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Zhang H, Zhao J, Niu C, Zou L, Zeng Z, Wang X. Structural, electronic and magnetic properties of TlFeSe 2under high pressure. J Phys Condens Matter 2021; 33:415702. [PMID: 34289462 DOI: 10.1088/1361-648x/ac16ac] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/19/2021] [Accepted: 07/21/2021] [Indexed: 06/13/2023]
Abstract
The high-pressure (HP) properties of TlFeSe2are investigated based on the first-principles calculations combined with structure-searching method. The low-pressureC2/mphase will transform into the orthorhombicPnmaphase at 2 GPa, with 8% volume collapse, the insulator-metal transition and the bicollinear antiferromagnetic-to-nonmagnetic spin-crossover. At pressure higher than 8 GPa, the HPC2/mphase will become the ground state. BothPnmaphase and HPC2/mphase are constituted by one-dimensional chains of edge-sharing FeSe5tetragonal pyramids. Pressuring decrease the Se-Se bond length giving rise to the transition from [Se2]3-to [Se2]2-. Negative charge transfer causes the Fe2+with ∼2 μBmagnetic moment at ambient pressure and the nonmagnetic Fe1.5+at higher pressure. The Fermi surfaces of HP phases are also discussed.
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Affiliation(s)
- Hanxing Zhang
- Key Laboratory of Materials Physics, Institute of Solid State Physics, HFIPS, Chinese Academy of Sciences, Hefei 230031, People's Republic of China
- University of Science and Technology of China, Hefei 230026, People's Republic of China
| | - Jing Zhao
- Key Laboratory of Materials Physics, Institute of Solid State Physics, HFIPS, Chinese Academy of Sciences, Hefei 230031, People's Republic of China
- University of Science and Technology of China, Hefei 230026, People's Republic of China
| | - Caoping Niu
- Key Laboratory of Materials Physics, Institute of Solid State Physics, HFIPS, Chinese Academy of Sciences, Hefei 230031, People's Republic of China
- University of Science and Technology of China, Hefei 230026, People's Republic of China
| | - Liangjian Zou
- Key Laboratory of Materials Physics, Institute of Solid State Physics, HFIPS, Chinese Academy of Sciences, Hefei 230031, People's Republic of China
- University of Science and Technology of China, Hefei 230026, People's Republic of China
| | - Zhi Zeng
- Key Laboratory of Materials Physics, Institute of Solid State Physics, HFIPS, Chinese Academy of Sciences, Hefei 230031, People's Republic of China
- University of Science and Technology of China, Hefei 230026, People's Republic of China
| | - Xianlong Wang
- Key Laboratory of Materials Physics, Institute of Solid State Physics, HFIPS, Chinese Academy of Sciences, Hefei 230031, People's Republic of China
- University of Science and Technology of China, Hefei 230026, People's Republic of China
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2
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Llovo IF, Carballeira C, Sóñora D, Pereiro A, Ponte JJ, Salem-Sugui S, Sefat AS, Mosqueira J. Multiband effects on the upper critical field angular dependence of 122-family iron pnictide superconductors. Sci Rep 2021; 11:11526. [PMID: 34075106 PMCID: PMC8169784 DOI: 10.1038/s41598-021-90858-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2021] [Accepted: 05/13/2021] [Indexed: 11/09/2022] Open
Abstract
Detailed measurements of the in-plane resistivity were performed in a high-quality Ba([Formula: see text])[Formula: see text] ([Formula: see text]) single crystal, in magnetic fields up to 9 T and with different orientations [Formula: see text] relative to the crystal c axis. A significant [Formula: see text] rounding is observed just above the superconducting critical temperature [Formula: see text] due to Cooper pairs created by superconducting fluctuations. These data are analyzed in terms of a generalization of the Aslamazov-Larkin approach, that extends its applicability to high reduced-temperatures and magnetic fields. This method allows us to carry out a criterion-independent determination of the angular dependence of the upper critical field, [Formula: see text]. In spite of the relatively small anisotropy of this compound, it is found that [Formula: see text] presents a significant deviation from the single-band 3D anisotropic Ginzburg-Landau (3D-aGL) approach, particularly for large [Formula: see text] (typically above [Formula: see text]). These results are interpreted in terms of the multiband nature of these materials, in contrast with other proposals for similar [Formula: see text] anomalies. Our results are also consistent with an effective anisotropy factor almost temperature independent near [Formula: see text], a result that differs from the ones obtained by using a single-band model.
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Affiliation(s)
- I F Llovo
- QMatterPhotonics Research Group, Departamento de Física de Partículas, Universidade de Santiago de Compostela, 15782, Santiago de Compostela, Spain
| | - C Carballeira
- QMatterPhotonics Research Group, Departamento de Física de Partículas, Universidade de Santiago de Compostela, 15782, Santiago de Compostela, Spain
| | - D Sóñora
- QMatterPhotonics Research Group, Departamento de Física de Partículas, Universidade de Santiago de Compostela, 15782, Santiago de Compostela, Spain
| | - A Pereiro
- QMatterPhotonics Research Group, Departamento de Física de Partículas, Universidade de Santiago de Compostela, 15782, Santiago de Compostela, Spain
| | - J J Ponte
- Unidade de Magnetosusceptibilidade, RIAIDT, Universidade de Santiago de Compostela, 15782, Santiago de Compostela, Spain
| | - S Salem-Sugui
- Instituto de Fisica, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, 21941-972, Brazil
| | - A S Sefat
- Oak Ridge National Laboratory, Oak Ridge, TN, 87831, USA
| | - J Mosqueira
- QMatterPhotonics Research Group, Departamento de Física de Partículas, Universidade de Santiago de Compostela, 15782, Santiago de Compostela, Spain.
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3
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Koch RJ, Sinclair R, McDonnell MT, Yu R, Abeykoon M, Tucker MG, Tsvelik AM, Billinge SJL, Zhou HD, Yin WG, Bozin ES. Dual Orbital Degeneracy Lifting in a Strongly Correlated Electron System. Phys Rev Lett 2021; 126:186402. [PMID: 34018766 DOI: 10.1103/physrevlett.126.186402] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/29/2020] [Accepted: 03/29/2021] [Indexed: 06/12/2023]
Abstract
The local structure of NaTiSi_{2}O_{6} is examined across its Ti-dimerization orbital-assisted Peierls transition at 210 K. An atomic pair distribution function approach evidences local symmetry breaking preexisting far above the transition. The analysis unravels that, on warming, the dimers evolve into a short range orbital degeneracy lifted (ODL) state of dual orbital character, persisting up to at least 490 K. The ODL state is correlated over the length scale spanning ∼6 sites of the Ti zigzag chains. Results imply that the ODL phenomenology extends to strongly correlated electron systems.
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Affiliation(s)
- R J Koch
- Condensed Matter Physics and Materials Science Division, Brookhaven National Laboratory, Upton, New York 11973, USA
| | - R Sinclair
- Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37996, USA
| | - M T McDonnell
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - R Yu
- Condensed Matter Physics and Materials Science Division, Brookhaven National Laboratory, Upton, New York 11973, USA
| | - M Abeykoon
- Photon Sciences Division, Brookhaven National Laboratory, Upton, New York 11973, USA
| | - M G Tucker
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - A M Tsvelik
- Condensed Matter Physics and Materials Science Division, Brookhaven National Laboratory, Upton, New York 11973, USA
| | - S J L Billinge
- Condensed Matter Physics and Materials Science Division, Brookhaven National Laboratory, Upton, New York 11973, USA
- Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027, USA
| | - H D Zhou
- Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37996, USA
| | - W-G Yin
- Condensed Matter Physics and Materials Science Division, Brookhaven National Laboratory, Upton, New York 11973, USA
| | - E S Bozin
- Condensed Matter Physics and Materials Science Division, Brookhaven National Laboratory, Upton, New York 11973, USA
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Maji TK, Vaibhav K, Hawaldar R, Adarsh KV, Pal SK, Karmakar D. Intriguing electronic and optical prospects of FCC bimetallic two-dimensional heterostructures: epsilon near-zero behavior in UV-Vis range. Phys Chem Chem Phys 2020; 22:16314-16324. [PMID: 32647839 DOI: 10.1039/d0cp00951b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A higher superconducting critical temperature and large-area epsilon-near-zero systems are two long-standing goals of the scientific community, having an explicit relationship with the correlated electrons in localized orbitals. Motivated by the recent experimental findings of the strongly correlated phenomena in nanostructures of simple Drude metallic systems, we have theoretically investigated some potential bimetallic FCC combinations having close resemblance with the experimental systems. The explored systems include the large-area interface to the embedded and doped two-dimensional (2D) combinatorial nanostructures. Using different effective single-particle first-principles approaches encompassing density functional theory (DFT), time-dependent DFT (TDDFT), phonon and DFT-coupled quantum transport, we propose some interesting correlated prospects of potential bimetallic nanostructures like Au/Ag and Pt/Pd. For the 2D doped and embedded nanostructures of these systems, the DFT-calculated non-trivial band-structures indicate the interfacial morphology-induced band localization. The calculated Fermi-surface topology of the nanostructures and the corresponding nesting behavior may be emblematic to the presence of instabilities, such as charge density waves. The optical attributes extracted from the TDDFT calculations result in near-zero behavior of both real and imaginary parts of the dynamical dielectric response in the ultra-violet to visible (UV-Vis) optical range. In addition, low-energy intra-band plasmonic oscillations, as present for individual metallic surfaces, are completely suppressed for the embedded and doped nanostructures. The TDDFT-derived electron-energy loss spectra manifest the survival of only inter-band transitions. The presence of soft phonons and dynamic instabilities is observed from the phonon-dispersion of the nanostructured systems. Quantum transport calculations on the simplest possible device made out of these bimetallic systems reveal the generation of highly transmitting pockets over the cross-sectional area for some selected device geometry. We envisage that, if scrutinized experimentally, such systems may unveil many fascinating interdisciplinary aspects of orbital chemistry, physics and optics, promoting their relevant applications in many diverse fields.
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Affiliation(s)
- Tuhin Kumar Maji
- Department of Chemical Biological and Macromolecular Sciences, S.N. Bose National Centre for Basics Sciences, Salt Lake, Sector 3, Kolkata 700106, India
| | - Kumar Vaibhav
- Computer Division, Bhabha Atomic Research Centre, Trombay 400085, India
| | - Ranjit Hawaldar
- Centre for Materials for Electronics Technology, Off Pashan Road, Panchwati, Pune-411008, India
| | - K V Adarsh
- Department of Physics, Indian Institute of Science Education and Research, Bhopal 462066, India
| | - Samir Kumar Pal
- Department of Chemical Biological and Macromolecular Sciences, S.N. Bose National Centre for Basics Sciences, Salt Lake, Sector 3, Kolkata 700106, India
| | - Debjani Karmakar
- Technical Physics Division, Bhabha Atomic Research Centre, Trombay 400085, India.
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5
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Lazarević N, Hackl R. Fluctuations and pairing in Fe-based superconductors: light scattering experiments. J Phys Condens Matter 2020; 32:413001. [PMID: 32272462 DOI: 10.1088/1361-648x/ab8849] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/14/2019] [Accepted: 04/09/2020] [Indexed: 06/11/2023]
Abstract
Inelastic scattering of visible light (Raman effect) offers a window into properties of correlated metals such as spin, electron and lattice dynamics as well as their mutual interactions. In this review we focus on electronic and spin excitations in Fe-based pnictides and chalcogenides, in particular but not exclusively superconductors. After a general introduction to the basic theory including the selection rules for the various scattering processes we provide an overview over the major experimental results. In the superconducting state below the transition temperatureTcthe pair-breaking effect can be observed, and the gap energies may be derived and associated with the gaps on the electron and hole bands. In spite of the similarities of the overall band structures the results are strongly dependent on the family and may even change qualitatively within one family. In some of the compounds strong collective modes appear belowTc. In Ba1-xKxFe2As2, which has the most isotropic gap of all Fe-based superconductors, there are indications that these modes are exciton-like states appearing in the presence of a hierarchy of pairing tendencies. The strong in-gap modes observed in Co-doped NaFeAs are interpreted in terms of quadrupolar orbital excitations which become undamped in the superconducting state. The doping dependence of the scattering intensity in Ba(Fe1-xCox)2As2is associated with a nematic resonance above a quantum critical point and interpreted in terms of a critical enhancement at the maximalTc. In the normal state the response from particle-hole excitations reflects the resistivity. In addition, there are strongly temperature-dependent contributions from presumably critical fluctuations in the energy range ofkBTwhich can be compared to the elastic properties. Currently it is not settled whether the fluctuations observed by light scattering are related to spin or charge. Another controversy relates to putative two-magnon excitations, typically in the energy range below 0.5 eV. Whereas this response presumably originates from charge excitations in most of the Fe-based compounds theory and experiment suggest that the excitations in the 60 meV range in FeSe stem from localized spins in a nearly frustrated system.
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Affiliation(s)
- N Lazarević
- Center for Solid State Physics and New Materials, Institute of Physics Belgrade, University of Belgrade, Pregrevica 118, 11080 Belgrade, Serbia
| | - R Hackl
- Walther Meissner Institut, Bayerische Akademie der Wissenschaften, 85748 Garching, Germany
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6
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Bozin ES, Yin WG, Koch RJ, Abeykoon M, Hor YS, Zheng H, Lei HC, Petrovic C, Mitchell JF, Billinge SJL. Local orbital degeneracy lifting as a precursor to an orbital-selective Peierls transition. Nat Commun 2019; 10:3638. [PMID: 31409783 PMCID: PMC6692321 DOI: 10.1038/s41467-019-11372-w] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2019] [Accepted: 07/09/2019] [Indexed: 11/25/2022] Open
Abstract
Fundamental electronic principles underlying all transition metal compounds are the symmetry and filling of the d-electron orbitals and the influence of this filling on structural configurations and responses. Here we use a sensitive local structural technique, x-ray atomic pair distribution function analysis, to reveal the presence of fluctuating local-structural distortions at high temperature in one such compound, CuIr2S4. We show that this hitherto overlooked fluctuating symmetry-lowering is electronic in origin and will modify the energy-level spectrum and electronic and magnetic properties. The explanation is a local, fluctuating, orbital-degeneracy-lifted state. The natural extension of our result would be that this phenomenon is likely to be widespread amongst diverse classes of partially filled nominally degenerate d-electron systems, with potentially broad implications for our understanding of their properties. A common feature of many transition metal materials is global symmetry breaking at low temperatures. Here the authors show that such materials are characterized by fluctuating symmetry-lowering distortions that exist pre-formed in higher temperature phases with greater average symmetry.
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Affiliation(s)
- E S Bozin
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, NY, 11973, USA.
| | - W G Yin
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, NY, 11973, USA
| | - R J Koch
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, NY, 11973, USA
| | - M Abeykoon
- Photon Sciences Division, Brookhaven National Laboratory, Upton, NY, 11973, USA
| | - Y S Hor
- Materials Science Division, Argonne National Laboratory, Argonne, IL, 60439, USA.,Department of Physics, Missouri University of Science and Technology, Rolla, MO, 65409, USA
| | - H Zheng
- Materials Science Division, Argonne National Laboratory, Argonne, IL, 60439, USA
| | - H C Lei
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, NY, 11973, USA.,Department of Physics and Beijing Key Laboratory of Opto-electronic Functional Materials and Micro-nano Devices, Renmin University of China, 100872, Beijing, China
| | - C Petrovic
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, NY, 11973, USA
| | - J F Mitchell
- Materials Science Division, Argonne National Laboratory, Argonne, IL, 60439, USA
| | - S J L Billinge
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, NY, 11973, USA. .,Department of Applied Physics and Applied Mathematics, Columbia University, New York, NY, 10027, USA.
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7
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Svitlyk V, Garbarino G, Rosa AD, Pomjakushina E, Krzton-Maziopa A, Conder K, Nunez-Regueiro M, Mezouar M. High-pressure polymorphism of BaFe 2Se 3. J Phys Condens Matter 2019; 31:085401. [PMID: 30530951 DOI: 10.1088/1361-648x/aaf777] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
BaFe2Se3 is a potential superconductor material exhibiting transition at 11 K and ambient pressure. Here we extended the structural and performed electrical resistivity measurements on this compound up to 51 GPa and 20 GPa, respectively, in order to distinguish if the superconductivity in this sample is intrinsic to the BaFe2Se3 phase or if it is originating from minor FeSe impurities that show a similar superconductive transition temperature. The electrical resistance measurements as a function of pressure show that at 5 GPa the superconducting transition is observed at around 10 K, similar to the one previously observed for this sample at ambient pressure. This indicates that the superconductivity in this sample is most likely intrinsic to the BaFe2Se3 phase and not to FeSe with T c > 20 K at these pressures. Further increase in pressure suppressed the superconductive signal and the sample remained in an insulating state up to the maximum achieved pressure of 20 GPa. Single-crystal and powder x-ray diffraction measurements revealed two structural transformations in BaFe2Se3: a second order transition above 3.5 GPa from Pnma (CsAg2I3-type structure) to Cmcm (CsCu2Cl3-type structure) and a first order transformation at 16.6 GPa. Here, γ-BaFe2Se3 transforms into δ-BaFe2Se3 (Cmcm, CsCu2Cl3-type average structure) via a first order phase transition mechanism. This transition is characterized by a significant shortening of the b lattice parameter of γ-BaFe2Se3 (17%) and accompanied by an anisotropic expansion in the orthogonal ac plane at the transition point.
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Affiliation(s)
- V Svitlyk
- European Synchrotron Radiation Facility, 38000 Grenoble, France
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8
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Lee TH, Chubukov A, Miao H, Kotliar G. Pairing Mechanism in Hund's Metal Superconductors and the Universality of the Superconducting Gap to Critical Temperature Ratio. Phys Rev Lett 2018; 121:187003. [PMID: 30444397 DOI: 10.1103/physrevlett.121.187003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/23/2018] [Revised: 08/20/2018] [Indexed: 06/09/2023]
Abstract
We analyze a simple model containing the physical ingredients of a Hund's metal, the local spin fluctuations with power-law correlators, (Ω_{0}/|Ω|)^{γ}, with γ greater than one, interacting with electronic quasiparticles. While the critical temperature and the gap change significantly with varying parameters, the 2Δ_{max}/k_{B}T_{c} remains close to twice the BCS value in agreement with experimental observations in the iron-based superconductors (FeSC).
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Affiliation(s)
- Tsung-Han Lee
- Physics and Astronomy Department, Rutgers University, Piscataway, New Jersey 08854, USA
| | - Andrey Chubukov
- School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota 55455, USA
| | - Hu Miao
- Brookhaven National Laboratory, Upton, New York 11973, USA
| | - Gabriel Kotliar
- Physics and Astronomy Department, Rutgers University, Piscataway, New Jersey 08854, USA
- Brookhaven National Laboratory, Upton, New York 11973, USA
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Whangbo MH, Deng S, Köhler J, Simon A. Interband Electron Pairing for Superconductivity from the Breakdown of the Born-Oppenheimer Approximation. Chemphyschem 2018; 19:3191-3195. [PMID: 30296352 DOI: 10.1002/cphc.201800738] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2018] [Indexed: 11/09/2022]
Abstract
The origin of interband electron pairing, responsible for enhancing superconductivity, and the factors controlling its strength were examined. We show that interband electron pairing is a natural consequence of breaking down the Born-Oppenheimer approximation during electron-phonon interactions. Its strength is determined by the pair-state excitations around the Fermi surfaces that take place to form a superconducting state. Fermi surfaces favorable for the pairing were found, and the implications of this observation are discussed.
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Affiliation(s)
- Myung-Hwan Whangbo
- Department of Chemistry, North Carolina State University, Raleigh, NC 27695-8204, USA
- State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter (FJIRSM), Chinese Academy of Sciences (CAS), Fuzhou, 350002, China
- State key Laboratory of Crystal Materials, Shandong University, Jinan, 250100, China
| | - Shuiquan Deng
- State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter (FJIRSM), Chinese Academy of Sciences (CAS), Fuzhou, 350002, China
| | - Jürgen Köhler
- State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter (FJIRSM), Chinese Academy of Sciences (CAS), Fuzhou, 350002, China
- Max-Planck-Institute for Solid State Research, Heisenbergstr. 1, D-70569, Stuttgart, Germany
| | - Arndt Simon
- Max-Planck-Institute for Solid State Research, Heisenbergstr. 1, D-70569, Stuttgart, Germany
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Kim S, Yi S, Oh M, Jang BG, Nam W, Yoo YC, Lee M, Jeon H, Zoh I, Lee H, Zhang C, Kim KH, Seo J, Shim JH, Chae J, Kuk Y. Surface reconstruction and charge modulation in BaFe 2As 2 superconducting film. J Phys Condens Matter 2018; 30:315001. [PMID: 29916822 DOI: 10.1088/1361-648x/aacd85] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Whether or not epitaxially grown superconducting films have the same bulk-like superconducting properties is an important concern. We report the structure and the electronic properties of epitaxially grown Ba(Fe1-x Co x )2As2 films using scanning tunneling microscopy and scanning tunneling spectroscopy (STS). This film showed a different surface structure, [Formula: see text]R45° reconstruction, from those of as-cleaved surfaces from bulk crystals. The electronic structure of the grown film is different from that in bulk, and it is notable that the film exhibits the same superconducting transport properties. We found that the superconducting gap at the surface is screened at the Ba layer surface in STS measurements, and the charge density wave was observed at the surface in sample in the superconducting state.
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Affiliation(s)
- S Kim
- Department of Physics and Astronomy, Seoul National University, Seoul 08826, Republic of Korea
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11
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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}. Phys Rev Lett 2018; 120:267003. [PMID: 30004765 DOI: 10.1103/physrevlett.120.267003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [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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12
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Singh DK. Spin-wave excitations in the spin-density wave state of doped iron pnictides. J Phys Condens Matter 2017; 29:415601. [PMID: 28869752 DOI: 10.1088/1361-648x/aa7e13] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
We investigate spin-wave excitations in the spin-density wave state of doped iron pnictides within a five-orbital model. We find that the excitations along ([Formula: see text]) → ([Formula: see text]) are very sensitive to dopings whereas they do not exhibit a similar sensitivity along ([Formula: see text]) → ([Formula: see text]). Secondly, the ellipticity of the elliptical ring-like excitations around ([Formula: see text]) is also very much dependent on doping. Thirdly, the spin-wave spectral weight shifts towards the low-energy region as it moves away from zero doping. We find several features to be in qualitative agreement with the inelastic neutron-scattering measurements for the doped pnictides.
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Affiliation(s)
- Dheeraj Kumar Singh
- Harish-Chandra Research Institute, Chhatnag Road, Jhunsi, Allahabad 211019, India. Homi Bhabha National Institute, Training School Complex, Anushakti Nagar, Mumbai 400085, India
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13
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Ptok A, Kapcia KJ, Cichy A, Oleś AM, Piekarz P. Magnetic Lifshitz transition and its consequences in multi-band iron-based superconductors. Sci Rep 2017; 7:41979. [PMID: 28165043 PMCID: PMC5292748 DOI: 10.1038/srep41979] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2016] [Accepted: 01/04/2017] [Indexed: 11/09/2022] Open
Abstract
In this paper we address Lifshitz transition induced by applied external magnetic field in a case of iron-based superconductors, in which a difference between the Fermi level and the edges of the bands is relatively small. We introduce and investigate a two-band model with intra-band pairing in the relevant parameters regime to address a generic behaviour of a system with hole-like and electron-like bands in external magnetic field. Our results show that two Lifshitz transitions can develop in analysed systems and the first one occurs in the superconducting phase and takes place at approximately constant magnetic field. The chosen sets of the model parameters can describe characteristic band structure of iron-based superconductors and thus the obtained results can explain the experimental observations in FeSe and Co-doped BaFe2As2 compounds.
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Affiliation(s)
- Andrzej Ptok
- Institute of Physics, Maria Curie-Skłodowska University, Plac M. Skłodowskiej-Curie 1, PL-20031 Lublin, Poland.,Institute of Nuclear Physics, Polish Academy of Sciences, ul. E. Radzikowskiego 152, PL-31342 Kraków, Poland
| | - Konrad J Kapcia
- Institute of Physics, Polish Academy of Sciences, Aleja Lotników 32/46, PL-02668 Warsaw, Poland
| | - Agnieszka Cichy
- Institut für Physik, Johannes Gutenberg-Universität Mainz, Staudingerweg 9, D-55099 Mainz, Germany
| | - Andrzej M Oleś
- Marian Smoluchowski Institute of Physics, Jagiellonian University, ul. prof. S. Łojasiewicza 11, PL-30348 Kraków, Poland.,Max Planck Institute for Solid State Research, Heisenbergstrasse 1, D-70569 Stuttgart, Germany
| | - Przemysław Piekarz
- Institute of Nuclear Physics, Polish Academy of Sciences, ul. E. Radzikowskiego 152, PL-31342 Kraków, Poland
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14
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Kyung WS, Huh SS, Koh YY, Choi KY, Nakajima M, Eisaki H, Denlinger JD, Mo SK, Kim C, Kim YK. Enhanced superconductivity in surface-electron-doped iron pnictide Ba(Fe 1.94Co 0.06) 2As 2. Nat Mater 2016; 15:1233-1236. [PMID: 27525569 DOI: 10.1038/nmat4728] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/21/2015] [Accepted: 07/14/2016] [Indexed: 06/06/2023]
Abstract
The superconducting transition temperature (TC) in a FeSe monolayer on SrTiO3 is enhanced up to 100 K (refs ,,,). High TC is also found in bulk iron chalcogenides with similar electronic structure to that of monolayer FeSe, which suggests that higher TC may be achieved through electron doping, pushing the Fermi surface (FS) topology towards leaving only electron pockets. Such an observation, however, has been limited to chalcogenides, and is in contrast to the iron pnictides, for which the maximum TC is achieved with both hole and electron pockets forming considerable FS nesting instability. Here, we report angle-resolved photoemission characterization revealing a monotonic increase of TC from 24 to 41.5 K upon surface doping on optimally doped Ba(Fe1-xCox)2As2. The doping changes the overall FS topology towards that of chalcogenides through a rigid downward band shift. Our findings suggest that higher electron doping and concomitant changes in FS topology are favourable conditions for the superconductivity, not only for iron chalcogenides, but also for iron pnictides.
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Affiliation(s)
- W S Kyung
- Institute of Physics and Applied Physics, Yonsei University, Seoul 120-749, Republic of Korea
- Center for Correlated Electron Systems, Institute for Basic Science, Seoul 151-742, Republic of Korea
- Department of Physics and Astronomy, Seoul National University, Seoul 151-747, Republic of Korea
| | - S S Huh
- Institute of Physics and Applied Physics, Yonsei University, Seoul 120-749, Republic of Korea
- Center for Correlated Electron Systems, Institute for Basic Science, Seoul 151-742, Republic of Korea
- Department of Physics and Astronomy, Seoul National University, Seoul 151-747, Republic of Korea
| | - Y Y Koh
- Pohang Accelerator Laboratory, Pohang University of Science and Technology, Pohang 790-784, Republic of Korea
| | - K-Y Choi
- Center for Correlated Electron Systems, Institute for Basic Science, Seoul 151-742, Republic of Korea
- Department of Physics and Astronomy, Seoul National University, Seoul 151-747, Republic of Korea
| | - M Nakajima
- Department of Physics, Osaka University 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan
| | - H Eisaki
- National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba 305-8568, Japan
| | - J D Denlinger
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - S-K Mo
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - C Kim
- Center for Correlated Electron Systems, Institute for Basic Science, Seoul 151-742, Republic of Korea
- Department of Physics and Astronomy, Seoul National University, Seoul 151-747, Republic of Korea
| | - Y K Kim
- Center for Correlated Electron Systems, Institute for Basic Science, Seoul 151-742, Republic of Korea
- Department of Physics and Astronomy, Seoul National University, Seoul 151-747, Republic of Korea
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
- Department of Physics, KAIST, Daejon 34141, Republic of Korea
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15
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Guguchia Z, Amato A, Kang J, Luetkens H, Biswas PK, Prando G, von Rohr F, Bukowski Z, Shengelaya A, Keller H, Morenzoni E, Fernandes RM, Khasanov R. Direct evidence for a pressure-induced nodal superconducting gap in the Ba0.65Rb0.35Fe2As2 superconductor. Nat Commun 2015; 6:8863. [PMID: 26548650 PMCID: PMC4667685 DOI: 10.1038/ncomms9863] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2015] [Accepted: 10/12/2015] [Indexed: 11/09/2022] Open
Abstract
The superconducting gap structure in iron-based high-temperature superconductors (Fe-HTSs) is non-universal. In contrast to other unconventional superconductors, in the Fe-HTSs both d-wave and extended s-wave pairing symmetries are close in energy. Probing the proximity between these very different superconducting states and identifying experimental parameters that can tune them is of central interest. Here we report high-pressure muon spin rotation experiments on the temperature-dependent magnetic penetration depth in the optimally doped nodeless s-wave Fe-HTS Ba0.65Rb0.35Fe2As2. Upon pressure, a strong decrease of the penetration depth in the zero-temperature limit is observed, while the superconducting transition temperature remains nearly constant. More importantly, the low-temperature behaviour of the inverse-squared magnetic penetration depth, which is a direct measure of the superfluid density, changes qualitatively from an exponential saturation at zero pressure to a linear-in-temperature behaviour at higher pressures, indicating that hydrostatic pressure promotes the appearance of nodes in the superconducting gap.
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Affiliation(s)
- Z Guguchia
- Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institute, CH-5232 Villigen, Switzerland
| | - A Amato
- Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institute, CH-5232 Villigen, Switzerland
| | - J Kang
- School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota 55455, USA
| | - H Luetkens
- Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institute, CH-5232 Villigen, Switzerland
| | - P K Biswas
- Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institute, CH-5232 Villigen, Switzerland
| | - G Prando
- Leibniz-Institut für Festkörper- und Werkstoffforschung (IFW) Dresden, D-01171 Dresden, Germany
| | - F von Rohr
- Physik-Institut der Universität Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland
| | - Z Bukowski
- Institute of Low Temperature and Structure Research, Polish Academy of Sciences, 50-422 Wroclaw, Poland
| | - A Shengelaya
- Department of Physics, Tbilisi State University, Chavchavadze 3, GE-0128 Tbilisi, Georgia
| | - H Keller
- Physik-Institut der Universität Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland
| | - E Morenzoni
- Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institute, CH-5232 Villigen, Switzerland
| | - Rafael M Fernandes
- School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota 55455, USA
| | - R Khasanov
- Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institute, CH-5232 Villigen, Switzerland
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16
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Richard P, Qian T, Ding H. ARPES measurements of the superconducting gap of Fe-based superconductors and their implications to the pairing mechanism. J Phys Condens Matter 2015; 27:293203. [PMID: 26153847 DOI: 10.1088/0953-8984/27/29/293203] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Its direct momentum sensitivity confers to angle-resolved photoemission spectroscopy (ARPES) a unique perspective in investigating the superconducting gap of multi-band systems. In this review we discuss ARPES studies on the superconducting gap of high-temperature Fe-based superconductors. We show that while Fermi-surface-driven pairing mechanisms fail to provide a universal scheme for the Fe-based superconductors, theoretical approaches based on short-range interactions lead to a more robust and universal description of superconductivity in these materials. Our findings are also discussed in the broader context of unconventional superconductivity.
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Affiliation(s)
- P Richard
- Beijing National Laboratory for Condensed Matter Physics, and 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
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17
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Cheng J, Dong P, Xu W, Liu S, Chu W, Chen X, Wu Z. Charge redistribution and a shortening of the Fe--As bond at the quantum critical point of SmO1-xFxFeAs. J Synchrotron Radiat 2015; 22:1030-1034. [PMID: 26134807 DOI: 10.1107/s1600577515008450] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/27/2015] [Accepted: 04/29/2015] [Indexed: 06/04/2023]
Abstract
Many researchers have pointed out that there is a quantum critical point (QCP) in the F-doped SmOFeAs system. In this paper, the electronic structure and local structure of the superconductive FeAs layer in SmO(1-x)FxFeAs as a function of the F-doping concentration have been investigated using Fe and As K-edge X-ray absorption spectroscopy. Experiments performed on the X-ray absorption near-edge structure showed that in the vicinity of the QCP the intensity of the pre-edge feature at the Fe-edge decreases continuously, while there is a striking rise of the shoulder-peak at the As edge, suggesting the occurrence of charge redistribution near the QCP. Further analysis on the As K-edge extended X-ray absorption fine structure demonstrated that the charge redistribution originates mostly from a shortening of the Fe-As bond at the QCP. An evident relationship between the mysterious QCP and the fundamental Fe-As bond was established, providing new insights on the interplay between QCP, charge dynamics and the local structural Fe-As bond in Fe-based superconductors.
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Affiliation(s)
- Jie Cheng
- College of Science, Nanjing University of Posts and Telecommunications, Nanjing, Jiangsu 210023, People's Republic of China
| | - Peng Dong
- Information Construction and Management Office, Nanjing University of Posts and Telecommunications, Nanjing, Jiangsu 210023, People's Republic of China
| | - Wei Xu
- Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing, 100049, People's Republic of China
| | - Shengli Liu
- Nanjing University (Suzhou) High-Tech Institute, Suzhou, Jiangsu 215123, People's Republic of China
| | - Wangsheng Chu
- Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing, 100049, People's Republic of China
| | - Xianhui Chen
- Hefei National Laboratory for Physical Science at Microscale and Department of Physics, University of Science and Technology of China, Hefei 230026, People's Republic of China
| | - Ziyu Wu
- Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing, 100049, People's Republic of China
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18
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Cantoni C, Mitchell JE, May AF, McGuire MA, Idrobo JC, Berlijn T, Dagotto E, Chisholm MF, Zhou W, Pennycook SJ, Sefat AS, Sales BC. Orbital occupancy and charge doping in iron-based superconductors. Adv Mater 2014; 26:6193-6198. [PMID: 25070045 DOI: 10.1002/adma.201401518] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/03/2014] [Revised: 06/05/2014] [Indexed: 06/03/2023]
Abstract
The intrinsic Fe local magnetic moment and Fe orbital occupations of iron-based superconductors are unveiled through the local, real-space capability of aberration-corrected scanning transmission electron microscopy/electron energy loss spectroscopy (STEM/EELS). Although the ordering of Fe moments needs to be suppressed for superconductivity to arise, the local, fluctuating Fe magnetic moment is enhanced near optimal superconductivity.
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Affiliation(s)
- Claudia Cantoni
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
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19
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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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20
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Xia M, Jiao WH, Ye ZR, Ge QQ, Zhang Y, Jiang J, Peng R, Shen XP, Fan Q, Cao GH, Zhang T, Xie BP, Feng DL. Electronic structure of Eu(Fe0.79Ru0.21)2As2 studied by angle-resolved photoemission spectroscopy. J Phys Condens Matter 2014; 26:265701. [PMID: 24912631 DOI: 10.1088/0953-8984/26/26/265701] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Eu(Fe(0.79)Ru(0.21))2As2 is suggested to be a nodeless superconductor based on the empirical correlation between pnictogen height (hPn) and superconducting gap behavior, in contrast to BaFe2(As(0.7)P(0.3))2 and Ba(Fe(0.65)Ru(0.35))2As2. We studied the low-lying electronic structure of Eu(Fe(0.79)Ru(0.21))2As2 with angle-resolved photoemission spectroscopy (ARPES). By photon energy dependence and polarization dependence measurements, we resolved the band structure in the three-dimensional momentum space and determined the orbital character of each band. In particular, we found that the dz2 -originated ζ band does not contribute spectral weight to the Fermi surface around Z, unlike BaFe2(As(0.7)P(0.3))2 and Ba(Fe(0.65)Ru(0.35))2As2. Since BaFe2(As(0.7)P(0.3))2 and Ba(Fe(0.65)Ru(0.35))2As2 are nodal superconductors and their hPn's are less than 1.33 Å, while the hPn of Eu(Fe(0.79)Ru(0.21))2As2 is larger than 1.33 Å, our results provide more evidence for a direct relationship between nodes, dz2 orbital character and hPn. Our results help to provide an understanding of the nodal superconductivity in iron-based superconductors.
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21
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Abstract
The new family of unconventional iron-based superconductors discovered in 2006 immediately relieved their copper-based high-temperature predecessors as the most actively studied superconducting compounds in the world. The experimental and theoretical effort made in order to unravel the mechanism of superconductivity in these materials has been overwhelming. Although our understanding of their microscopic properties has been improving steadily, the pairing mechanism giving rise to superconducting transition temperatures up to 55 K remains elusive. And yet the hope is strong that these materials, which possess a drastically different electronic structure but similarly high transition temperatures compared to the copper-based compounds, will shed essential new light onto the several-decade-old problem of unconventional superconductivity. In this work we review the current understanding of the itinerant-charge-carrier dynamics in the iron-based superconductors and parent compounds largely based on the optical conductivity data the community has gleaned over the past seven years using such experimental techniques as reflectivity, ellipsometry, and terahertz transmission measurements and analyze the implications of these studies for the microscopic properties of the iron-based materials as well as the mechanism of superconductivity therein.
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22
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Kuo HH, Fisher IR. Effect of disorder on the resistivity anisotropy near the electronic nematic phase transition in pure and electron-doped BaFe(2)As(2). Phys Rev Lett 2014; 112:227001. [PMID: 24949785 DOI: 10.1103/physrevlett.112.227001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/04/2013] [Indexed: 06/03/2023]
Abstract
We show that the strain-induced resistivity anisotropy in the tetragonal state of the representative underdoped Fe arsenides BaFe_{2}As_{2}, Ba(Fe_{1-x}Co_{x})_{2}As_{2} and Ba(Fe_{1-x}Ni_{x})_{2}As_{2} is independent of disorder over a wide range of defect and impurity concentrations. This result demonstrates that the anisotropy in the in-plane resistivity in the paramagnetic orthorhombic state of this material is not due to elastic scattering from anisotropic defects. Conversely, our result can be most easily understood if the resistivity anisotropy arises primarily from an intrinsic anisotropy in the electronic structure.
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Affiliation(s)
- Hsueh-Hui Kuo
- Geballe Laboratory for Advanced Materials and Department of Materials Science and Engineering, Stanford University, Stanford, California 94305, USA and Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA
| | - Ian R Fisher
- Geballe Laboratory for Advanced Materials and Department of Applied Physics, Stanford University, Stanford, California 94305, USA and Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA
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23
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Sunagawa M, Ishiga T, Tsubota K, Jabuchi T, Sonoyama J, Iba K, Kudo K, Nohara M, Ono K, Kumigashira H, Matsushita T, Arita M, Shimada K, Namatame H, Taniguchi M, Wakita T, Muraoka Y, Yokoya T. Characteristic two-dimensional Fermi surface topology of high-Tc iron-based superconductors. Sci Rep 2014; 4:4381. [PMID: 24625746 PMCID: PMC3953724 DOI: 10.1038/srep04381] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2013] [Accepted: 02/24/2014] [Indexed: 11/09/2022] Open
Abstract
Unconventional Cooper pairing originating from spin or orbital fluctuations has been proposed for iron-based superconductors. Such pairing may be enhanced by quasi-nesting of two-dimensional electron and hole-like Fermi surfaces (FS), which is considered an important ingredient for superconductivity at high critical temperatures (high-Tc). However, the dimensionality of the FS varies for hole and electron-doped systems, so the precise importance of this feature for high-Tc materials remains unclear. Here we demonstrate a phase of electron-doped CaFe2As2 (La and P co-doped CaFe2As2) with Tc = 45 K, which is the highest Tc found for the AEFe2As2 bulk superconductors (122-type; AE = Alkaline Earth), possesses only cylindrical hole- and electron-like FSs. This result indicates that FS topology consisting only of two-dimensional sheets is characteristic of both hole- and electron-doped 122-type high-Tc superconductors.
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Affiliation(s)
- Masanori Sunagawa
- 1] The Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan [2] Research Laboratory for Surface Science, Okayama University, 3-1-1 Tsushima-naka, Okayama 700-8530, Japan
| | - Toshihiko Ishiga
- 1] The Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan [2] Research Laboratory for Surface Science, Okayama University, 3-1-1 Tsushima-naka, Okayama 700-8530, Japan
| | - Koji Tsubota
- 1] The Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan [2] Research Laboratory for Surface Science, Okayama University, 3-1-1 Tsushima-naka, Okayama 700-8530, Japan
| | - Taihei Jabuchi
- 1] The Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan [2] Research Laboratory for Surface Science, Okayama University, 3-1-1 Tsushima-naka, Okayama 700-8530, Japan
| | - Junki Sonoyama
- 1] The Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan [2] Research Laboratory for Surface Science, Okayama University, 3-1-1 Tsushima-naka, Okayama 700-8530, Japan
| | - Keita Iba
- 1] The Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan [2] Department of Physics, Okayama University, Okayama 700-8530, Japan
| | - Kazutaka Kudo
- 1] The Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan [2] Department of Physics, Okayama University, Okayama 700-8530, Japan
| | - Minoru Nohara
- 1] The Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan [2] Department of Physics, Okayama University, Okayama 700-8530, Japan
| | - Kanta Ono
- Institute for Material Structure Science, High Energy Accelerator Research Organization, Tsukuba, Ibaraki 305-0801
| | - Hiroshi Kumigashira
- Institute for Material Structure Science, High Energy Accelerator Research Organization, Tsukuba, Ibaraki 305-0801
| | - Tomohiro Matsushita
- Japan Synchrotron Radiation Research Institute (JASRI)/SPring-8, 1-1-1 Kouto, Sayo, Hyogo 679-5198, Japan
| | - Masashi Arita
- Hiroshima Synchrotron Radiation Center, Hiroshima University, Higashi-Hiroshima, Hiroshima 739-0046, Japan
| | - Kenya Shimada
- Hiroshima Synchrotron Radiation Center, Hiroshima University, Higashi-Hiroshima, Hiroshima 739-0046, Japan
| | - Hirofumi Namatame
- Hiroshima Synchrotron Radiation Center, Hiroshima University, Higashi-Hiroshima, Hiroshima 739-0046, Japan
| | - Masaki Taniguchi
- Hiroshima Synchrotron Radiation Center, Hiroshima University, Higashi-Hiroshima, Hiroshima 739-0046, Japan
| | - Takanori Wakita
- 1] The Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan [2] Research Laboratory for Surface Science, Okayama University, 3-1-1 Tsushima-naka, Okayama 700-8530, Japan
| | - Yuji Muraoka
- 1] The Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan [2] Research Laboratory for Surface Science, Okayama University, 3-1-1 Tsushima-naka, Okayama 700-8530, Japan
| | - Takayoshi Yokoya
- 1] The Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan [2] Research Laboratory for Surface Science, Okayama University, 3-1-1 Tsushima-naka, Okayama 700-8530, Japan
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24
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Zhao J, Rotundu CR, Marty K, Matsuda M, Zhao Y, Setty C, Bourret-Courchesne E, Hu J, Birgeneau RJ. Effect of electron correlations on magnetic excitations in the isovalently doped iron-based superconductor Ba(Fe(1-x)Ru(x))(2)As(2). Phys Rev Lett 2013; 110:147003. [PMID: 25167027 DOI: 10.1103/physrevlett.110.147003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/12/2012] [Indexed: 06/03/2023]
Abstract
Magnetic correlations in isovalently doped Ba(Fe(1-x)Ru(x))(2)As(2) (x = 0.25, T(c) = 14.5 K; x = 0.35, T(c) = 20 K) are studied by elastic and inelastic neutron scattering techniques. A relatively large superconducting spin gap accompanied by a weak resonance mode is observed in the superconducting state in both samples. In the normal state, the magnetic excitation intensity is dramatically reduced with increasing Ru doping toward the optimally doped regime. Our results favor that the weakening of the electron-electron correlations by Ru doping is responsible for the dampening of the resonance mode, as well as the suppression of the normal state antiferromagnetic correlations near the optimally doped regime in this system.
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Affiliation(s)
- Jun Zhao
- Department of Physics, and Laboratory of Advanced Materials, State Key Laboratory of Surface Physics, Fudan University, Shanghai 200433, People's Republic of China and Department of Physics, University of California, Berkeley, California 94720, USA and Miller Institute for Basic Research in Science, Berkeley, California 94720, USA
| | - C R Rotundu
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - K Marty
- Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - M Matsuda
- Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - Y Zhao
- NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA and Department of Materials Science and Engineering, University of Maryland, College Park, Maryland 20742, USA
| | - C Setty
- Department of Physics, Purdue University, West Lafayette, Indiana 47907, USA
| | - E Bourret-Courchesne
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Jiangping Hu
- Department of Physics, Purdue University, West Lafayette, Indiana 47907, USA
| | - R J Birgeneau
- Department of Physics, University of California, Berkeley, California 94720, USA and Department of Materials Science and Engineering, University of California, Berkeley, California 94720, USA
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25
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Ideta S, Yoshida T, Nishi I, Fujimori A, Kotani Y, Ono K, Nakashima Y, Yamaichi S, Sasagawa T, Nakajima M, Kihou K, Tomioka Y, Lee CH, Iyo A, Eisaki H, Ito T, Uchida S, Arita R. Dependence of carrier doping on the impurity potential in transition-metal-substituted FeAs-based superconductors. Phys Rev Lett 2013; 110:107007. [PMID: 23521287 DOI: 10.1103/physrevlett.110.107007] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/08/2012] [Revised: 01/14/2013] [Indexed: 06/01/2023]
Abstract
In order to examine to what extent the rigid-band-like electron doping scenario is applicable to the transition metal-substituted Fe-based superconductors, we have performed angle-resolved photoemission spectroscopy studies of Ba(Fe(1-x)Ni(x))(2)As(2) (Ni-122) and Ba(Fe(1-x)Cu(x))(2)As(2) (Cu-122), and compared the results with Ba(Fe(1-x)Co(x))(2)As(2) (Co-122). We find that Ni 3d-derived features are formed below the Fe 3d band and that Cu 3d-derived ones further below it. The electron and hole Fermi surface (FS) volumes are found to increase and decrease with substitution, respectively, qualitatively consistent with the rigid-band model. However, the total extra electron number estimated from the FS volumes (the total electron FS volume minus the total hole FS volume) is found to decrease in going from Co-, Ni-, to Cu-122 for a fixed nominal extra electron number, that is, the number of electrons that participate in the formation of FS decreases with increasing impurity potential. We find that the Néel temperature T(N) and the critical temperature T(c) maximum are determined by the FS volumes rather than the nominal extra electron concentration or the substituted atom concentration.
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Affiliation(s)
- S Ideta
- Department of Physics, University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan
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26
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Koepernik K, Johnston S, van Heumen E, Huang Y, Kaas J, Goedkoop JB, Golden MS, van den Brink J. Surface adatom conductance filtering in scanning tunneling spectroscopy of co-doped BaFe2As2 iron pnictide superconductors. Phys Rev Lett 2012; 109:127001. [PMID: 23005977 DOI: 10.1103/physrevlett.109.127001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/22/2012] [Indexed: 06/01/2023]
Abstract
We establish in a combination of ab initio theory and experiments that the tunneling process in scanning tunneling microscopy or spectroscopy on the A-122 iron pnictide superconductors-in this case BaFe(2-x)Co(x)As(2)-involves a strong adatom filtering of the differential conductance from the near-E(F) Fe-3d states, which in turn originates from the topmost subsurface Fe layer of the crystal. The calculations show that the dominance of surface Ba-related tunneling pathways leaves fingerprints found in the experimental differential conductance data, including large particle-hole asymmetry and energy-dependent contrast inversion in conductance maps.
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Affiliation(s)
- K Koepernik
- Institute for Theoretical Solid State Physics, IFW Dresden, Germany
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27
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Liu ZH, Richard P, Xu N, Xu G, Li Y, Fang XC, Jia LL, Chen GF, Wang DM, He JB, Qian T, Hu JP, Ding H, Wang SC. Three dimensionality and orbital characters of the Fermi surface in (Tl,Rb)(y)Fe(2-x)Se2. Phys Rev Lett 2012; 109:037003. [PMID: 22861887 DOI: 10.1103/physrevlett.109.037003] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/05/2012] [Indexed: 06/01/2023]
Abstract
We report a comprehensive angle-resolved photoemission spectroscopy study of the tridimensional electronic bands in the recently discovered Fe selenide superconductor ((Tl,Rb)(y)Fe(2-x)Se2 (T(c)=32 K). We determined the orbital characters and the k(z) dependence of the low energy electronic structure by tuning the polarization and the energy of the incident photons. We observed a small 3D electron Fermi surface pocket near the Brillouin zone center and a 2D like electron Fermi surface pocket near the zone boundary. The photon energy dependence, the polarization analysis and the local-density approximation calculations suggest a significant contribution from the Se 4p(z) and Fe 3d(xy) orbitals to the small electron pocket. We argue that the emergence of Se 4p(z) states might be the cause of the different magnetic properties between Fe chalcogenides and Fe pnictides.
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Affiliation(s)
- Z-H Liu
- Department of Physics, Renmin University, Beijing, 100872, People's Republic of China
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28
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Ying TP, Chen XL, Wang G, Jin SF, Zhou TT, Lai XF, Zhang H, Wang WY. Observation of superconductivity at 30~46 K in A(x)Fe₂Se₂(A = Li, Na, Ba, Sr, Ca, Yb, and Eu). Sci Rep 2012; 2:426. [PMID: 22645642 DOI: 10.1038/srep00426] [Citation(s) in RCA: 265] [Impact Index Per Article: 22.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2012] [Accepted: 05/10/2012] [Indexed: 11/08/2022] Open
Abstract
New iron selenide superconductors by intercalating smaller-sized alkali metals (Li, Na) and alkaline earths using high-temperature routes have been pursued ever since the discovery of superconductivity at about 30 K in KFe₂Se₂, but all have failed so far. Here we demonstrate that a series of superconductors with enhanced T(c) = 30∼46 K can be obtained by intercalating metals, Li, Na, Ba, Sr, Ca, Yb, and Eu in between FeSe layers by the ammonothermal method at room temperature. Analysis on their powder X-ray diffraction patterns reveals that all the main phases can be indexed based on body-centered tetragonal lattices with a∼3.755-3.831 Å while c∼15.99-20.54 Å. Resistivities show the corresponding sharp transitions at 45 K and 39 K for NaFe₂Se₂ and Ba₀.₈Fe₂Se₂, respectively, confirming their bulk superconductivity. These findings provide a new starting point for studying the properties of these superconductors and an effective synthetic route for the exploration of new superconductors as well.
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29
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Das T, Balatsky AV. Testing the sign-changing superconducting gap in iron-based superconductors with quasiparticle interference and neutron scattering. J Phys Condens Matter 2012; 24:182201. [PMID: 22498771 DOI: 10.1088/0953-8984/24/18/182201] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
We present a phenomenological calculation of the quasiparticle interference (QPI) pattern and inelastic neutron scattering (INS) spectra in iron-pnictide and layered iron-selenide compounds by using material specific band structure and superconducting (SC) gap properties. As both the QPI and the INS spectra arise due to scattering of the Bogolyubov quasiparticles, they exhibit a one-to-one correspondence of the scattering vectors and the energy scales. We show that these two spectroscopies complement each other in such a way that a comparative study allows one to extract quantitative and unambiguous information about the underlying pairing structure and the phase of the SC gap. Due to the nodeless and isotropic nature of the SC gaps, both the QPI and INS maps are concentrated at only two energies in pnictide (two SC gaps) and one energy in iron-selenide, while the associated scattering vectors q for scattering of sign-changing and same sign of the SC gaps change between these spectroscopies. The results presented, particularly for the newly discovered iron-selenide compounds, can be used to test the nodeless d-wave pairing in this class of high temperature superconductor.
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Affiliation(s)
- Tanmoy Das
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM 87545, USA.
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30
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Umezawa K, Li Y, Miao H, Nakayama K, Liu ZH, Richard P, Sato T, He JB, Wang DM, Chen GF, Ding H, Takahashi T, Wang SC. Unconventional anisotropic s-wave superconducting gaps of the LiFeAs iron-pnictide superconductor. Phys Rev Lett 2012; 108:037002. [PMID: 22400776 DOI: 10.1103/physrevlett.108.037002] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/14/2011] [Indexed: 05/31/2023]
Abstract
We have performed high-resolution angle-resolved photoemission spectroscopy on Fe-based superconductor LiFeAs (T(c)=18 K). We reveal multiple nodeless superconducting (SC) gaps with 2Δ/k(B)T(c) ratios varying from 2.8 to 6.4, depending on the Fermi surface (FS). We also succeeded in directly observing a gap anisotropy along the FS with magnitude up to ~30%. The anisotropy is fourfold symmetric with an antiphase between the hole and electron FSs, suggesting complex anisotropic interactions for the SC pairing. The observed momentum dependence of the SC gap offers an excellent opportunity to investigate the underlying pairing mechanism.
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Affiliation(s)
- K Umezawa
- Department of Physics, Tohoku University, Sendai 980-8578, Japan
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31
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Zhang X, Wang Y, Ma Y. High pressure structures of “111” type iron-based superconductors predicted from first-principles. Phys Chem Chem Phys 2012; 14:15029-35. [DOI: 10.1039/c2cp42734f] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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32
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Park JT, Friemel G, Li Y, Kim JH, Tsurkan V, Deisenhofer J, Krug von Nidda HA, Loidl A, Ivanov A, Keimer B, Inosov DS. Magnetic resonant mode in the low-energy spin-excitation spectrum of superconducting Rb2Fe4Se5 single crystals. Phys Rev Lett 2011; 107:177005. [PMID: 22107568 DOI: 10.1103/physrevlett.107.177005] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/01/2011] [Indexed: 05/31/2023]
Abstract
We have studied the low-energy spin-excitation spectrum of the single-crystalline Rb(2)Fe(4)Se(5) superconductor (T(c)=32 K) by means of inelastic neutron scattering. In the superconducting state, we observe a magnetic resonant mode centered at an energy of ℏω(res)=14 meV and at the (0.5 0.25 0.5) wave vector (unfolded Fe-sublattice notation), which differs from the ones characterizing magnetic resonant modes in other iron-based superconductors. Our finding suggests that the 245-iron selenides are unconventional superconductors with a sign-changing order parameter, in which bulk superconductivity coexists with the √5×√5 magnetic superstructure. The estimated ratios of ℏω(res)/k(B)T(c)≈5.1±0.4 and ℏω(res)/2Δ≈0.7±0.1, where Δ is the superconducting gap, indicate moderate pairing strength in this compound, similar to that in optimally doped 1111 and 122 pnictides.
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Affiliation(s)
- J T Park
- Max-Planck-Institut für Festkörperforschung, Heisenbergstrasse 1, 70569 Stuttgart, Germany
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33
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Qian T, Wang XP, Jin WC, Zhang P, Richard P, Xu G, Dai X, Fang Z, Guo JG, Chen XL, Ding H. Absence of a holelike fermi surface for the iron-based K0.8F1.7Se2 superconductor revealed by angle-resolved photoemission spectroscopy. Phys Rev Lett 2011; 106:187001. [PMID: 21635119 DOI: 10.1103/physrevlett.106.187001] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/30/2010] [Indexed: 05/30/2023]
Abstract
We have performed an angle-resolved photoemission spectroscopy study of the new iron-based superconductor K(0.8)Fe(1.7)Se(2) (T(c)∼30 K). Clear band dispersion is observed with the overall bandwidth renormalized by a factor of 2.5 compared to our local density approximation calculations, indicating relatively strong correlation effects. Only an electronlike band crosses the Fermi energy, forming a nearly circular Fermi surface (FS) at M (π, 0). The holelike band at Γ sinks ∼90 meV below the Fermi energy, with an indirect band gap of 30 meV, to the bottom of the electronlike band. The observed FS topology in this superconductor favors (π, π) inter-FS scattering between the electronlike FSs at the M points, in sharp contrast to other iron-based superconductors which favor (π, 0) inter-FS scattering between holelike and electronlike FSs.
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Affiliation(s)
- T Qian
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, China
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34
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Das T, Balatsky AV. Two energy scales in the magnetic resonance spectrum of electron and hole doped pnictide superconductors. Phys Rev Lett 2011; 106:157004. [PMID: 21568605 DOI: 10.1103/physrevlett.106.157004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/22/2010] [Indexed: 05/30/2023]
Abstract
We argue that a multiband superconductor with sign-changing gaps may have multiple spin resonances. We calculate the RPA-based spin resonance spectra of a pnictide superconductor by using the five-band tight-binding model or angle-resolved photoemission spectroscopy Fermi surface (FS) and experimental values of superconducting gaps. The resonance spectra split in both energy and momenta due to the effects of multiband and multiple gaps in s(±) pairing; the higher energy peak appears around the commensurate momenta due to scattering between α-FS to γ/δ-FS pockets. The second resonance is incommensurate, coming from β-FS to γ/δ-FS scatterings, and its q vector is doping-dependent and, hence, on the FS topology. Energies of both resonances ω(res)(1,2) are strongly doping-dependent and are proportional to the gap amplitudes at the contributing FSs.
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Affiliation(s)
- Tanmoy Das
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
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35
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Zhang Y, Yang LX, Xu M, Ye ZR, Chen F, He C, Xu HC, Jiang J, Xie BP, Ying JJ, Wang XF, Chen XH, Hu JP, Matsunami M, Kimura S, Feng DL. Nodeless superconducting gap in A(x)Fe2Se2 (A=K,Cs) revealed by angle-resolved photoemission spectroscopy. Nat Mater 2011; 10:273-7. [PMID: 21358648 DOI: 10.1038/nmat2981] [Citation(s) in RCA: 110] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/07/2011] [Accepted: 02/01/2011] [Indexed: 05/15/2023]
Abstract
Pairing symmetry is a fundamental property that characterizes a superconductor. For the iron-based high-temperature superconductors, an s(±)-wave pairing symmetry has received increasing experimental and theoretical support. More specifically, the superconducting order parameter is an isotropic s-wave type around a particular Fermi surface, but it has opposite signs between the hole Fermi surfaces at the zone centre and the electron Fermi surfaces at the zone corners. Here we report the low-energy electronic structure of the newly discovered superconductors, A(x)Fe(2)Se(2) (A=K,Cs) with a superconducting transition temperature (Tc) of about 30 K. We found A(x)Fe(2)Se(2) (A=K,Cs) is the most heavily electron-doped among all iron-based superconductors. Large electron Fermi surfaces are observed around the zone corners, with an almost isotropic superconducting gap of ~10.3 meV, whereas there is no hole Fermi surface near the zone centre, which demonstrates that interband scattering or Fermi surface nesting is not a necessary ingredient for the unconventional superconductivity in iron-based superconductors. Thus, the sign change in the s(±) pairing symmetry driven by the interband scattering as suggested in many weak coupling theories becomes conceptually irrelevant in describing the superconducting state here. A more conventional s-wave pairing is probably a better description.
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36
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Yoshida T, Nishi I, Ideta S, Fujimori A, Kubota M, Ono K, Kasahara S, Shibauchi T, Terashima T, Matsuda Y, Ikeda H, Arita R. Two-dimensional and three-dimensional Fermi surfaces of superconducting BaFe2(As(1-x)P(x))2 and their nesting properties revealed by angle-resolved photoemission spectroscopy. Phys Rev Lett 2011; 106:117001. [PMID: 21469889 DOI: 10.1103/physrevlett.106.117001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/12/2010] [Indexed: 05/30/2023]
Abstract
We have studied the three-dimensional shapes of the Fermi surfaces (FSs) of BaFe(2)(As(1-x)P(x))(2) (x=0.38), where superconductivity is induced by isovalent P substitution and by angle-resolved photoemission spectroscopy. Moderately strong electron mass enhancement has been identified for both the electron and hole FSs. Among two observed hole FSs, the nearly two-dimensional one shows good nesting with the outer two-dimensional electron FS, but its orbital character is different from the outer electron FS. The three-dimensional hole FS shows poor nesting with the electron FSs. The present results suggest that the three dimensionality and the difference in the orbital character weaken FS nesting while partial nesting among the outer electron FSs of d(xy) character and/or that within the three-dimensional hole FS becomes dominant, which may lead to the nodal superconductivity.
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Affiliation(s)
- T Yoshida
- Department of Physics, University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan
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37
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Teague ML, Drayna GK, Lockhart GP, Cheng P, Shen B, Wen HH, Yeh NC. Measurement of a sign-changing two-gap superconducting phase in electron-doped Ba(Fe(1-x)Co(x))2As2 single crystals using scanning tunneling spectroscopy. Phys Rev Lett 2011; 106:087004. [PMID: 21405593 DOI: 10.1103/physrevlett.106.087004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/13/2010] [Indexed: 05/30/2023]
Abstract
Scanning tunneling spectroscopic studies of Ba(Fe(1-x)Co(x))(2)As(2) (x=0.06, 0.12) single crystals reveal direct evidence for predominantly two-gap superconductivity. These gaps decrease with increasing temperature and vanish above the superconducting transition T(c). The two-gap nature and the slightly doping- and energy-dependent quasiparticle scattering interferences near the wave vectors (±π, 0) and (0, ±π) are consistent with sign-changing s-wave superconductivity. The excess zero-bias conductance and the large gap-to-T(c) ratios suggest dominant unitary impurity scattering.
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Affiliation(s)
- M L Teague
- Department of Physics, California Institute of Technology, Pasadena, California 91125, USA
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38
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Tortello M, Daghero D, Ummarino GA, Stepanov VA, Jiang J, Weiss JD, Hellstrom EE, Gonnelli RS. Multigap superconductivity and strong electron-boson coupling in Fe-based superconductors: a point-contact Andreev-reflection study of Ba(Fe(1-x)Co(x))2As2 single crystals. Phys Rev Lett 2010; 105:237002. [PMID: 21231497 DOI: 10.1103/physrevlett.105.237002] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/04/2010] [Indexed: 05/30/2023]
Abstract
Directional point-contact Andreev-reflection measurements in Ba(Fe(1-x)Co(x))2As2 single crystals (T(c) = 24.5 K) indicate the presence of two superconducting gaps with no line nodes on the Fermi surface. The point-contact Andreev-reflection spectra also feature additional structures related to the electron-boson interaction, from which the characteristic boson energy Ω(b)(T) is obtained, very similar to the spin-resonance energy observed in neutron scattering experiments. Both the gaps and the additional structures can be reproduced within a three-band s ± Eliashberg model by using an electron-boson spectral function peaked at Ω(0) = 12 meV ≃ Ω(b)(0).
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Affiliation(s)
- M Tortello
- Dipartimento di Fisica, Politecnico di Torino, 10129 Torino, Italy
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39
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Analytis JG, Chu JH, McDonald RD, Riggs SC, Fisher IR. Enhanced Fermi-surface nesting in superconducting BaFe2(As(1-x)P(x))2 revealed by the de Haas-van Alphen effect. Phys Rev Lett 2010; 105:207004. [PMID: 21231258 DOI: 10.1103/physrevlett.105.207004] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/05/2010] [Indexed: 05/30/2023]
Abstract
The three-dimensional Fermi-surface morphology of superconducting BaFe2(As0.37P0.63)2 with T(c)=9 K is determined using the de Haas-van Alphen effect. The inner electron pocket has a similar area and k(z) interplane warping to the observed hole pocket, revealing that the Fermi surfaces are geometrically well nested in the (π,π) direction. These results are in stark contrast to the fermiology of the nonsuperconducting phosphides (x=1), and therefore suggest an important role for nesting in pnictide superconductivity.
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Affiliation(s)
- J G Analytis
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA
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40
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Nakayama K, Sato T, Richard P, Kawahara T, Sekiba Y, Qian T, Chen GF, Luo JL, Wang NL, Ding H, Takahashi T. Angle-resolved photoemission spectroscopy of the iron-chalcogenide superconductor Fe1.03Te0.7Se0.3: strong coupling behavior and the universality of interband scattering. Phys Rev Lett 2010; 105:197001. [PMID: 21231191 DOI: 10.1103/physrevlett.105.197001] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/05/2009] [Revised: 03/10/2010] [Indexed: 05/30/2023]
Abstract
We have performed angle-resolved photoemission spectroscopy of the iron-chalcogenide superconductor Fe1.03Te0.7Se0.3 to investigate the electronic structure relevant to superconductivity. We observed a holelike Fermi surface (FS) and an electronlike FS at the Brillouin zone center and corner, respectively, which are nearly nested by the Q∼(π,π) wave vector. We do not find evidence for the nesting instability with Q∼(π+δ,0) reminiscent of the antiferromagnetic order in the parent compound Fe1+yTe. We have observed an isotropic superconducting (SC) gap along the holelike FS with the gap size Δ of ∼4 meV (2Δ/kBTc ∼ 7), demonstrating the strong-coupling superconductivity. The observed similarity of low-energy electronic excitations between iron-chalcogenides and iron-arsenides strongly suggests that common interactions which involve Q∼(π,π) scattering are responsible for the SC pairing.
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Affiliation(s)
- K Nakayama
- Department of Physics, Tohoku University, Sendai 980-8578, Japan
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41
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Zhang Y, Yang LX, Chen F, Zhou B, Wang XF, Chen XH, Arita M, Shimada K, Namatame H, Taniguchi M, Hu JP, Xie BP, Feng DL. Out-of-plane momentum and symmetry-dependent energy gap of the pnictide Ba0.6K0.4Fe2As2 superconductor revealed by angle-resolved photoemission spectroscopy. Phys Rev Lett 2010; 105:117003. [PMID: 20867600 DOI: 10.1103/physrevlett.105.117003] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/20/2010] [Indexed: 05/29/2023]
Abstract
The three-dimensional band structure and superconducting gap of Ba0.6K0.4Fe2As2 are studied with angle-resolved photoemission spectroscopy. In contrast with previous results, we have identified three holelike Fermi surface sheets near the zone center with sizable out-of-plane or kz dispersion. The superconducting gap on certain Fermi surface sheets shows significant kz dependence. Moreover, the superconducting gap sizes are different at the same Fermi momentum for two bands with different spatial symmetries (one odd, one even). Our results further reveal the three-dimensional and orbital-dependent structure of the superconducting gap in iron pnictides, which facilitates the understanding of momentum-integrated measurements and provides a distinct test for theories.
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Affiliation(s)
- Y Zhang
- State Key Laboratory of Surface Physics, Department of Physics, Fudan University, Shanghai 200433, People's Republic of China
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42
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Brouet V, Rullier-Albenque F, Marsi M, Mansart B, Aichhorn M, Biermann S, Faure J, Perfetti L, Taleb-Ibrahimi A, Le Fèvre P, Bertran F, Forget A, Colson D. Significant reduction of electronic correlations upon isovalent Ru substitution of BaFe2As2. Phys Rev Lett 2010; 105:087001. [PMID: 20868126 DOI: 10.1103/physrevlett.105.087001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/25/2010] [Indexed: 05/29/2023]
Abstract
We investigate Ba(Fe0.65Ru0.35)2As2, a compound in which superconductivity appears at the expense of magnetism, by transport measurements and angle resolved photoemission spectroscopy. By resolving the different Fermi surface pockets and deducing from their volumes the number of hole and electron carriers, we show that Ru induces neither hole nor electron doping. However, the Fermi surface pockets are about twice larger than in BaFe2As2. A change of sign of the Hall coefficient with decreasing temperature evidences the contribution of both carriers to the transport. Fermi velocities increase significantly with respect to BaFe2As2, suggesting a reduction of correlation effects.
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Affiliation(s)
- V Brouet
- Laboratoire de Physique des Solides, Université Paris Sud, CNRS-UMR8502, 91405 Orsay, France
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Kumar P, Kumar A, Saha S, Muthu DVS, Prakash J, Waghmare UV, Ganguli AK, Sood AK. Temperature-dependent Raman study of a CeFeAsO(0.9)F(0.1) superconductor: crystal field excitations, phonons and their coupling. J Phys Condens Matter 2010; 22:255402. [PMID: 21393798 DOI: 10.1088/0953-8984/22/25/255402] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
We report temperature-dependent Raman spectra of CeFeAsO(0.9)F(0.1) from 4 to 300 K in the spectral range of 60-1800 cm(-1) and interpret them using estimates of phonon frequencies obtained from first-principles density functional calculations. We find evidence for strong coupling between the phonons and crystal field excitations; in particular the Ce(3 + ) crystal field excitation at 432 cm(-1) couples strongly with the E(g) oxygen vibration at 389 cm(-1). Below the superconducting transition temperature, the phonon mode near 280 cm(-1) shows softening, signaling its coupling with the superconducting gap. The ratio of the superconducting gap to T(c), thus estimated to be ~10, suggests CeFeAsO(0.9)F(0.1) to be a strong coupling superconductor. In addition, two high frequency modes observed at 1342 and 1600 cm(-1) are attributed to electronic Raman scattering from the (x(2)-y(2)) to xz /yz d-orbitals of Fe.
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Affiliation(s)
- Pradeep Kumar
- Department of Physics, Indian Institute of Science, Bangalore, India
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Abstract
In this review, we present a summary of experimental studies of magnetism in Fe-based superconductors. The doping dependent phase diagram shows strong similarities to the generic phase diagram of the cuprates. Parent compounds exhibit magnetic order together with a structural phase transition, both of which are progressively suppressed with doping, allowing superconductivity to emerge. The stripe-like spin arrangement of Fe moments in the magnetically ordered state shows identical in-plane structure for the RFeAsO (R = rare earth) and AFe(2)As(2) (A = Sr, Ca, Ba, Eu and K) parent compounds, notably different than the spin configuration of the cuprates. Interestingly, Fe(1 + y)Te orders with a different spin order despite having very similar Fermi surface topology. Studies of the spin dynamics of the parent compounds show that the interactions are best characterized as anisotropic three-dimensional interactions. Despite the room temperature tetragonal structure, analysis of the low temperature spin waves under the assumption of a Heisenberg Hamiltonian indicates strong in-plane anisotropy with a significant next-nearest-neighbor interaction. For the superconducting state, a resonance, localized in both wavevector and energy, is observed in the spin excitation spectrum as for the cuprates. This resonance is observed at a wavevector compatible with a Fermi surface nesting instability independent of the magnetic ordering of the relevant parent compound. The resonance energy (E(r)) scales with the superconducting transition temperature (T(C)) as E(r) ∼ 4.9k(B)T(C), which is consistent with the canonical value of ∼ 5k(B)T(C) observed for the cuprates. Moreover, the relationship between the resonance energy and the superconducting gap, Δ, is similar to that observed for many unconventional superconductors (E(r)/2Δ ∼ 0.64).
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Affiliation(s)
- M D Lumsden
- Neutron Scattering Science Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.
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Sudayama T, Wakisaka Y, Takubo K, Morinaga R, Sato TJ, Arita M, Namatame H, Taniguchi M, Mizokawa T. Band structure of the heavily-electron-doped FeAs-based Ba(Fe,Co)2As2 superconductor suppresses antiferromagnetic correlations. Phys Rev Lett 2010; 104:177002. [PMID: 20482128 DOI: 10.1103/physrevlett.104.177002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/18/2009] [Indexed: 05/29/2023]
Abstract
In the heavily-electron-doped regime of the Ba(Fe,Co)2As2 superconductor, three hole bands at the zone center are observed and two of them reach the Fermi level. The larger hole pocket at the zone center is apparently nested with the smaller electron pocket around the zone corner. However, the (pi,0) Fermi surface reconstruction reported for the hole-doped case is absent in the heavily-electron-doped case. This observation shows that the apparent Fermi surface nesting alone is not enough to enhance the antiferromagnetic correlation as well as the superconducting transition temperature.
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Affiliation(s)
- T Sudayama
- Department of Physics and Department of Complexity Science and Engineering, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8561, Japan
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Abstract
LiCu(2)P(2) and LiFeP have been synthesized by conventional solid-state reaction. LiCu(2)P(2) has a crystal structure similar to that of BaFe(2)As(2); LiFeP has the same crystal structure as that of LiFeAs. Resistivity and magnetization measurements reveal that they become superconductive at 3.5 K for LiCu(2)P(2) and 4.1 K for LiFeP.
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Affiliation(s)
- Jian-Tao Han
- Texas Materials Institute, ETC 9.102, University of Texas at Austin, Austin, Texas 78712, USA
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Dong JK, Zhou SY, Guan TY, Zhang H, Dai YF, Qiu X, Wang XF, He Y, Chen XH, Li SY. Quantum criticality and nodal superconductivity in the FeAs-based superconductor KFe2As2. Phys Rev Lett 2010; 104:087005. [PMID: 20366962 DOI: 10.1103/physrevlett.104.087005] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/04/2010] [Indexed: 05/29/2023]
Abstract
The in-plane resistivity rho and thermal conductivity kappa of the FeAs-based superconductor KFe2As2 single crystal were measured down to 50 mK. We observe non-Fermi-liquid behavior rho(T) approximately T{1.5} at H{c{2}}=5 T, and the development of a Fermi liquid state with rho(T) approximately T{2} when further increasing the field. This suggests a field-induced quantum critical point, occurring at the superconducting upper critical field H{c{2}}. In zero field, there is a large residual linear term kappa{0}/T, and the field dependence of kappa_{0}/T mimics that in d-wave cuprate superconductors. This indicates that the superconducting gaps in KFe2As2 have nodes, likely d-wave symmetry. Such a nodal superconductivity is attributed to the antiferromagnetic spin fluctuations near the quantum critical point.
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Affiliation(s)
- J K Dong
- Department of Physics, Surface Physics Laboratory (National Key Laboratory), and Laboratory of Advanced Materials, Fudan University, Shanghai 200433, China
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Tao Q, Zhu Z, Lin X, Cao G, Xu ZA, Chen G, Luo J, Wang N. A comparative study on the thermoelectric effect of parent oxypnictides LaTAsO (T = Fe, Ni). J Phys Condens Matter 2010; 22:072201. [PMID: 21386374 DOI: 10.1088/0953-8984/22/7/072201] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
The thermopower and Nernst effect were investigated for undoped parent compounds LaFeAsO and LaNiAsO. Both the thermopower and Nernst signal in iron-based LaFeAsO are significantly larger than those in nickel-based LaNiAsO. Furthermore, abrupt changes in both the thermopower and Nernst effect are observed below the structural phase transition temperature and spin-density wave (SDW) type antiferromagnetic (AFM) order temperature in Fe-based LaFeAsO. On the other hand, the Nernst effect is very small in the Ni-based LaNiAsO and it is weakly temperature-dependent, reminiscent of the case in normal metals. We suggest that the effect of SDW order on the spin scattering rate should play an important role in the anomalous temperature dependence of the Hall effect and Nernst effect in LaFeAsO. The contrasting behaviour between the LaFeAsO and LaNiAsO systems implies that the LaFeAsO system is fundamentally different from the LaNiAsO system and this may provide clues to the mechanism of high T(c) superconductivity in Fe-based systems.
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Affiliation(s)
- Qian Tao
- Department of Physics, Zhejiang University, Hangzhou 310027, People's Republic of China
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Martikainen JP, Kinnunen JJ, Törmä P, Pethick CJ. Induced interactions and the superfluid transition temperature in a three-component Fermi gas. Phys Rev Lett 2009; 103:260403. [PMID: 20366298 DOI: 10.1103/physrevlett.103.260403] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/26/2009] [Revised: 12/04/2009] [Indexed: 05/29/2023]
Abstract
We study many-body contributions to the effective interaction between fermions in a three-component Fermi mixture. We find that effective interactions induced by the third component can lead to a phase diagram different from that predicted if interactions with the third component are neglected. As a result, in a confining potential a superfluid shell structure can arise even for equal populations of the components. We also find a critical temperature for the BCS transition in a 6Li mixture which can deviate strongly from the one in a weakly interacting two-component system.
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