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Li P, Liao S, Wang Z, Li H, Su S, Zhang J, Chen Z, Jiang Z, Liu Z, Yang L, Huai L, He J, Cui S, Sun Z, Yan Y, Cao G, Shen D, Jiang J, Feng D. Evidence of electron interaction with an unidentified bosonic mode in superconductor CsCa 2Fe 4As 4F 2. Nat Commun 2024; 15:6433. [PMID: 39085266 PMCID: PMC11291980 DOI: 10.1038/s41467-024-50833-9] [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: 02/01/2024] [Accepted: 07/22/2024] [Indexed: 08/02/2024] Open
Abstract
The kink structure in band dispersion usually refers to a certain electron-boson interaction, which is crucial in understanding the pairing in unconventional superconductors. Here we report the evidence of the observation of a kink structure in Fe-based superconductor CsCa2Fe4As4F2 using angle-resolved photoemission spectroscopy. The kink shows an orbital selective and momentum dependent behavior, which is located at 15 meV below Fermi level along the Γ - M direction at the band with dxz orbital character and vanishes when approaching the Γ - X direction, correlated with a slight decrease of the superconducting gap. Most importantly, this kink structure disappears when the superconducting gap closes, indicating that the corresponding bosonic mode (~ 9 ± 1 meV) is closely related to superconductivity. However, the origin of this mode remains unidentified, since it cannot be related to phonons or the spin resonance mode (~15 meV) observed by inelastic neutron scattering. The behavior of this mode is rather unique and challenges our present understanding of the superconducting paring mechanism of the bilayer FeAs-based superconductors.
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Affiliation(s)
- Peng Li
- Shool of Emerging Technology, University of Science and Technology of China, Hefei, 230026, China
| | - Sen Liao
- Shool of Emerging Technology, University of Science and Technology of China, Hefei, 230026, China
| | - Zhicheng Wang
- Key Laboratory of Quantum Materials and Devices of Ministry of Education, School of Physics, Southeast University, Nanjing, 211189, China
| | - Huaxun Li
- School of Physics, Zhejiang University, Hangzhou, 310058, China
| | - Shiwu Su
- Shool of Emerging Technology, University of Science and Technology of China, Hefei, 230026, China
| | - Jiakang Zhang
- Shool of Emerging Technology, University of Science and Technology of China, Hefei, 230026, China
| | - Ziyuan Chen
- Shool of Emerging Technology, University of Science and Technology of China, Hefei, 230026, China
| | - Zhicheng Jiang
- National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, 230026, China
- School of Nuclear Science and Technology, University of Science and Technology of China, Hefei, 230026, China
| | - Zhengtai Liu
- Shanghai Synchrotron Radiation Facility, Shanghai Advanced Research Institute, Chinese Academy of Sciences, Shanghai, 201210, China
| | - Lexian Yang
- State Key Laboratory of Low Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing, 100084, China
| | - Linwei Huai
- CAS Key Laboratory of Strongly-coupled Quantum Matter Physics, University of Science and Technology of China, Hefei, Anhui, 230026, China
| | - Junfeng He
- CAS Key Laboratory of Strongly-coupled Quantum Matter Physics, University of Science and Technology of China, Hefei, Anhui, 230026, China
| | - Shengtao Cui
- National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, 230026, China
| | - Zhe Sun
- National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, 230026, China
| | - Yajun Yan
- Shool of Emerging Technology, University of Science and Technology of China, Hefei, 230026, China
| | - Guanghan Cao
- School of Physics, Zhejiang University, Hangzhou, 310058, China
| | - Dawei Shen
- National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, 230026, China
- School of Nuclear Science and Technology, University of Science and Technology of China, Hefei, 230026, China
| | - Juan Jiang
- Shool of Emerging Technology, University of Science and Technology of China, Hefei, 230026, China.
| | - Donglai Feng
- Shool of Emerging Technology, University of Science and Technology of China, Hefei, 230026, China.
- National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, 230026, China.
- School of Nuclear Science and Technology, University of Science and Technology of China, Hefei, 230026, China.
- New Cornerstone Science Laboratory, University of Science and Technology of China, Hefei, 230026, China.
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2
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Xie T, Liu C, Kajimoto R, Ikeuchi K, Li S, Luo H. Spin fluctuations in the 112-type iron-based superconductor Ca 0.82La 0.18Fe 0.96Ni 0.04As 2. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2022; 34:474001. [PMID: 36137515 DOI: 10.1088/1361-648x/ac9441] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/28/2022] [Accepted: 09/22/2022] [Indexed: 06/16/2023]
Abstract
We report time-of-flight inelastic neutron scattering (INS) investigations on the spin fluctuation spectrum in the 112-type iron-based superconductor (FeSC) Ca0.82La0.18Fe0.96Ni0.04As2(CaLa-112). In comparison to the 122-type FeSCs with a centrosymmetric tetragonal lattice structure (space groupI4/mmm) at room temperature and an in-plane stripe-type antiferromagnetic (AF) order at low temperature, the 112 system has a noncentrosymmetric structure (space groupP21) with additional zigzag arsenic chains between Ca/La layers and a magnetic ground state with similar wavevectorQAFbut different orientations of ordered moments in the parent compounds. Our INS study clearly reveals that the in-plane dispersions and the bandwidth of spin excitations in the superconducting CaLa-112 closely resemble to those in 122 systems. While the total fluctuating moments⟨m2⟩≈4.6±0.2μB2/Fe are larger than 122 system, the dynamic correlation lengths are similar (ξ ≈ 10 Å). These results suggest that superconductivity in iron arsenides may have a common magnetic origin under similar magnetic exchange couplings with a dual nature from local moments and itinerant electrons, despite their different magnetic patterns and lattice symmetries.
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Affiliation(s)
- Tao Xie
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190, People's Republic of China
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, United States of America
| | - Chang Liu
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190, People's Republic of China
| | - 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, People's Republic of China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190, People's Republic of China
- Songshan Lake Materials Laboratory, Dongguan, Guangdong 523808, People's Republic of China
| | - Huiqian Luo
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
- Songshan Lake Materials Laboratory, Dongguan, Guangdong 523808, People's Republic of China
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3
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Shen S, Zhang X, Wo H, Shen Y, Feng Y, Schneidewind A, Čermák P, Wang W, Zhao J. Neutron Spin Resonance in the Heavily Hole-Doped KFe_{2}As_{2} Superconductor. PHYSICAL REVIEW LETTERS 2020; 124:017001. [PMID: 31976731 DOI: 10.1103/physrevlett.124.017001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/15/2019] [Indexed: 06/10/2023]
Abstract
We report high-resolution neutron scattering measurements of the low energy spin fluctuations of KFe_{2}As_{2}, the end member of the hole-doped Ba_{1-x}K_{x}Fe_{2}As_{2} family with only hole pockets, above and below its superconducting transition temperature T_{c} (∼3.5 K). Our data reveal clear spin fluctuations at the incommensurate wave vector (0.5±δ, 0, L), (δ=0.2) (1-Fe unit cell), which exhibit L-modulation peaking at L=0.5. Upon cooling to the superconducting state, the incommensurate spin fluctuations gradually open a spin gap and form a sharp spin resonance mode. The incommensurability (2δ=0.4) of the resonance mode (∼1.2 meV) is considerably larger than the previously reported value (2δ≈0.32) at higher energies (≥∼6 meV). The determination of the momentum structure of spin fluctuation in the low energy limit allows a direct comparison with the realistic Fermi surface and superconducting gap structure. Our results point to an s-wave pairing with a reversed sign between the hole pockets near the zone center in KFe_{2}As_{2}.
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Affiliation(s)
- Shoudong Shen
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China
| | - Xiaowen Zhang
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China
| | - Hongliang Wo
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China
| | - Yao Shen
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China
| | - Yu Feng
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China
| | - A Schneidewind
- Jülich Centre for Neutron Science (JCNS) at Heinz Maier-Leibnitz Zentrum (MLZ), Forschungszentrum Jülich GmbH, Lichtenbergstr. 1, 85748 Garching, Germany
| | - P Čermák
- Jülich Centre for Neutron Science (JCNS) at Heinz Maier-Leibnitz Zentrum (MLZ), Forschungszentrum Jülich GmbH, Lichtenbergstr. 1, 85748 Garching, Germany
| | - Wenbin Wang
- Institute of Nanoelectronic Devices and Quantum Computing, Fudan University, Shanghai 200433, China
| | - Jun Zhao
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing, 210093, China
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4
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Li Y, Yin Z, Liu Z, Wang W, Xu Z, Song Y, Tian L, Huang Y, Shen D, Abernathy DL, Niedziela JL, Ewings RA, Perring TG, Pajerowski DM, Matsuda M, Bourges P, Mechthild E, Su Y, Dai P. Coexistence of Ferromagnetic and Stripe Antiferromagnetic Spin Fluctuations in SrCo_{2}As_{2}. PHYSICAL REVIEW LETTERS 2019; 122:117204. [PMID: 30951336 DOI: 10.1103/physrevlett.122.117204] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/08/2018] [Indexed: 06/09/2023]
Abstract
We use inelastic neutron scattering to study energy and wave vector dependence of spin fluctuations in SrCo_{2}As_{2}, derived from SrFe_{2-x}Co_{x}As_{2} iron pnictide superconductors. Our data reveal the coexistence of antiferromagnetic (AF) and ferromagnetic (FM) spin fluctuations at wave vectors Q_{AF}=(1,0) and Q_{FM}=(0,0)/(2,0), respectively. By comparing neutron scattering results with those of dynamic mean field theory calculation and angle-resolved photoemission spectroscopy experiments, we conclude that both AF and FM spin fluctuations in SrCo_{2}As_{2} are closely associated with a flatband of the e_{g} orbitals near the Fermi level, different from the t_{2g} orbitals in superconducting SrFe_{2-x}Co_{x}As_{2}. Therefore, Co substitution in SrFe_{2-x}Co_{x}As_{2} induces a t_{2g} to e_{g} orbital switching, and is responsible for FM spin fluctuations detrimental to the singlet pairing superconductivity.
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Affiliation(s)
- Yu Li
- Department of Physics and Astronomy, Rice University, Houston, Texas 77005, USA
- Department of Physics, Beijing Normal University, Beijing 100875, China
| | - Zhiping Yin
- Department of Physics, Beijing Normal University, Beijing 100875, China
| | - Zhonghao Liu
- State Key Laboratory of Functional Materials for Informatics and Center for Excellence in Superconducting Electronics, SIMIT, Chinese Academy of Sciences, Shanghai 200050, China
| | - Weiyi Wang
- Department of Physics and Astronomy, Rice University, Houston, Texas 77005, USA
| | - Zhuang Xu
- Department of Physics, Beijing Normal University, Beijing 100875, China
| | - Yu Song
- Department of Physics and Astronomy, Rice University, Houston, Texas 77005, USA
| | - Long Tian
- Department of Physics, Beijing Normal University, Beijing 100875, China
| | - Yaobo Huang
- Shanghai Synchrotron Radiation Facility, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201204, China
| | - Dawei Shen
- State Key Laboratory of Functional Materials for Informatics and Center for Excellence in Superconducting Electronics, SIMIT, Chinese Academy of Sciences, Shanghai 200050, China
| | - D L Abernathy
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - J L Niedziela
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - R A Ewings
- ISIS Pulsed Neutron and Muon Source, STFC Rutherford Appleton Laboratory, Didcot, Oxfordshire, OX11 0QX, United Kingdom
| | - T G Perring
- ISIS Pulsed Neutron and Muon Source, STFC Rutherford Appleton Laboratory, Didcot, Oxfordshire, OX11 0QX, United Kingdom
| | - Daniel M Pajerowski
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - Masaaki Matsuda
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - Philippe Bourges
- Laboratoire Léon Brillouin, CEA-CNRS, Université Paris-Saclay, CEA Saclay, 91191 Gif-sur-Yvette, France
| | - Enderle Mechthild
- Institut Laue-Langevin, 6 rue Jules Horowitz, Boîte Postale 156, 38042 Grenoble Cedex 9, France
| | - Yixi Su
- Jülich Centre for Neutron Science (JCNS) at Heinz Maier-Leibnitz Zentrum (MLZ), Forschungszentrum Jülich, Lichtenbergstrasse 1, 85747 Garching, Germany
| | - Pengcheng Dai
- Department of Physics and Astronomy, Rice University, Houston, Texas 77005, USA
- Department of Physics, Beijing Normal University, Beijing 100875, China
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5
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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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6
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Xie T, Gong D, Ghosh H, Ghosh A, Soda M, Masuda T, Itoh S, Bourdarot F, Regnault LP, Danilkin S, Li S, Luo H. Neutron Spin Resonance in the 112-Type Iron-Based Superconductor. PHYSICAL REVIEW LETTERS 2018; 120:137001. [PMID: 29694229 DOI: 10.1103/physrevlett.120.137001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/08/2017] [Indexed: 06/08/2023]
Abstract
We use inelastic neutron scattering to study the low-energy spin excitations of the 112-type iron pnictide Ca_{0.82}La_{0.18}Fe_{0.96}Ni_{0.04}As_{2} with bulk superconductivity below T_{c}=22 K. A two-dimensional spin resonance mode is found around E=11 meV, where the resonance energy is almost temperature independent and linearly scales with T_{c} along with other iron-based superconductors. Polarized neutron analysis reveals the resonance is nearly isotropic in spin space without any L modulations. Because of the unique monoclinic structure with additional zigzag arsenic chains, the As 4p orbitals contribute to a three-dimensional hole pocket around the Γ point and an extra electron pocket at the X point. Our results suggest that the energy and momentum distribution of the spin resonance does not directly respond to the k_{z} dependence of the fermiology, and the spin resonance intrinsically is a spin-1 mode from singlet-triplet excitations of the Cooper pairs in the case of weak spin-orbital coupling.
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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
| | - 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
| | - Haranath Ghosh
- Homi Bhabha National Institute, Anushakti Nagar, Mumbai 400094, India
- Human Resources development section, Raja Ramanna Centre for Advanced Technology, Indore 452013, India
| | - Abyay Ghosh
- Homi Bhabha National Institute, Anushakti Nagar, Mumbai 400094, India
- Human Resources development section, Raja Ramanna Centre for Advanced Technology, Indore 452013, India
| | - Minoru Soda
- The Institute for Solid State Physics, The University of Tokyo, Chiba 277-8581, Japan
| | - Takatsugu Masuda
- The Institute for Solid State Physics, The University of Tokyo, Chiba 277-8581, Japan
| | - Shinichi Itoh
- Institute of Materials Structure Science, High Energy Accelerator Research Organization, Tsukuba, Ibaraki 305-0801, Japan
| | | | - Louis-Pierre Regnault
- Intitut Laue Langevin, 71 avenue des Martyrs, CS 20156, 38042 Grenoble Cedex, France
| | - Sergey Danilkin
- Australian Centre for Neutron Scattering, Australian Nuclear Science and Technology Organization, Lucas Heights, New South Wales 2234, Australia
| | - 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
| | - Huiqian Luo
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
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7
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Magnetic moment evolution and spin freezing in doped BaFe 2As 2. Sci Rep 2017; 7:8003. [PMID: 28808249 PMCID: PMC5556117 DOI: 10.1038/s41598-017-07286-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2016] [Accepted: 06/27/2017] [Indexed: 12/02/2022] Open
Abstract
Fe-Kβ X-ray emission spectroscopy measurements reveal an asymmetric doping dependence of the magnetic moments μbare in electron- and hole-doped BaFe2As2. At low temperature, μbare is nearly constant in hole-doped samples, whereas it decreases upon electron doping. Increasing temperature substantially enhances μbare in the hole-doped region, which is naturally explained by the theoretically predicted crossover into a spin-frozen state. Our measurements demonstrate the importance of Hund’s-coupling and electronic correlations, especially for hole-doped BaFe2As2, and the inadequacy of a fully localized or fully itinerant description of the 122 family of Fe pnictides.
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8
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Yu R, Nevidomskyy AH. Competing superconducting channels in iron pnictides from the strong coupling theory with biquadratic spin interactions. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2016; 28:495702. [PMID: 27736803 DOI: 10.1088/0953-8984/28/49/495702] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
We study the symmetry and strength of the superconducting pairing in a two-orbital [Formula: see text] model for iron pnictides using the slave boson strong coupling approach. We show that the nearest-neighbor biquadratic interaction [Formula: see text] strongly affects the superconducting pairing phase diagram by promoting the [Formula: see text] B 1g and the [Formula: see text] A 1g channels. The resulting phase diagram consists of several competing pairing channels, including the isotropic [Formula: see text] A 1g channel, an anisotropic [Formula: see text] B 1g channel, and two [Formula: see text] pairing channels. We have investigated the evolution of superconducting states with electron doping, and find that the biquadratic interaction plays a crucial role in stabilizing the [Formula: see text] and even pure d-wave pairing in the heavily electron- and hole-doped regimes. In addition, we identify a novel orbital-B 1g pairing channel, which has a s-wave form factor but a B 1g symmetry. This channel has a comparable pairing amplitude to the d-wave pairing, and may strongly influence the superconducting gap anisotropy of the system in the overdoped regime. These findings are crucial in understanding the doping evolution of the superconducting gap anisotropy observed by angle resolved photoemission spectroscopy in the iron pnictides and iron chalcogenides, including the heavily K-doped BaFe2As2 and K-doped FeSe films.
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Affiliation(s)
- Rong Yu
- Department of Physics and Beijing Key Laboratory of Opto-electronic Functional Materials & Micro-nano Devices, Renmin University of China, Beijing 100872, People's Republic of China. Department of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China and Collaborative Innovation Center of Advanced Microstructures, Nanjing 210093, People's Republic of China
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9
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Suppression of spin-exciton state in hole overdoped iron-based superconductors. Sci Rep 2016; 6:23424. [PMID: 27005481 PMCID: PMC4804212 DOI: 10.1038/srep23424] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2015] [Accepted: 03/03/2016] [Indexed: 12/04/2022] Open
Abstract
The mechanism of Cooper pair formation in iron-based superconductors remains a controversial topic. The main question is whether spin or orbital fluctuations are responsible for the pairing mechanism. To solve this problem, a crucial clue can be obtained by examining the remarkable enhancement of magnetic neutron scattering signals appearing in a superconducting phase. The enhancement is called spin resonance for a spin fluctuation model, in which their energy is restricted below twice the superconducting gap value (2Δs), whereas larger energies are possible in other models such as an orbital fluctuation model. Here we report the doping dependence of low-energy magnetic excitation spectra in Ba1−xKxFe2As2 for 0.5 < x < 0.84 studied by inelastic neutron scattering. We find that the behavior of the spin resonance dramatically changes from optimum to overdoped regions. Strong resonance peaks are observed clearly below 2Δs in the optimum doping region, while they are absent in the overdoped region. Instead, there is a transfer of spectral weight from energies below 2Δs to higher energies, peaking at values of 3Δs for x = 0.84. These results suggest a reduced impact of magnetism on Cooper pair formation in the overdoped region.
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10
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Chen X, Dai P, Feng D, Xiang T, Zhang FC. Iron-based high transition temperature superconductors. Natl Sci Rev 2014. [DOI: 10.1093/nsr/nwu007] [Citation(s) in RCA: 148] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Abstract
In a superconductor electrons form pairs and electric transport becomes dissipation-less at low temperatures. Recently discovered iron-based superconductors have the highest superconducting transition temperature next to copper oxides. In this article, we review material aspects and physical properties of iron-based superconductors. We discuss the dependence of transition temperature on the crystal structure, the interplay between antiferromagnetism and superconductivity by examining neutron scattering experiments, and the electronic properties of these compounds obtained by angle-resolved photoemission spectroscopy in link with some results from scanning tunneling microscopy/spectroscopy measurements. Possible microscopic model for this class of compounds is discussed from a strong coupling point of view.
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Affiliation(s)
- Xianhui Chen
- Department of Physics, University of Science and Technology of China, Hefei, 230026, China
| | - Pengcheng Dai
- Department of Physics and Astronomy, Rice University, Houston, TX 77005, USA
- Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Donglai Feng
- Department of Physics, Fudan University, Shanghai 200433, China
| | - Tao Xiang
- Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- Collaborative Innovation Center of Quantum Matter, Beijing 100190, China
| | - Fu-Chun Zhang
- Department of Physics, Zhejiang University, Hangzhou, 310027, China
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11
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Liu B. Nonmagnetic impurity resonance states as a test of superconducting pairing symmetry in CeCoIn 5. PHYSICAL REVIEW B 2013; 88:245127. [DOI: 10.1103/physrevb.88.245127] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/01/2023]
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12
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Zhang C, Yu R, Su Y, Song Y, Wang M, Tan G, Egami T, Fernandez-Baca JA, Faulhaber E, Si Q, Dai P. Measurement of a double neutron-spin resonance and an anisotropic energy gap for underdoped superconducting NaFe0.985Co0.015As using inelastic neutron scattering. PHYSICAL REVIEW LETTERS 2013; 111:207002. [PMID: 24289703 DOI: 10.1103/physrevlett.111.207002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/22/2013] [Indexed: 06/02/2023]
Abstract
We use inelastic neutron scattering to show that superconductivity in electron-underdoped NaFe0.985Co0.015As induces a dispersive sharp resonance near E(r1)=3.25 meV and a broad dispersionless mode at E(r2)=6 meV. However, similar measurements on overdoped superconducting NaFe0.935Co0.045As find only a single sharp resonance at E(r)=7 meV. We connect these results with the observations of angle-resolved photoemission spectroscopy that the superconducting gaps in the electron Fermi pockets are anisotropic in the underdoped material but become isotropic in the overdoped case. Our analysis indicates that both the double neutron spin resonances and gap anisotropy originate from the orbital dependence of the superconducting pairing in the iron pnictides. Our discovery also shows the importance of the inelastic neutron scattering in detecting the multiorbital superconducting gap structures of iron pnictides.
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Affiliation(s)
- Chenglin Zhang
- Department of Physics and Astronomy, Rice University, Houston, Texas 77005, USA and Department of Physics and Astronomy, The University of Tennessee, Knoxville, Tennessee 37996-1200, USA
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13
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Lee CH, Steffens P, Qureshi N, Nakajima M, Kihou K, Iyo A, Eisaki H, Braden M. Universality of the dispersive spin-resonance mode in superconducting BaFe2As2. PHYSICAL REVIEW LETTERS 2013; 111:167002. [PMID: 24182293 DOI: 10.1103/physrevlett.111.167002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/19/2013] [Revised: 09/09/2013] [Indexed: 06/02/2023]
Abstract
Spin fluctuations in superconducting BaFe2(As(1-x)P(x))2 (x=0.34, T(c)=29.5 K) are studied using inelastic neutron scattering. Well-defined commensurate magnetic signals are observed at (π, 0), which is consistent with the nesting vector of the Fermi surface. Antiferromagnetic (AFM) spin fluctuations in the normal state exhibit a three-dimensional character reminiscent of the AFM order in nondoped BaFe2As2. A clear spin gap is observed in the superconducting phase forming a peak whose energy is significantly dispersed along the c axis. The bandwidth of dispersion becomes larger with approaching the AFM ordered phase universally in all superconducting BaFe2As2, indicating that the dispersive feature is attributed to three-dimensional AFM correlations. The results suggest a strong relationship between the magnetism and superconductivity.
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Affiliation(s)
- C H Lee
- National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki 305-8568, Japan and Transformative Research-Project on Iron Pnictides (TRIP), JST, Chiyoda, Tokyo 102-0075, Japan
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14
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Jayasekara W, Lee Y, Pandey A, Tucker GS, Sapkota A, Lamsal J, Calder S, Abernathy DL, Niedziela JL, Harmon BN, Kreyssig A, Vaknin D, Johnston DC, Goldman AI, McQueeney RJ. Stripe antiferromagnetic spin fluctuations in SrCo2As2. PHYSICAL REVIEW LETTERS 2013; 111:157001. [PMID: 24160618 DOI: 10.1103/physrevlett.111.157001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/16/2013] [Indexed: 06/02/2023]
Abstract
Inelastic neutron scattering measurements of paramagnetic SrCo2As2 at T=5 K reveal antiferromagnetic (AFM) spin fluctuations that are peaked at a wave vector of Q(AFM)=(1/2,1/2,1) and possess a large energy scale. These stripe spin fluctuations are similar to those found in AFe2As2 compounds, where spin-density wave AFM is driven by Fermi surface nesting between electron and hole pockets separated by Q(AFM). SrCo2As2 has a more complex Fermi surface and band-structure calculations indicate a potential instability toward either a ferromagnetic or stripe AFM ground state. The results suggest that stripe AFM magnetism is a general feature of both iron and cobalt-based arsenides and the search for spin fluctuation-induced unconventional superconductivity should be expanded to include cobalt-based compounds.
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Affiliation(s)
- W Jayasekara
- Ames Laboratory, Ames, Iowa 50011, USA and Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA
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15
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Blomberg EC, Tanatar MA, Fernandes RM, Mazin II, Shen B, Wen HH, Johannes MD, Schmalian J, Prozorov R. Sign-reversal of the in-plane resistivity anisotropy in hole-doped iron pnictides. Nat Commun 2013; 4:1914. [DOI: 10.1038/ncomms2933] [Citation(s) in RCA: 95] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2012] [Accepted: 04/26/2013] [Indexed: 11/09/2022] Open
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16
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Persistent high-energy spin excitations in iron-pnictide superconductors. Nat Commun 2013; 4:1470. [DOI: 10.1038/ncomms2428] [Citation(s) in RCA: 89] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2012] [Accepted: 01/02/2013] [Indexed: 11/08/2022] Open
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17
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Wang M, Zhang C, Lu X, Tan G, Luo H, Song Y, Wang M, Zhang X, Goremychkin E, Perring T, Maier T, Yin Z, Haule K, Kotliar G, Dai P. Doping dependence of spin excitations and its correlations with high-temperature superconductivity in iron pnictides. Nat Commun 2013; 4:2874. [PMID: 24301219 PMCID: PMC3863972 DOI: 10.1038/ncomms3874] [Citation(s) in RCA: 87] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2013] [Accepted: 11/05/2013] [Indexed: 11/16/2022] Open
Abstract
High-temperature superconductivity in iron pnictides occurs when electrons and holes are doped into their antiferromagnetic parent compounds. Since spin excitations may be responsible for electron pairing and superconductivity, it is important to determine their electron/hole-doping evolution and connection with superconductivity. Here we use inelastic neutron scattering to show that while electron doping to the antiferromagnetic BaFe₂As₂ parent compound modifies the low-energy spin excitations and their correlation with superconductivity (<50 meV) without affecting the high-energy spin excitations (>100 meV), hole-doping suppresses the high-energy spin excitations and shifts the magnetic spectral weight to low-energies. In addition, our absolute spin susceptibility measurements for the optimally hole-doped iron pnictide reveal that the change in magnetic exchange energy below and above T(c) can account for the superconducting condensation energy. These results suggest that high-T(c) superconductivity in iron pnictides is associated with both the presence of high-energy spin excitations and a coupling between low-energy spin excitations and itinerant electrons.
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Affiliation(s)
- Meng Wang
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- These authors contributed equally to this work
| | - Chenglin Zhang
- Department of Physics and Astronomy, Rice University, Houston, Texas 77005, USA
- Department of Physics and Astronomy, The University of Tennessee, Knoxville, Tennessee 37996-1200, USA
- These authors contributed equally to this work
| | - Xingye Lu
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- Department of Physics and Astronomy, The University of Tennessee, Knoxville, Tennessee 37996-1200, USA
- These authors contributed equally to this work
| | - Guotai Tan
- Department of Physics and Astronomy, The University of Tennessee, Knoxville, Tennessee 37996-1200, USA
| | - Huiqian Luo
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Yu Song
- Department of Physics and Astronomy, Rice University, Houston, Texas 77005, USA
- Department of Physics and Astronomy, The University of Tennessee, Knoxville, Tennessee 37996-1200, USA
| | - Miaoyin Wang
- Department of Physics and Astronomy, The University of Tennessee, Knoxville, Tennessee 37996-1200, USA
| | - Xiaotian Zhang
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - E.A. Goremychkin
- ISIS Facility, Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire OX11 0QX, UK
| | - T.G. Perring
- ISIS Facility, Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire OX11 0QX, UK
| | - T.A. Maier
- Center for Nanophase Materials Sciences and Computer Science and Mathematics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6494, USA
| | - Zhiping Yin
- Department of Physics, Rutgers University, Piscataway, New Jersey 08854, USA
| | - Kristjan Haule
- Department of Physics, Rutgers University, Piscataway, New Jersey 08854, USA
| | - Gabriel Kotliar
- Department of Physics, Rutgers University, Piscataway, New Jersey 08854, USA
| | - Pengcheng Dai
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- Department of Physics and Astronomy, Rice University, Houston, Texas 77005, USA
- Department of Physics and Astronomy, The University of Tennessee, Knoxville, Tennessee 37996-1200, USA
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18
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Shan L, Gong J, Wang YL, Shen B, Hou X, Ren C, Li C, Yang H, Wen HH, Li S, Dai P. Evidence of a spin resonance mode in the iron-based superconductor Ba(0.6)K(0.4)Fe2As2 from scanning tunneling spectroscopy. PHYSICAL REVIEW LETTERS 2012; 108:227002. [PMID: 23003642 DOI: 10.1103/physrevlett.108.227002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/03/2011] [Indexed: 06/01/2023]
Abstract
We used high-resolution scanning tunneling spectroscopy to study the hole-doped iron pnictide superconductor Ba(0.6)K(0.4)Fe(2)As(2) (T(c)=38 K). Features of a bosonic excitation (mode) are observed in the measured quasiparticle density of states. The bosonic features are intimately associated with the superconducting order parameter and have a mode energy of ~14 meV, similar to the spin resonance measured by inelastic neutron scattering. These results indicate a strong electron-spin excitation coupling in iron pnictide superconductors, similar to that in high-T(c) copper oxide superconductors.
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Affiliation(s)
- Lei Shan
- National Laboratory for Superconductivity, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China.
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