF, Vancouver, BCV6T 2A3, Canada
| | - Andrea Damascelli
- Quantum Matter Institute, University of British Columbia, Vancouver, BCV6T 1Z4, Canada
- Department of Physics & Astronomy, University of British Columbia, Vancouver, BCV6T 1Z1, Canada
| | - Yuichi Sugimura
- Department of Advanced Materials Science, University of Tokyo, Kashiwa277-8561, Japan
| | - Mikihiko Saito
- Department of Advanced Materials Science, University of Tokyo, Kashiwa277-8561, Japan
| | - Takaaki Takenaka
- Department of Advanced Materials Science, University of Tokyo, Kashiwa277-8561, Japan
| | - Kota Ishihara
- Department of Advanced Materials Science, University of Tokyo, Kashiwa277-8561, Japan
| | - Yuta Mizukami
- Department of Advanced Materials Science, University of Tokyo, Kashiwa277-8561, Japan
| | - Kenichiro Hashimoto
- Department of Advanced Materials Science, University of Tokyo, Kashiwa277-8561, Japan
| | - Yilun Gu
- Department of Physics, Zhejiang University, Hangzhou310027, China
| | - Shengli Guo
- Department of Physics, Zhejiang University, Hangzhou310027, China
| | - Licheng Fu
- Department of Physics, Zhejiang University, Hangzhou310027, China
| | - Zheneng Zhang
- Department of Physics, Zhejiang University, Hangzhou310027, China
| | - Fanlong Ning
- Department of Physics, Zhejiang University, Hangzhou310027, China
| | - Guoqiang Zhao
- Beijing National Laboratory for Condensed Matter Physics, Beijing100190, China
- Institute of Physics, Chinese Academy of Sciences, Beijing100190, China
- University of Chinese Academy of Sciences, Beijing100190, China
| | - Guangyang Dai
- Beijing National Laboratory for Condensed Matter Physics, Beijing100190, China
- Institute of Physics, Chinese Academy of Sciences, Beijing100190, China
- University of Chinese Academy of Sciences, Beijing100190, China
| | - Changqing Jin
- Beijing National Laboratory for Condensed Matter Physics, Beijing100190, China
- Institute of Physics, Chinese Academy of Sciences, Beijing100190, China
- University of Chinese Academy of Sciences, Beijing100190, China
| | - James W. Beare
- Department of Physics and Astronomy, McMaster University, Hamilton, ONL8S 4M1, Canada
| | - Graeme M. Luke
- Centre for Molecular and Materials Science, TRIUMF, Vancouver, BCV6T 2A3, Canada
- Department of Physics and Astronomy, McMaster University, Hamilton, ONL8S 4M1, Canada
| | | | - Takasada Shibauchi
- Department of Advanced Materials Science, University of Tokyo, Kashiwa277-8561, Japan
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3
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Song Y, Chen Z, Zhang Q, Xu H, Lou X, Chen X, Xu X, Zhu X, Tao R, Yu T, Ru H, Wang Y, Zhang T, Guo J, Gu L, Xie Y, Peng R, Feng D. High temperature superconductivity at FeSe/LaFeO 3 interface. Nat Commun 2021; 12:5926. [PMID: 34635672 PMCID: PMC8505662 DOI: 10.1038/s41467-021-26201-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2021] [Accepted: 09/15/2021] [Indexed: 11/09/2022] Open
Abstract
Enormous enhancement of superconducting pairing temperature (Tg) to 65 K in FeSe/SrTiO3 has made it a spotlight. Despite the effort of interfacial engineering, FeSe interfaced with TiOx remains the unique case in hosting high Tg, hindering a decisive understanding on the general mechanism and ways to further improving Tg. Here we constructed a new high-Tg interface, single-layer FeSe interfaced with FeOx-terminated LaFeO3. Large superconducting gap and diamagnetic response evidence that the superconducting pairing can emerge near 80 K, highest amongst all-known interfacial superconductors. Combining various techniques, we reveal interfacial charge transfer and strong interfacial electron-phonon coupling (EPC) in FeSe/LaFeO3, showing that the cooperative pairing mechanism works beyond FeSe-TiOx. Intriguingly, the stronger interfacial EPC than that in FeSe/SrTiO3 is likely induced by the stronger interfacial bonding in FeSe/LaFeO3, and can explain the higher Tg according to recent theoretical calculations, pointing out a workable route in designing new interfaces to achieve higher Tg.
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Affiliation(s)
- Yuanhe Song
- Laboratory of Advanced Materials, State Key Laboratory of Surface Physics, and Department of Physics, Fudan University, 200438, Shanghai, China
| | - Zheng Chen
- Department of Physics, Zhejiang University, 310027, Hangzhou, China
| | - Qinghua Zhang
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, 100190, Beijing, China
| | - Haichao Xu
- Laboratory of Advanced Materials, State Key Laboratory of Surface Physics, and Department of Physics, Fudan University, 200438, Shanghai, China
- Shanghai Research Center for Quantum Sciences, 201315, Shanghai, China
| | - Xia Lou
- Laboratory of Advanced Materials, State Key Laboratory of Surface Physics, and Department of Physics, Fudan University, 200438, Shanghai, China
| | - Xiaoyang Chen
- Laboratory of Advanced Materials, State Key Laboratory of Surface Physics, and Department of Physics, Fudan University, 200438, Shanghai, China
| | - Xiaofeng Xu
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, 100190, Beijing, China
| | - Xuetao Zhu
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, 100190, Beijing, China
| | - Ran Tao
- Laboratory of Advanced Materials, State Key Laboratory of Surface Physics, and Department of Physics, Fudan University, 200438, Shanghai, China
| | - Tianlun Yu
- Laboratory of Advanced Materials, State Key Laboratory of Surface Physics, and Department of Physics, Fudan University, 200438, Shanghai, China
| | - Hao Ru
- Laboratory of Advanced Materials, State Key Laboratory of Surface Physics, and Department of Physics, Fudan University, 200438, Shanghai, China
| | - Yihua Wang
- Laboratory of Advanced Materials, State Key Laboratory of Surface Physics, and Department of Physics, Fudan University, 200438, Shanghai, China
- Shanghai Research Center for Quantum Sciences, 201315, Shanghai, China
| | - Tong Zhang
- Laboratory of Advanced Materials, State Key Laboratory of Surface Physics, and Department of Physics, Fudan University, 200438, Shanghai, China
- Shanghai Research Center for Quantum Sciences, 201315, Shanghai, China
| | - Jiandong Guo
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, 100190, Beijing, China.
| | - Lin Gu
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, 100190, Beijing, China.
| | - Yanwu Xie
- Department of Physics, Zhejiang University, 310027, Hangzhou, China.
| | - Rui Peng
- Laboratory of Advanced Materials, State Key Laboratory of Surface Physics, and Department of Physics, Fudan University, 200438, Shanghai, China.
- Shanghai Research Center for Quantum Sciences, 201315, Shanghai, China.
| | - Donglai Feng
- Shanghai Research Center for Quantum Sciences, 201315, Shanghai, China.
- Hefei National Laboratory for Physical Science at Microscale and Department of Physics, University of Science and Technology of China, 230026, Hefei, Anhui, China.
- Collaborative Innovation Center of Advanced Microstructures, 210093, Nanjing, China.
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4
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Quadrupolar charge dynamics in the nonmagnetic FeSe 1-x S x superconductors. Proc Natl Acad Sci U S A 2021; 118:2020585118. [PMID: 33980712 DOI: 10.1073/pnas.2020585118] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
We use polarization-resolved electronic Raman spectroscopy to study quadrupolar charge dynamics in a nonmagnetic [Formula: see text] superconductor. We observe two types of long-wavelength [Formula: see text] symmetry excitations: 1) a low-energy quasi-elastic scattering peak (QEP) and 2) a broad electronic continuum with a maximum at 55 meV. Below the tetragonal-to-orthorhombic structural transition at [Formula: see text], a pseudogap suppression with temperature dependence reminiscent of the nematic order parameter develops in the [Formula: see text] symmetry spectra of the electronic excitation continuum. The QEP exhibits critical enhancement upon cooling toward [Formula: see text] The intensity of the QEP grows with increasing sulfur concentration x and maximizes near critical concentration [Formula: see text], while the pseudogap size decreases with the suppression of [Formula: see text] We interpret the development of the pseudogap in the quadrupole scattering channel as a manifestation of transition from the non-Fermi liquid regime, dominated by strong Pomeranchuk-like fluctuations giving rise to intense electronic continuum of excitations in the fourfold symmetric high-temperature phase, to the Fermi liquid regime in the broken-symmetry nematic phase where the quadrupole fluctuations are suppressed.
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5
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Bu K, Zhang W, Fei Y, Zheng Y, Ai F, Wu Z, Wang Q, Wo H, Zhao J, Yin Y. Observation of an electronic order along [110] direction in FeSe. Nat Commun 2021; 12:1385. [PMID: 33654059 PMCID: PMC7925548 DOI: 10.1038/s41467-021-21318-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2019] [Accepted: 01/17/2021] [Indexed: 11/30/2022] Open
Abstract
Multiple ordered states have been observed in unconventional superconductors. Here, we apply scanning tunneling microscopy to probe the intrinsic ordered states in FeSe, the structurally simplest iron-based superconductor. Besides the well-known nematic order along [100] direction, we observe a checkerboard charge order in the iron lattice, which we name a [110] electronic order in FeSe. The [110] electronic order is robust at 77 K, accompanied with the rather weak [100] nematic order. At 4.5 K, The [100] nematic order is enhanced, while the [110] electronic order forms domains with reduced correlation length. In addition, the collective [110] order is gaped around [−40, 40] meV at 4.5 K. The observation of this exotic electronic order may shed new light on the origin of the ordered states in FeSe. Understanding the relation of different electronic orders in high temperature superconductors is of fundamental interest. Here, the authors observe a checkerboard charge order along [110] direction of FeSe.
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Affiliation(s)
- Kunliang Bu
- Zhejiang Province Key Laboratory of Quantum Technology and Device, Department of Physics, Zhejiang University, Hangzhou, China
| | - Wenhao Zhang
- Zhejiang Province Key Laboratory of Quantum Technology and Device, Department of Physics, Zhejiang University, Hangzhou, China
| | - Ying Fei
- Zhejiang Province Key Laboratory of Quantum Technology and Device, Department of Physics, Zhejiang University, Hangzhou, China
| | - Yuan Zheng
- Zhejiang Province Key Laboratory of Quantum Technology and Device, Department of Physics, Zhejiang University, Hangzhou, China
| | - Fangzhou Ai
- Zhejiang Province Key Laboratory of Quantum Technology and Device, Department of Physics, Zhejiang University, Hangzhou, China
| | - Zongxiu Wu
- Zhejiang Province Key Laboratory of Quantum Technology and Device, Department of Physics, Zhejiang University, Hangzhou, China
| | - Qisi Wang
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai, China
| | - Hongliang Wo
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai, China
| | - Jun Zhao
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai, China.,Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, China
| | - Yi Yin
- Zhejiang Province Key Laboratory of Quantum Technology and Device, Department of Physics, Zhejiang University, Hangzhou, China. .,Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, China.
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6
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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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7
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Kasahara S, Sato Y, Licciardello S, Čulo M, Arsenijević S, Ottenbros T, Tominaga T, Böker J, Eremin I, Shibauchi T, Wosnitza J, Hussey NE, Matsuda Y. Evidence for an Fulde-Ferrell-Larkin-Ovchinnikov State with Segmented Vortices in the BCS-BEC-Crossover Superconductor FeSe. PHYSICAL REVIEW LETTERS 2020; 124:107001. [PMID: 32216412 DOI: 10.1103/physrevlett.124.107001] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/19/2019] [Accepted: 02/05/2020] [Indexed: 06/10/2023]
Abstract
We present resistivity and thermal-conductivity measurements of superconducting FeSe in intense magnetic fields up to 35 T applied parallel to the ab plane. At low temperatures, the upper critical field μ_{0}H_{c2}^{ab} shows an anomalous upturn, while thermal conductivity exhibits a discontinuous jump at μ_{0}H^{*}≈24 T well below μ_{0}H_{c2}^{ab}, indicating a first-order phase transition in the superconducting state. This demonstrates the emergence of a distinct field-induced superconducting phase. Moreover, the broad resistive transition at high temperatures abruptly becomes sharp upon entering the high-field phase, indicating a dramatic change of the magnetic-flux properties. We attribute the high-field phase to the Fulde-Ferrel-Larkin-Ovchinnikov (FFLO) state, where the formation of planar nodes gives rise to a segmentation of the flux-line lattice. We point out that strongly orbital-dependent pairing as well as spin-orbit interactions, the multiband nature, and the extremely small Fermi energy are important for the formation of the FFLO state in FeSe.
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Affiliation(s)
- S Kasahara
- Department of Physics, Kyoto University, Kyoto 606-8502 Japan
| | - Y Sato
- Department of Physics, Kyoto University, Kyoto 606-8502 Japan
| | - S Licciardello
- High Field Magnet Laboratory (HFML-EMFL) and Institute for Molecules and Materials, Radboud University, 6525 ED Nijmegen, The Netherlands
| | - M Čulo
- High Field Magnet Laboratory (HFML-EMFL) and Institute for Molecules and Materials, Radboud University, 6525 ED Nijmegen, The Netherlands
| | - S Arsenijević
- Hochfeld-Magnetlabor Dresden (HLD-EMFL) and Würzburg-Dresden Cluster of Excellence ct.qmat, Helmholtz-Zentrum Dresden-Rossendorf, D-01328 Dresden, Germany
| | - T Ottenbros
- High Field Magnet Laboratory (HFML-EMFL) and Institute for Molecules and Materials, Radboud University, 6525 ED Nijmegen, The Netherlands
| | - T Tominaga
- Department of Physics, Kyoto University, Kyoto 606-8502 Japan
| | - J Böker
- Institut für Theoretische Physik III, Ruhr-Universität Bochum, D-44801 Bochum, Germany
| | - I Eremin
- Institut für Theoretische Physik III, Ruhr-Universität Bochum, D-44801 Bochum, Germany
- National University of Science and Technology MISiS, 119049 Moscow, Russian Federation
| | - T Shibauchi
- Department of Advanced Materials Science, University of Tokyo, Chiba 277-8561, Japan
| | - J Wosnitza
- Hochfeld-Magnetlabor Dresden (HLD-EMFL) and Würzburg-Dresden Cluster of Excellence ct.qmat, Helmholtz-Zentrum Dresden-Rossendorf, D-01328 Dresden, Germany
- Institut für Festkörper- und Materialphysik, Technische Universität Dresden, 01062 Dresden, Germany
| | - N E Hussey
- High Field Magnet Laboratory (HFML-EMFL) and Institute for Molecules and Materials, Radboud University, 6525 ED Nijmegen, The Netherlands
- H.H. Wills Physics Laboratory, University of Bristol, Tyndall Avenue, BS8 1TL, United Kingdom
| | - Y Matsuda
- Department of Physics, Kyoto University, Kyoto 606-8502 Japan
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8
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Topological ultranodal pair states in iron-based superconductors. Nat Commun 2020; 11:523. [PMID: 31988317 PMCID: PMC6985224 DOI: 10.1038/s41467-020-14357-2] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2019] [Accepted: 12/19/2019] [Indexed: 11/09/2022] Open
Abstract
Bogoliubov Fermi surfaces are contours of zero-energy excitations that are protected in the superconducting state. Here we show that multiband superconductors with dominant spin singlet, intraband pairing of spin-1/2 electrons can undergo a transition to a state with Bogoliubov Fermi surfaces if spin-orbit coupling, interband pairing and time reversal symmetry breaking are also present. These latter effects may be small, but drive the transition to the topological state for appropriate nodal structure of the intra-band pair. Such a state should display nonzero zero-bias density of states and corresponding residual Sommerfeld coefficient as for a disordered nodal superconductor, but occurring even in the pure case. We present a model appropriate for iron-based superconductors where the topological transition associated with creation of a Bogoliubov Fermi surface can be studied. The model gives results that strongly resemble experiments on FeSe1−xSx across the nematic transition, where this ultranodal behavior may already have been observed. Experiments indicate an abrupt change in the pairing gap near the nematic transition in the FeSe1−xSx iron-based superconductor. Here, Setty et al. propose to explain them via a novel spin-1/2 paired state with topologically protected zero-energy excitations over a finite area nodal surface.
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9
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Rhodes LC, Watson MD, Kim TK, Eschrig M. k_{z} Selective Scattering within Quasiparticle Interference Measurements of FeSe. PHYSICAL REVIEW LETTERS 2019; 123:216404. [PMID: 31809140 DOI: 10.1103/physrevlett.123.216404] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/05/2019] [Revised: 09/09/2019] [Indexed: 06/10/2023]
Abstract
Quasiparticle interference (QPI) provides a wealth of information relating to the electronic structure of a material. However, it is often assumed that this information is constrained to two-dimensional electronic states. We show that this is not necessarily the case. For FeSe, a system dominated by surface defects, we show that it is actually all electronic states with negligible group velocity in the z axis that are contained within the experimental data. By using a three-dimensional tight-binding model of FeSe, fit to photoemission measurements, we directly reproduce the experimental QPI scattering dispersion, within a T-matrix formalism, by including both k_{z}=0 and k_{z}=π electronic states. This result unifies both tunnelling based and photoemission based experiments on FeSe and highlights the importance of k_{z} within surface sensitive measurements of QPI.
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Affiliation(s)
- Luke C Rhodes
- Department of Physics, Royal Holloway, University of London, Egham, Surrey TW20 0EX, United Kingdom
- Diamond Light Source, Harwell Campus, Didcot OX11 0DE, United Kingdom
- School of Physics and Astronomy, University of St. Andrews, St. Andrews KY16 9SS, United Kingdom
| | - Matthew D Watson
- School of Physics and Astronomy, University of St. Andrews, St. Andrews KY16 9SS, United Kingdom
| | - Timur K Kim
- Diamond Light Source, Harwell Campus, Didcot OX11 0DE, United Kingdom
| | - Matthias Eschrig
- Department of Physics, Royal Holloway, University of London, Egham, Surrey TW20 0EX, United Kingdom
- Institute of Physics, University of Greifswald, Felix-Hausdorff-Strasse 6, 17489 Greifswald, Germany
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10
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Evidence of cooperative effect on the enhanced superconducting transition temperature at the FeSe/SrTiO 3 interface. Nat Commun 2019; 10:758. [PMID: 30770805 PMCID: PMC6377624 DOI: 10.1038/s41467-019-08560-z] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2018] [Accepted: 01/18/2019] [Indexed: 11/16/2022] Open
Abstract
At the interface between monolayer FeSe films and SrTiO3 substrates the superconducting transition temperature (Tc) is unexpectedly high, triggering a surge of excitement. The mechanism for the Tc enhancement has been the central question, as it may present a new strategy for seeking out higher Tc materials. To reveal this enigmatic mechanism, by combining advances in high quality interface growth, 16O \documentclass[12pt]{minimal}
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\begin{document}$$\leftrightarrow$$\end{document}↔18O isotope substitution, and extensive data from angle resolved photoemission spectroscopy, we provide striking evidence that the high Tc in FeSe/SrTiO3 is the cooperative effect of the intrinsic pairing mechanism in the FeSe and interactions between the FeSe electrons and SrTiO3 phonons. Furthermore, our results point to the promising prospect that similar cooperation between different Cooper pairing channels may be a general framework to understand and design high-temperature superconductors. The mechanism of enhanced superconducting transition temperature (Tc) at the FeSe/SrTiO3 interface remains enigmatic. Here, Song and Yu et al. reveal the evidence of cooperation between intrinsic pairing interaction in FeSe and interfacial electron–phonon coupling to enhance the Tc at the FeSe/SrTiO3 interface.
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11
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Miao J, Niu X, Jiang J, Peng R, Xie B, Chen F, Xu H, Feng D. Enhanced superconductivity of Ba 0.5K 0.5Fe 2As 2 under surface potassium dosing. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2018; 30:455601. [PMID: 30251965 DOI: 10.1088/1361-648x/aae423] [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
Surface potassium dosing has been proven to be an effective method in tuning the electron doping and enhancing the superconducting transition temperatures in both iron chalcogenides and electron doped iron pnictides. However, it is not clear how surface potassium dosing affects the hole doping and superconductivity in hole doped Fe-based superconductors. Here we performed K-dosing on Ba0.5K0.5Fe2As2, a prototypical hole-doped iron pnictide compound, and explored the electronic structure by in situ angle-resolved photoemission spectroscopy measurements. Starting from the slightly over-doped Ba0.5K0.5Fe2As2, surface K-dosing effectively reduces the hole concentration towards optimal doping and enhances the superconductivity. Intriguingly, the enhancement of superconductivity does not slow down at optimal doping, and the gap further increases with K dosing even when the carrier doping effect is saturated. Meanwhile, the quasiparticle coherence of the inner hole pockets is enhanced by higher K dosing. Our results uncover a novel scattering-reduction effect of K-dosing in Ba1-x K x Fe2As2, which collaborates with the carrier doping effect and enhances superconductivity.
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Affiliation(s)
- Jin Miao
- State Key Laboratory of Surface Physics, Department of Physics, and Laboratory of Advanced Materials, Fudan University, Shanghai 200433, People's Republic of China. Collaborative Innovation Center of Advanced Microstructures, Nanjing 210093, People's Republic of China
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12
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Kang J, Fernandes RM, Chubukov A. Superconductivity in FeSe: The Role of Nematic Order. PHYSICAL REVIEW LETTERS 2018; 120:267001. [PMID: 30004771 DOI: 10.1103/physrevlett.120.267001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/03/2018] [Indexed: 06/08/2023]
Abstract
Bulk FeSe is a special iron-based material in which superconductivity emerges inside a well-developed nematic phase. We present a microscopic model for this nematic superconducting state, which takes into account the mixing between s-wave and d-wave pairing channels and the changes in the orbital spectral weight promoted by the sign-changing nematic order parameter. We show that nematicity only weakly affects T_{c}, but gives rise to cos2θ variation of the pairing gap on the hole pocket, whose magnitude and size agrees with angle resolved photoemission spectroscopy and STM data. We further show that nematicity increases the weight of the d_{xz} orbital on the hole pocket, and increases (reduces) the weight of the d_{xy} orbital on the Y (X) electron pocket.
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Affiliation(s)
- Jian Kang
- National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32304, USA
| | - Rafael M Fernandes
- School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota 55455, USA
| | - Andrey Chubukov
- School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota 55455, USA
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13
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Hanaguri T, Iwaya K, Kohsaka Y, Machida T, Watashige T, Kasahara S, Shibauchi T, Matsuda Y. Two distinct superconducting pairing states divided by the nematic end point in FeSe 1-x S x. SCIENCE ADVANCES 2018; 4:eaar6419. [PMID: 29806028 PMCID: PMC5969813 DOI: 10.1126/sciadv.aar6419] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/01/2017] [Accepted: 04/12/2018] [Indexed: 06/08/2023]
Abstract
Unconventional superconductivity often competes or coexists with other electronic orders. In iron-based superconductors, a central issue has been the relationship between superconductivity and electronic nematicity, spontaneous breaking of the lattice rotational symmetry. Using spectroscopic-imaging scanning tunneling microscopy, we simultaneously investigated the electronic structure and the superconducting gap in FeSe1-x S x , where the nematicity diminishes above the nematic end point (NEP) at x = 0.17. The nematic band structure appears as anisotropic quasiparticle-interference patterns that gradually become isotropic with increasing x without anomalies at the NEP. By contrast, the superconducting gap, which is intact in the nematic phase, discontinuously shrinks above the NEP. This implies that the presence or absence of nematicity results in two distinct pairing states, whereas the pairing interaction is insensitive to the strength of nematicity.
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Affiliation(s)
- Tetsuo Hanaguri
- RIKEN Center for Emergent Matter Science, Wako, Saitama 351-0198, Japan
| | - Katsuya Iwaya
- RIKEN Center for Emergent Matter Science, Wako, Saitama 351-0198, Japan
| | - Yuhki Kohsaka
- RIKEN Center for Emergent Matter Science, Wako, Saitama 351-0198, Japan
| | - Tadashi Machida
- RIKEN Center for Emergent Matter Science, Wako, Saitama 351-0198, Japan
| | | | | | - Takasada Shibauchi
- Department of Advanced Materials Science, University of Tokyo, Chiba 277-8561, Japan
| | - Yuji Matsuda
- Department of Physics, Kyoto University, Kyoto 606-8502, Japan
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14
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Sato Y, Kasahara S, Taniguchi T, Xing X, Kasahara Y, Tokiwa Y, Yamakawa Y, Kontani H, Shibauchi T, Matsuda Y. Abrupt change of the superconducting gap structure at the nematic critical point in FeSe 1-xS x. Proc Natl Acad Sci U S A 2018; 115:1227-1231. [PMID: 29363600 PMCID: PMC5819433 DOI: 10.1073/pnas.1717331115] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The emergence of the nematic electronic state that breaks rotational symmetry is one of the most fascinating properties of the iron-based superconductors, and has relevance to cuprates as well. FeSe has a unique ground state in which superconductivity coexists with a nematic order without long-range magnetic ordering, providing a significant opportunity to investigate the role of nematicity in the superconducting pairing interaction. Here, to reveal how the superconducting gap evolves with nematicity, we measure the thermal conductivity and specific heat of FeSe1 - x S x , in which the nematicity is suppressed by isoelectronic sulfur substitution and a nematic critical point (NCP) appears at [Formula: see text] We find that, in the whole nematic regime ([Formula: see text]), the field dependence of two quantities consistently shows two-gap behavior; one gap is small but highly anisotropic with deep minima or line nodes, and the other is larger and more isotropic. In stark contrast, in the tetragonal regime ([Formula: see text]), the larger gap becomes strongly anisotropic, demonstrating an abrupt change in the superconducting gap structure at the NCP. Near the NCP, charge fluctuations of [Formula: see text] and [Formula: see text] orbitals are enhanced equally in the tetragonal side, whereas they develop differently in the orthorhombic side. Our observation therefore directly implies that the orbital-dependent nature of the nematic fluctuations has a strong impact on the superconducting gap structure and hence on the pairing interaction.
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Affiliation(s)
- Yuki Sato
- Department of Physics, Kyoto University, Kyoto 606-8502, Japan
| | | | | | - Xiangzhuo Xing
- Department of Physics, Kyoto University, Kyoto 606-8502, Japan
| | - Yuichi Kasahara
- Department of Physics, Kyoto University, Kyoto 606-8502, Japan
| | - Yoshifumi Tokiwa
- Center for Electronic Correlations and Magnetism, Institute of Physics, Augsburg University, 86159 Augsburg, Germany
| | - Youichi Yamakawa
- Department of Physics, Nagoya University, Nagoya 464-8602, Japan
| | - Hiroshi Kontani
- Department of Physics, Nagoya University, Nagoya 464-8602, Japan
| | - Takasada Shibauchi
- Department of Advanced Materials Science, University of Tokyo, Chiba 277-8561, Japan
| | - Yuji Matsuda
- Department of Physics, Kyoto University, Kyoto 606-8502, Japan;
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15
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Hashimoto T, Ota Y, Yamamoto HQ, Suzuki Y, Shimojima T, Watanabe S, Chen C, Kasahara S, Matsuda Y, Shibauchi T, Okazaki K, Shin S. Superconducting gap anisotropy sensitive to nematic domains in FeSe. Nat Commun 2018; 9:282. [PMID: 29348671 PMCID: PMC5773685 DOI: 10.1038/s41467-017-02739-y] [Citation(s) in RCA: 47] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2017] [Accepted: 12/20/2017] [Indexed: 11/29/2022] Open
Abstract
The structure of the superconducting gap in unconventional superconductors holds a key to understand the momentum-dependent pairing interactions. In superconducting FeSe, there have been controversial results reporting nodal and nodeless gap structures, raising a fundamental issue of pairing mechanisms of iron-based superconductivity. Here, by utilizing polarization-dependent laser-excited angle-resolved photoemission spectroscopy, we report a detailed momentum dependence of the gap in single- and multi-domain regions of orthorhombic FeSe crystals. We confirm that the superconducting gap has a twofold in-plane anisotropy, associated with the nematicity due to orbital ordering. In twinned regions, we clearly find finite gap minima near the vertices of the major axis of the elliptical zone-centered Fermi surface, indicating a nodeless state. In contrast, the single-domain gap drops steeply to zero in a narrow angle range, evidencing for nascent nodes. Such unusual node lifting in multi-domain regions can be explained by the nematicity-induced time-reversal symmetry breaking near the twin boundaries. The superconducting gap structure of FeSe remains a debated issue. Here, Hashimoto et al. report momentum dependence of the gap in single- and multi-domain regions of orthorhombic FeSe crystals, revealing an unusual node lifting of the gap structure in multi-domain regions.
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Affiliation(s)
- Takahiro Hashimoto
- Institute for Solid State Physics (ISSP), University of Tokyo, Kashiwa, Chiba, 277-8581, Japan
| | - Yuichi Ota
- Institute for Solid State Physics (ISSP), University of Tokyo, Kashiwa, Chiba, 277-8581, Japan
| | - Haruyoshi Q Yamamoto
- Institute for Solid State Physics (ISSP), University of Tokyo, Kashiwa, Chiba, 277-8581, Japan
| | - Yuya Suzuki
- Quantum-Phase Electronics Center (QPEC) and Department of Applied Physics, University of Tokyo, Bunkyo, Tokyo, 113-8656, Japan
| | - Takahiro Shimojima
- Quantum-Phase Electronics Center (QPEC) and Department of Applied Physics, University of Tokyo, Bunkyo, Tokyo, 113-8656, Japan
| | - Shuntaro Watanabe
- Research Institute for Science and Technology, Tokyo University of Science, Chiba, 278-8510, Japan
| | - Chuangtian Chen
- Beijing Center for Crystal R&D, Chinese Academy of Science (CAS), Zhongguancun, Beijing, 100190, China
| | | | - Yuji Matsuda
- Department of Physics, Kyoto University, Kyoto, 606-8502, Japan
| | - Takasada Shibauchi
- Department of Advanced Materials Science, University of Tokyo, Kashiwa, Chiba, 277-8561, Japan
| | - Kozo Okazaki
- Institute for Solid State Physics (ISSP), University of Tokyo, Kashiwa, Chiba, 277-8581, Japan.
| | - Shik Shin
- Institute for Solid State Physics (ISSP), University of Tokyo, Kashiwa, Chiba, 277-8581, Japan.
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16
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Böhmer AE, Kreisel A. Nematicity, magnetism and superconductivity in FeSe. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2018; 30:023001. [PMID: 29240560 DOI: 10.1088/1361-648x/aa9caa] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Iron-based superconductors are well known for their complex interplay between structure, magnetism and superconductivity. FeSe offers a particularly fascinating example. This material has been intensely discussed because of its extended nematic phase, whose relationship with magnetism is not obvious. Superconductivity in FeSe is highly tunable, with the superconducting transition temperature, T c, ranging from 8 K in bulk single crystals at ambient pressure to almost 40 K under pressure or in intercalated systems, and to even higher temperatures in thin films. In this topical review, we present an overview of nematicity, magnetism and superconductivity, and discuss the interplay of these phases in FeSe. We focus on bulk FeSe and the effects of physical pressure and chemical substitutions as tuning parameters. The experimental results are discussed in the context of the well-studied iron-pnictide superconductors and interpretations from theoretical approaches are presented.
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Affiliation(s)
- Anna E Böhmer
- Ames Laboratory, US DOE, Ames, IA 50011, United States of America
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17
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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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18
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Chareev D, Ovchenkov Y, Shvanskaya L, Kovalskii A, Abdel-Hafiez M, Trainer DJ, Lechner EM, Iavarone M, Volkova O, Vasiliev A. Single crystal growth, transport and scanning tunneling microscopy and spectroscopy of FeSe1−xSx. CrystEngComm 2018. [DOI: 10.1039/c8ce00074c] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
“Ampoule in ampoule” design to grow single crystals of FeSe1−xSx.
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Affiliation(s)
- Dmitriy Chareev
- RAS
- Institute of Experimental Mineralogy
- Chernogolovka 123456
- Russia
- Ural Federal University
| | | | - Larisa Shvanskaya
- Lomonosov Moscow State University
- Moscow 119991
- Russia
- National University of Science and Technology “MISiS”
- Moscow 119049
| | - Andrey Kovalskii
- National University of Science and Technology “MISiS”
- Moscow 119049
- Russia
| | - Mahmoud Abdel-Hafiez
- National University of Science and Technology “MISiS”
- Moscow 119049
- Russia
- Goethe University Frankfurt
- Frankfurt am Main 60438
| | | | | | | | - Olga Volkova
- Ural Federal University
- Ekaterinburg 620002
- Russia
- Lomonosov Moscow State University
- Moscow 119991
| | - Alexander Vasiliev
- Lomonosov Moscow State University
- Moscow 119991
- Russia
- National University of Science and Technology “MISiS”
- Moscow 119049
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19
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Effect of nematic ordering on electronic structure of FeSe. Sci Rep 2016; 6:36834. [PMID: 27830747 PMCID: PMC5103297 DOI: 10.1038/srep36834] [Citation(s) in RCA: 71] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2016] [Accepted: 10/17/2016] [Indexed: 11/21/2022] Open
Abstract
Electronically driven nematic order is often considered as an essential ingredient of high-temperature superconductivity. Its elusive nature in iron-based superconductors resulted in a controversy not only as regards its origin but also as to the degree of its influence on the electronic structure even in the simplest representative material FeSe. Here we utilized angle-resolved photoemission spectroscopy and density functional theory calculations to study the influence of the nematic order on the electronic structure of FeSe and determine its exact energy and momentum scales. Our results strongly suggest that the nematicity in FeSe is electronically driven, we resolve the recent controversy and provide the necessary quantitative experimental basis for a successful theory of superconductivity in iron-based materials which takes into account both, spin-orbit interaction and electronic nematicity.
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