1
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Tazai R, Yamakawa Y, Kontani H. Charge-loop current order and Z 3 nematicity mediated by bond order fluctuations in kagome metals. Nat Commun 2023; 14:7845. [PMID: 38030600 PMCID: PMC10687221 DOI: 10.1038/s41467-023-42952-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2022] [Accepted: 10/25/2023] [Indexed: 12/01/2023] Open
Abstract
Recent experiments on geometrically frustrated kagome metal AV3Sb5 (A = K, Rb, Cs) have revealed the emergence of the charge loop current (cLC) order near the bond order (BO) phase. However, the origin of the cLC and its interplay with other phases have been uncovered. Here, we propose a novel mechanism of the cLC state, by focusing on the BO phase common in kagome metals. The BO fluctuations in kagome metals, which emerges due to the Coulomb interaction and the electron-phonon coupling, mediate the odd-parity particle-hole condensation that gives rise to the topological current order. Furthermore, the predicted cLC+BO phase gives rise to the Z3-nematic state in addition to the giant anomalous Hall effect. The present theory predicts the close relationship between the cLC, the BO, and the nematicity, which is significant to understand the cascade of quantum electron states in kagome metals. The present scenario provides a natural understanding.
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Grants
- JP20K22328 Ministry of Education, Culture, Sports, Science and Technology (MEXT)
- JP22K14003 Ministry of Education, Culture, Sports, Science and Technology (MEXT)
- JP19H05825 Ministry of Education, Culture, Sports, Science and Technology (MEXT)
- JP20K03858 Ministry of Education, Culture, Sports, Science and Technology (MEXT)
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Affiliation(s)
- Rina Tazai
- Yukawa Institute for Theoretical Physics, Kyoto University, Kyoto, 606-8502, Japan.
| | - Youichi Yamakawa
- Department of Physics, Nagoya University, Furo-cho, Nagoya, 464-8602, Japan
| | - Hiroshi Kontani
- Department of Physics, Nagoya University, Furo-cho, Nagoya, 464-8602, Japan
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2
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Tazai R, Yamakawa Y, Onari S, Kontani H. Mechanism of exotic density-wave and beyond-Migdal unconventional superconductivity in kagome metal AV 3Sb 5 (A = K, Rb, Cs). SCIENCE ADVANCES 2022; 8:eabl4108. [PMID: 35363527 PMCID: PMC10938589 DOI: 10.1126/sciadv.abl4108] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/13/2021] [Accepted: 02/09/2022] [Indexed: 05/12/2023]
Abstract
Exotic quantum phase transitions in metals, such as the electronic nematic state, have been discovered one after another and found to be universal now. The emergence of unconventional density-wave (DW) order in frustrated kagome metal AV3Sb5 and its interplay with exotic superconductivity attract increasing attention. We find that the DW in kagome metal is the bond order, because the sizable intersite attraction is caused by the quantum interference among paramagnons. This mechanism is important in kagome metals because the geometrical frustration prohibits the freezing of paramagnons. In addition, we uncover that moderate bond-order fluctuations mediate sizable pairing glue, and this mechanism gives rise to both singlet s-wave and triplet p-wave superconductivity. Furthermore, characteristic pressure-induced phase transitions in CsV3Cb5 are naturally understood by the present theory. Thus, both the exotic density wave and the superconductivity in geometrically frustrated kagome metals are explained by the quantum interference mechanism.
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3
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Onari S, Kontani H. SU(4) Valley+Spin Fluctuation Interference Mechanism for Nematic Order in Magic-Angle Twisted Bilayer Graphene: The Impact of Vertex Corrections. PHYSICAL REVIEW LETTERS 2022; 128:066401. [PMID: 35213199 DOI: 10.1103/physrevlett.128.066401] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/16/2020] [Revised: 08/10/2021] [Accepted: 01/07/2022] [Indexed: 06/14/2023]
Abstract
In the magic-angle twisted bilayer graphene (MATBG), one of the most remarkable observations is the C_{3}-symmetry-breaking nematic state. We identify that the nematicity in MATBG is the E-symmetry ferro bond order, which is the modulation of correlated hopping integrals owing to the E-symmetry particle-hole pairing condensation. The nematicity in MATBG originates from prominent quantum interference among SU(4) valley+spin composite fluctuations. This novel "valley+spin fluctuation interference mechanism" is revealed by the density wave equation analysis for the realistic multiorbital Hubbard model for MATBG. We find that the nematic state is robust once three van Hove singularity points exist in each valley. This interference mechanism also causes novel time-reversal-symmetry-broken valley polarization accompanied by a charge loop current. We discuss interesting similarities and differences between MATBG and Fe-based superconductors.
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Affiliation(s)
- Seiichiro Onari
- Department of Physics, Nagoya University, Furo-cho, Nagoya 464-8602, Japan
| | - Hiroshi Kontani
- Department of Physics, Nagoya University, Furo-cho, Nagoya 464-8602, Japan
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4
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Yamamoto Y, Yamaoka H, Uozumi T, Hariki A, Onari S, Yamaura JI, Ishii K, Kawai T, Yoshida M, Taguchi M, Kobayashi K, Lin JF, Hiraoka N, Ishii H, Tsuei KD, Okanishi H, Iimura S, Matsuishi S, Hosono H, Mizuki J. Electronic and crystal structures of LnFeAsO 1-xH x( Ln= La, Sm) studied by x-ray absorption spectroscopy, x-ray emission spectroscopy, and x-ray diffraction (part I: carrier-doping dependence). JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2021; 33:255602. [PMID: 33878750 DOI: 10.1088/1361-648x/abf9b9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2021] [Accepted: 04/20/2021] [Indexed: 06/12/2023]
Abstract
A carrier doping by a hydrogen substitution in LaFeAsO1-xHxis known to cause two superconducting (SC) domes with the magnetic order at both end sides of the doping. In contrast, SmFeAsO1-xHxhas a similar phase diagram but shows single SC dome. Here, we investigated the electronic and crystal structures for iron oxynitrideLnFeAsO1-xHx(Ln= La, Sm) with the range ofx= 0-0.5 by using x-ray absorption spectroscopy, x-ray emission spectroscopy, and x-ray diffraction. For both compounds, we observed that the pre-edge peaks of x-ray absorption spectra near the Fe-Kedge were reduced in intensity on doping. The character arises from the weaker As-Fe hybridization with the longer As-Fe distance in the higher doped region. We can reproduce the spectra near the Fe-Kedge according to the Anderson impurity model with realistic valence structures using the local-density approximation (LDA) plus dynamical mean-field theory (DMFT). ForLn= Sm, the integrated-absolute difference (IAD) analysis from x-ray Fe-Kβemission spectra increases significantly. This is attributed to the enhancement of magnetic moment of Fe 3delectrons stemming from the localized picture in the higher doped region. A theoretical simulation implementing the self-consistent vertex-correction method reveals that the single dome superconducting phase forLn= Sm arises from a better nesting condition in comparison withLn= La.
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Affiliation(s)
- Yoshiya Yamamoto
- Graduate School of Science and Technology, Kwansei Gakuin University, Sanda, Hyogo 669-1337, Japan
| | | | - Takayuki Uozumi
- Department of Physics and electronics, Osaka Prefecture University, 1-1 Gakuen, Nakaku, Sakai, Osaka 599-8531, Japan
| | - Atsushi Hariki
- Department of Physics and electronics, Osaka Prefecture University, 1-1 Gakuen, Nakaku, Sakai, Osaka 599-8531, Japan
| | - Seiichiro Onari
- Department of Physics, Nagoya University, Chikusa, Nagoya 464-8602, Japan
| | - Jun-Ichi Yamaura
- Materials Research Center for Element Strategy, Tokyo Institute of Technology, Yokohama, Kanagawa 226-8503, Japan
| | - Kenji Ishii
- Synchrotron Radiation Research Center, National Institutes for Quantum and Radiological Science and Technology, Hyogo 679-5148, Japan
| | - Takuma Kawai
- Graduate School of Science and Technology, Kwansei Gakuin University, Sanda, Hyogo 669-1337, Japan
| | - Masahiro Yoshida
- Graduate School of Science and Technology, Kwansei Gakuin University, Sanda, Hyogo 669-1337, Japan
| | - Munetaka Taguchi
- Toshiba Nanoanalysis Corporation, Kawasaki, Kanagawa 212-8583, Japan
| | - Kensuke Kobayashi
- Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki 305-0801, Japan
| | - Jung-Fu Lin
- Department of Geological Sciences, The University of Texas at Austin, Austin, Texas 78712, United States of America
| | - Nozomu Hiraoka
- National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan
| | - Hirofumi Ishii
- National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan
| | - Ku-Ding Tsuei
- National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan
| | - Hiroshi Okanishi
- Laboratory for Materials and Structures, Tokyo Institute of Technology, Yokohama 226-8503, Japan
| | - Soshi Iimura
- Laboratory for Materials and Structures, Tokyo Institute of Technology, Yokohama 226-8503, Japan
| | - Satoru Matsuishi
- Laboratory for Materials and Structures, Tokyo Institute of Technology, Yokohama 226-8503, Japan
| | - Hideo Hosono
- Materials Research Center for Element Strategy, Tokyo Institute of Technology, Yokohama, Kanagawa 226-8503, Japan
- Laboratory for Materials and Structures, Tokyo Institute of Technology, Yokohama 226-8503, Japan
| | - Jun'ichiro Mizuki
- Graduate School of Science and Technology, Kwansei Gakuin University, Sanda, Hyogo 669-1337, Japan
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5
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Huh SS, Kim YS, Kyung WS, Jung JK, Kappenberger R, Aswartham S, Büchner B, Ok JM, Kim JS, Dong C, Hu JP, Cho SH, Shen DW, Denlinger JD, Kim YK, Kim C. Momentum dependent [Formula: see text] band splitting in LaFeAsO. Sci Rep 2020; 10:19377. [PMID: 33168851 PMCID: PMC7652889 DOI: 10.1038/s41598-020-75600-w] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2020] [Accepted: 10/16/2020] [Indexed: 11/10/2022] Open
Abstract
The nematic phase in iron based superconductors (IBSs) has attracted attention with a notion that it may provide important clue to the superconductivity. A series of angle-resolved photoemission spectroscopy (ARPES) studies were performed to understand the origin of the nematic phase. However, there is lack of ARPES study on LaFeAsO nematic phase. Here, we report the results of ARPES studies of the nematic phase in LaFeAsO. Degeneracy breaking between the [Formula: see text] and [Formula: see text] hole bands near the [Formula: see text] and M point is observed in the nematic phase. Different temperature dependent band splitting behaviors are observed at the [Formula: see text] and M points. The energy of the band splitting near the M point decreases as the temperature decreases while it has little temperature dependence near the [Formula: see text] point. The nematic nature of the band shift near the M point is confirmed through a detwin experiment using a piezo device. Since a momentum dependent splitting behavior has been observed in other iron based superconductors, our observation confirms that the behavior is a universal one among iron based superconductors.
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Affiliation(s)
- S. S. Huh
- Center for Correlated Electron Systems, Institute for Basic Science (IBS), Seoul, 08826 Republic of Korea
- Department of Physics and Astronomy, Seoul National University (SNU), Seoul, 08826 Republic of Korea
| | - Y. S. Kim
- Center for Correlated Electron Systems, Institute for Basic Science (IBS), Seoul, 08826 Republic of Korea
- Department of Physics and Astronomy, Seoul National University (SNU), Seoul, 08826 Republic of Korea
| | - W. S. Kyung
- Center for Correlated Electron Systems, Institute for Basic Science (IBS), Seoul, 08826 Republic of Korea
- Department of Physics and Astronomy, Seoul National University (SNU), Seoul, 08826 Republic of Korea
| | - J. K. Jung
- Center for Correlated Electron Systems, Institute for Basic Science (IBS), Seoul, 08826 Republic of Korea
- Department of Physics and Astronomy, Seoul National University (SNU), Seoul, 08826 Republic of Korea
| | - R. Kappenberger
- Leibniz Institute for Solid State and Materials Research, IFW-Dresden, 01069 Dresden, Germany
| | - S. Aswartham
- Leibniz Institute for Solid State and Materials Research, IFW-Dresden, 01069 Dresden, Germany
| | - B. Büchner
- Leibniz Institute for Solid State and Materials Research, IFW-Dresden, 01069 Dresden, Germany
- Institute of Solid State Physics, TU Dresden, 01069 Dresden, Germany
| | - J. M. Ok
- Center for Artificial Low Dimensional Electronic Systems, Institute of Basic Science, Pohang, 790-784 Republic of Korea
- Department of Physics, Pohang University of Science and Technology, Pohang, 790-784 Republic of Korea
| | - J. S. Kim
- Center for Artificial Low Dimensional Electronic Systems, Institute of Basic Science, Pohang, 790-784 Republic of Korea
- Department of Physics, Pohang University of Science and Technology, Pohang, 790-784 Republic of Korea
| | - C. Dong
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190 People’s Republic of China
- Collaborative Innovation Center of Quantum Matter, Beijing, People’s Republic of China
| | - J. P. Hu
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190 People’s Republic of China
- Collaborative Innovation Center of Quantum Matter, Beijing, People’s Republic of China
| | - S. H. Cho
- State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology (SIMIT), Chinese Academy of Sciences, Shanghai, 200050 People’s Republic of China
| | - D. W. Shen
- State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology (SIMIT), Chinese Academy of Sciences, Shanghai, 200050 People’s Republic of China
| | - J. D. Denlinger
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 USA
| | - Y. K. Kim
- Department of Physics, Korea Advanced Institute of Science and Technology, Daejeon, 34141 Republic of Korea
- Graduate School of Nanoscience and Technology, Korea Advanced Institute of Science and Technology, Daejeon, 34141 Republic of Korea
| | - C. Kim
- Center for Correlated Electron Systems, Institute for Basic Science (IBS), Seoul, 08826 Republic of Korea
- Department of Physics and Astronomy, Seoul National University (SNU), Seoul, 08826 Republic of Korea
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6
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Udina M, Grilli M, Benfatto L, Chubukov AV. Raman Response in the Nematic Phase of FeSe. PHYSICAL REVIEW LETTERS 2020; 124:197602. [PMID: 32469539 DOI: 10.1103/physrevlett.124.197602] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/29/2019] [Revised: 01/21/2020] [Accepted: 04/21/2020] [Indexed: 06/11/2023]
Abstract
Raman experiments on bulk FeSe revealed that the low-frequency part of the B_{1g} Raman response R_{B1g}(Ω), which probes nematic fluctuations, rapidly decreases below the nematic transition at T_{n}∼85 K. Such behavior is expected when a gap opens up and at a first glance is inconsistent with the fact that FeSe remains a metal below T_{n}. We argue that the drop of R_{B1g}(Ω) can be ascribed to the fact that the nematic order drastically changes the orbital content of low-energy excitations near hole and electron pockets, making them nearly mono-orbital. In this situation, the B_{1g} Raman response gets reduced by the same vertex corrections that enforce charge conservation in the symmetric Raman channel. The reduction holds at low frequencies and gives rise to gaplike behavior of R_{B1g}(Ω). We also show that the enhancement of the B_{1g} Raman response near T_{n} is consistent with the sign change of the nematic order parameter between hole and electron pockets.
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Affiliation(s)
- Mattia Udina
- Department of Physics and ISC-CNR, "Sapienza" University of Rome, P.le A. Moro 5, 00185 Rome, Italy
| | - Marco Grilli
- Department of Physics and ISC-CNR, "Sapienza" University of Rome, P.le A. Moro 5, 00185 Rome, Italy
| | - Lara Benfatto
- Department of Physics and ISC-CNR, "Sapienza" University of Rome, P.le A. Moro 5, 00185 Rome, Italy
| | - Andrey V Chubukov
- School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota 55455, USA
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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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Gati E, Böhmer AE, Bud'ko SL, Canfield PC. Bulk Superconductivity and Role of Fluctuations in the Iron-Based Superconductor FeSe at High Pressures. PHYSICAL REVIEW LETTERS 2019; 123:167002. [PMID: 31702365 DOI: 10.1103/physrevlett.123.167002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/04/2019] [Indexed: 06/10/2023]
Abstract
The iron-based superconductor FeSe offers a unique possibility to study the interplay of superconductivity with purely nematic as well magnetic-nematic order by pressure (p) tuning. By measuring specific heat under p up to 2.36 GPa, we study the multiple phases in FeSe using a thermodynamic probe. We conclude that superconductivity is bulk across the entire p range and competes with magnetism. In addition, whenever magnetism is present, fluctuations exist over a wide temperature range above both the bulk superconducting and the magnetic transitions. Whereas the magnetic fluctuations are likely temporal, the superconducting fluctuations may be either temporal or spatial. These observations highlight similarities between FeSe and underdoped cuprate superconductors.
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Affiliation(s)
- Elena Gati
- Ames Laboratory, U.S. Department of Energy, Iowa State University, Ames, Iowa 50011, USA
- Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA
| | - Anna E Böhmer
- Ames Laboratory, U.S. Department of Energy, Iowa State University, Ames, Iowa 50011, USA
- Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA
| | - Sergey L Bud'ko
- Ames Laboratory, U.S. Department of Energy, Iowa State University, Ames, Iowa 50011, USA
- Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA
| | - Paul C Canfield
- Ames Laboratory, U.S. Department of Energy, Iowa State University, Ames, Iowa 50011, USA
- Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA
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9
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Pfau H, Chen SD, Yi M, Hashimoto M, Rotundu CR, Palmstrom JC, Chen T, Dai PC, Straquadine J, Hristov A, Birgeneau RJ, Fisher IR, Lu D, Shen ZX. Momentum Dependence of the Nematic Order Parameter in Iron-Based Superconductors. PHYSICAL REVIEW LETTERS 2019; 123:066402. [PMID: 31491189 DOI: 10.1103/physrevlett.123.066402] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2019] [Indexed: 06/10/2023]
Abstract
The momentum dependence of the nematic order parameter is an important ingredient in the microscopic description of iron-based high-temperature superconductors. While recent reports on FeSe indicate that the nematic order parameter changes sign between electron and hole bands, detailed knowledge is still missing for other compounds. Combining angle-resolved photoemission spectroscopy with uniaxial strain tuning, we measure the nematic band splitting in both FeSe and BaFe_{2}As_{2} without interference from either twinning or magnetic order. We find that the nematic order parameter exhibits the same momentum dependence in both compounds with a sign change between the Brillouin center and the corner. This suggests that the same microscopic mechanism drives the nematic order in spite of the very different phase diagrams.
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Affiliation(s)
- H Pfau
- Stanford Institute of Materials and Energy Sience, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
- Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - S D Chen
- Geballe Laboratory for Advanced Materials, Department of Applied Physics, Stanford University, Stanford, 94305 California, USA
| | - M Yi
- Department of Physics, University of California, Berkeley, 94720 California, USA
- Department of Physics and Astronomy, Rice University, Houston, 77005 Texas, USA
| | - M Hashimoto
- Stanford Synchrotron Radiation Lightsource, SLAC National Acelerator Laboratory, Menlo Park, 94025 California, USA
| | - C R Rotundu
- Stanford Institute of Materials and Energy Sience, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
| | - J C Palmstrom
- Stanford Institute of Materials and Energy Sience, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
- Geballe Laboratory for Advanced Materials, Department of Applied Physics, Stanford University, Stanford, 94305 California, USA
| | - T Chen
- Department of Physics and Astronomy, Rice University, Houston, 77005 Texas, USA
| | - P-C Dai
- Department of Physics and Astronomy, Rice University, Houston, 77005 Texas, USA
| | - J Straquadine
- Geballe Laboratory for Advanced Materials, Department of Applied Physics, Stanford University, Stanford, 94305 California, USA
| | - A Hristov
- Geballe Laboratory for Advanced Materials, Department of Applied Physics, Stanford University, Stanford, 94305 California, USA
| | - R J Birgeneau
- Department of Physics, University of California, Berkeley, 94720 California, USA
| | - I R Fisher
- Stanford Institute of Materials and Energy Sience, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
- Geballe Laboratory for Advanced Materials, Department of Applied Physics, Stanford University, Stanford, 94305 California, USA
| | - D Lu
- Stanford Synchrotron Radiation Lightsource, SLAC National Acelerator Laboratory, Menlo Park, 94025 California, USA
| | - Z-X Shen
- Stanford Institute of Materials and Energy Sience, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
- Geballe Laboratory for Advanced Materials, Department of Applied Physics, Stanford University, Stanford, 94305 California, USA
- Department of Physics, Stanford University, Stanford, 94305 California, USA
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10
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Chen T, Chen Y, Kreisel A, Lu X, Schneidewind A, Qiu Y, Park JT, Perring TG, Stewart JR, Cao H, Zhang R, Li Y, Rong Y, Wei Y, Andersen BM, Hirschfeld PJ, Broholm C, Dai P. Anisotropic spin fluctuations in detwinned FeSe. NATURE MATERIALS 2019; 18:709-716. [PMID: 31110345 PMCID: PMC7895486 DOI: 10.1038/s41563-019-0369-5] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/04/2018] [Accepted: 04/10/2019] [Indexed: 05/05/2023]
Abstract
Superconductivity in FeSe emerges from a nematic phase that breaks four-fold rotational symmetry in the iron plane. This phase may arise from orbital ordering, spin fluctuations or hidden magnetic quadrupolar order. Here we use inelastic neutron scattering on a mosaic of single crystals of FeSe, detwinned by mounting on a BaFe2As2 substrate to demonstrate that spin excitations are most intense at the antiferromagnetic wave vectors QAF = (±1, 0) at low energies E = 6-11 meV in the normal state. This two-fold (C2) anisotropy is reduced at lower energies, 3-5 meV, indicating a gapped four-fold (C4) mode. In the superconducting state, however, the strong nematic anisotropy is again reflected in the spin resonance (E = 3.6 meV) at QAF with incommensurate scattering around 5-6 meV. Our results highlight the extreme electronic anisotropy of the nematic phase of FeSe and are consistent with a highly anisotropic superconducting gap driven by spin fluctuations.
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Affiliation(s)
- Tong Chen
- Department of Physics and Astronomy, Rice University, Houston, TX, USA
| | - Youzhe Chen
- Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD, USA
| | - Andreas Kreisel
- Institut für Theoretische Physik, Universität Leipzig, Leipzig, Germany
| | - Xingye Lu
- Center for Advanced Quantum Studies and Department of Physics, Beijing Normal University, Beijing, China.
| | - Astrid Schneidewind
- Forschungszentrum Jülich GmbH, Jülich Center for Neutron Sciences at MLZ, Garching, Germany
| | - Yiming Qiu
- NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, MD, USA
| | - J T Park
- Heinz Maier-Leibnitz Zentrum (MLZ), Technische Universität München, Garching, Germany
| | - Toby G Perring
- ISIS Facility, STFC Rutherford-Appleton Laboratory, Didcot, UK
| | - J Ross Stewart
- ISIS Facility, STFC Rutherford-Appleton Laboratory, Didcot, UK
| | - Huibo Cao
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA
| | - Rui Zhang
- Department of Physics and Astronomy, Rice University, Houston, TX, USA
| | - Yu Li
- Department of Physics and Astronomy, Rice University, Houston, TX, USA
| | - Yan Rong
- Center for Advanced Quantum Studies and Department of Physics, Beijing Normal University, Beijing, China
| | - Yuan Wei
- Institute of Physics, Chinese Academy of Sciences, Beijing, China
| | - Brian M Andersen
- Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark
| | - P J Hirschfeld
- Department of Physics, University of Florida, Gainesville, FL, USA
| | - Collin Broholm
- Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD, USA
- NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, MD, USA
| | - Pengcheng Dai
- Department of Physics and Astronomy, Rice University, Houston, TX, USA.
- Center for Advanced Quantum Studies and Department of Physics, Beijing Normal University, Beijing, China.
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11
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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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12
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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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13
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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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