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Pandeya RP, Pramanik A, Sakhya AP, Mondal R, Yadav AK, Jha SN, Thamizhavel A, Maiti K. Evolution of local structure and superconductivity in CaFe 2As 2. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2021; 33:19LT01. [PMID: 33556927 DOI: 10.1088/1361-648x/abe44c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/11/2020] [Accepted: 02/08/2021] [Indexed: 06/12/2023]
Abstract
We investigate the evolution of the local structural parameters and their implication in unconventional superconductivity of 122 class of materials employing extended x-ray absorption fine structure studies. The spectral functions near the FeK- and AsK-absorption edges of CaFe2As2and its superconducting composition, CaFe1.9Co0.1As2(Tc= 12 K) exhibit evidence of enhancement of Fe contributions near the Fermi level with Co substitution, which becomes more prominent at low temperatures indicating enhanced role of Fe in the electronic properties with doping. As-Fe and Fe-Fe bondlengths derived from the experimental data reveal evolution with temperature across the magneto-structural transition in the parent compound. The evolution of these parameters in Co-doped superconducting composition is similar to its parent compound although no magneto-structural transition is observed in this system. These results reveal an evidence of doping induced evolution to the proximity to critical behavior and/or strong nematic fluctuations which might be important for superconductivity in this system.
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Affiliation(s)
- Ram Prakash Pandeya
- Department of Condensed Matter Physics and Materials Science, Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai 400 005, India
| | - Arindam Pramanik
- Department of Condensed Matter Physics and Materials Science, Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai 400 005, India
| | - Anup Pradhan Sakhya
- Department of Condensed Matter Physics and Materials Science, Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai 400 005, India
| | - Rajib Mondal
- Department of Condensed Matter Physics and Materials Science, Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai 400 005, India
| | - A K Yadav
- Atomic and Molecular Physics Division, Bhabha Atomic Research Centre, Mumbai 400085, India
| | - S N Jha
- Atomic and Molecular Physics Division, Bhabha Atomic Research Centre, Mumbai 400085, India
| | - A Thamizhavel
- Department of Condensed Matter Physics and Materials Science, Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai 400 005, India
| | - Kalobaran Maiti
- Department of Condensed Matter Physics and Materials Science, Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai 400 005, India
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Förster T, Kraft I, Sheikin I, Bianchi AD, Wosnitza J, Rosner H. Fermi surface of LaFe 2P 2-a detailed density functional study. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2020; 32:025503. [PMID: 31536970 DOI: 10.1088/1361-648x/ab45fa] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Angular-dependent de Haas-van Alphen measurements allow the mapping of Fermi surfaces in great detail with high accuracy. Density functional electronic-structure calculations can be carried out with high precision, but depend crucially on the used structural information and the applied calculational approximations. We report in a detailed study the sensitivity of the calculated electronic band structure of the 122 compound LaFe2P2 on (i) the exact P position in the unit cell, parametrized by a so-called z parameter, and on (ii) the treatment of the La 4f states. Depending on the chosen exchange and correlation-potential approximation, the calculated z parameter varies slightly and corresponding small but distinctive differences in the calculated band structure and Fermi-surface topology appear. Similarly, topology changes appear when the energy of the mostly unoccupied La 4f states is corrected regarding their experimentally observed position. The calculated results are compared to experimental de Haas-van Alphen data. Our findings show a high sensitivity of the calculated band structure on the pnictide z position and the need for an accurate experimental determination of this parameter at low temperatures, and a particular need for a sophisticated treatment of the La 4f states. Thus, this is not only crucial for the special case of LaFe2P2 studied here, but of importance for the precise determination of the band structure of related 122 materials and La containing compounds in general.
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Affiliation(s)
- T Förster
- Hochfeld-Magnetlabor Dresden (HLD-EMFL) and Würzburg-Dresden Cluster of Excellence ct.qmat, Helmholtz-Zentrum Dresden-Rossendorf, 01328 Dresden, Germany
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Kashurnikov VA, Krasavin AV, Zhumagulov YV. Asymptotically Exact Method for Calculating the Density of States of High-temperature Superconductors. CRYSTALLOGR REP+ 2019. [DOI: 10.1134/s1063774519020160] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Pikul AP, Samsel-Czekała M, Chajewski G, Romanova T, Hackemer A, Gorzelniak R, Wiśniewski P, Kaczorowski D. Search for unconventional superconductors among the YTE 2Si 2 compounds (TE = Cr, Co, Ni, Rh, Pd, Pt). JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2017; 29:195602. [PMID: 28323631 DOI: 10.1088/1361-648x/aa6832] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Motivated by the recent discovery of exotic superconductivity in YFe2Ge2 we undertook reinvestigation of formation and physical properties of yttrium-based 1:2:2 silicides. Here we report on syntheses and crystal structures of the YTE 2Si2 compounds with TE = Cr, Co, Ni, Rh, Pd and Pt, and their low-temperature physical properties measurements, supplemented by results of fully relativistic full-potential local-orbital minimum basis band structure calculations. We confirm that most of the members of that family crystallize in a tetragonal ThCr2Si2-type structure (space group I4/mmm) and have three-dimensional Fermi surface, while only one of them (YPt2Si2) forms with a closely-related primitive CaBe2Ge2-type unit cell (space group P4/nmm) and possess quasi-two-dimensional Fermi surface sheets. Physical measurements indicated that BCS-like superconductivity is observed only in YPt2Si2 (T c = 1.54 K) and YPd2Si2 (T c = 0.43 K), while no superconducting phase transition was found in other systems at least down to 0.35 K. Thermal analysis showed no polymorphism in both superconducting phases. No clear relation between the superconductivity and the crystal structure (and dimensionality of the Fermi surface) was observed.
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Affiliation(s)
- A P Pikul
- Institute of Low Temperature and Structure Research, Polish Academy of Sciences, P Nr 1410, 50-950 Wrocław 2, Poland
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6
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van Roekeghem A, Ayral T, Tomczak JM, Casula M, Xu N, Ding H, Ferrero M, Parcollet O, Jiang H, Biermann S. Dynamical correlations and screened exchange on the experimental bench: spectral properties of the cobalt pnictide BaCo2As2. PHYSICAL REVIEW LETTERS 2014; 113:266403. [PMID: 25615361 DOI: 10.1103/physrevlett.113.266403] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/13/2014] [Indexed: 06/04/2023]
Abstract
Understanding the Fermi surface and low-energy excitations of iron or cobalt pnictides is crucial for assessing electronic instabilities such as magnetic or superconducting states. Here, we propose and implement a new approach to compute the low-energy properties of correlated electron materials, taking into account both screened exchange beyond the local density approximation and local dynamical correlations. The scheme allows us to resolve the puzzle of BaCo2As2, for which standard electronic structure techniques predict a ferromagnetic instability not observed in nature.
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Affiliation(s)
- Ambroise van Roekeghem
- Beijing National Laboratory for Condensed Matter Physics, and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China and Centre de Physique Théorique, Ecole Polytechnique, CNRS UMR 7644, 91128 Palaiseau, France
| | - Thomas Ayral
- Centre de Physique Théorique, Ecole Polytechnique, CNRS UMR 7644, 91128 Palaiseau, France and Institut de Physique Théorique (IPhT), CEA, CNRS, URA 2306, 91191 Gif-sur-Yvette, France
| | - Jan M Tomczak
- Institute of Solid State Physics, Vienna University of Technology, A-1040 Vienna, Austria
| | - Michele Casula
- CNRS and Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie, Université Pierre et Marie Curie, case 115, 4 place Jussieu, FR-75252 Paris Cedex 05, France
| | - Nan Xu
- Beijing National Laboratory for Condensed Matter Physics, and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China and Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen, Switzerland
| | - Hong Ding
- Beijing National Laboratory for Condensed Matter Physics, and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China and Collaborative Innovation Center of Quantum Matter, Beijing 100190, China
| | - Michel Ferrero
- Centre de Physique Théorique, Ecole Polytechnique, CNRS UMR 7644, 91128 Palaiseau, France
| | - Olivier Parcollet
- Institut de Physique Théorique (IPhT), CEA, CNRS, URA 2306, 91191 Gif-sur-Yvette, France
| | - Hong Jiang
- College of Chemistry and Molecular Engineering, Peking University, 100871 Beijing, China
| | - Silke Biermann
- Centre de Physique Théorique, Ecole Polytechnique, CNRS UMR 7644, 91128 Palaiseau, France and Collège de France, 11 place Marcelin Berthelot, 75005 Paris, France
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Mannella N. The magnetic moment enigma in Fe-based high temperature superconductors. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2014; 26:473202. [PMID: 25352180 DOI: 10.1088/0953-8984/26/47/473202] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The determination of the most appropriate starting point for the theoretical description of Fe-based materials hosting high-temperature superconductivity remains among the most important unsolved problem in this relatively new field. Most of the work to date has focused on the pnictides, with LaFeAsO, BaFe(2)As(2) and LiFeAs being representative parent compounds of three families known as 1111, 122 and 111, respectively. This topical review examines recent progress in this area, with particular emphasis on the implication of experimental data which have provided evidence for the presence of electron itinerancy and the detection of local spin moments. In light of the results presented, the necessity of a theoretical framework contemplating the presence and the interplay between itinerant electrons and large spin moments is discussed. It is argued that the physics at the heart of the macroscopic properties of pnictides Fe-based high-temperature superconductors appears to be far more complex and interesting than initially predicted.
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Affiliation(s)
- Norman Mannella
- Department of Physics and Astronomy, University of Tennessee, Knoxville, TN,USA
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8
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Avci S, Chmaissem O, Allred J, Rosenkranz S, Eremin I, Chubukov A, Bugaris D, Chung D, Kanatzidis M, Castellan JP, Schlueter J, Claus H, Khalyavin D, Manuel P, Daoud-Aladine A, Osborn R. Magnetically driven suppression of nematic order in an iron-based superconductor. Nat Commun 2014; 5:3845. [DOI: 10.1038/ncomms4845] [Citation(s) in RCA: 138] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2013] [Accepted: 04/08/2014] [Indexed: 11/09/2022] Open
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Biermann S. Dynamical screening effects in correlated electron materials-a progress report on combined many-body perturbation and dynamical mean field theory: 'GW + DMFT'. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2014; 26:173202. [PMID: 24722486 DOI: 10.1088/0953-8984/26/17/173202] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
We give a summary of recent progress in the field of electronic structure calculations for materials with strong electronic Coulomb correlations. The discussion focuses on developments beyond the by now well established combination of density functional and dynamical mean field theory dubbed 'LDA + DMFT'. It is organized around the description of dynamical screening effects in the solid. Indeed, screening in the solid gives rise to dynamical local Coulomb interactions U(ω) (Aryasetiawan et al 2004 Phys. Rev. B 70 195104), and this frequency dependence leads to effects that cannot be neglected in a truly first principles description. We review the recently introduced extension of LDA + DMFT to dynamical local Coulomb interactions 'LDA + U(ω) + DMFT' (Casula et al 2012 Phys. Rev. B 85 035115, Werner et al 2012 Nature Phys. 1745-2481). A reliable description of dynamical screening effects is also a central ingredient of the 'GW + DMFT' scheme (Biermann et al 2003 Phys. Rev. Lett. 90 086402), a combination of many-body perturbation theory in Hedin's GW approximation and dynamical mean field theory. Recently, the first GW + DMFT calculations including dynamical screening effects for real materials have been achieved, with applications to SrV O3 (Tomczak et al 2012 Europhys. Lett. 100 67001, Tomczak et al Phys. Rev. B submitted (available electronically as arXiv:1312.7546)) and adatom systems on surfaces (Hansmann et al 2013 Phys. Rev. Lett. 110 166401). We review these and comment on further perspectives in the field. This review is an attempt to put elements of the original works into the broad perspective of the development of truly first principles techniques for correlated electron materials.
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Affiliation(s)
- Silke Biermann
- Centre de Physique Théorique, CNRS UMR7644, Ecole Polytechnique, F-91128 Palaiseau, France
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Khan SN, Johnson DD. Lifshitz transition and chemical instabilities in Ba(1-x)K(x)Fe2As2 superconductors. PHYSICAL REVIEW LETTERS 2014; 112:156401. [PMID: 24785059 DOI: 10.1103/physrevlett.112.156401] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/11/2013] [Indexed: 06/03/2023]
Abstract
For solid-solution Ba1-xKxFe2As2 Fermi surface evolution is mapped via Bloch spectral functions calculated using density functional theory implemented in Korringa-Kohn-Rostoker multiple scattering theory with the coherent-potential approximation. Spectral functions reveal electronic dispersion, topology, orbital character, and broadening (electron-lifetime effects) due to chemical disorder. Dissolution of electron cylinders occurs near x∼0.9 with a nonuniform, topological (Lifshitz) transition, reducing the interband interactions; yet the dispersion maintains its dxz or dyz character. Formation energies indicate alloying at x=0.35, as observed, and a tendency for segregation on the K-rich (x>0.6) side, explaining the difficulty of controlling sample quality and the conflicting results between characterized electronic structures. Our results reveal Fermi surface transitions in alloyed samples that influence s± to nodal superconductivity and suggest the origin for deviations of common trends in Fe-based superconductors, such as Bud'ko-Ni-Canfield scaling.
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Affiliation(s)
- Suffian N Khan
- Department of Physics, University of Illinois, Urbana-Champaign, Illinois 61801, USA and The Ames Laboratory, U.S. Department of Energy, Ames, Iowa 50011-3020, USA
| | - Duane D Johnson
- Department of Physics, University of Illinois, Urbana-Champaign, Illinois 61801, USA and The Ames Laboratory, U.S. Department of Energy, Ames, Iowa 50011-3020, USA and Department of Materials Science & Engineering, Iowa State University, Ames, Iowa 50011-2300, USA
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11
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Anisimov VI, Lukoyanov AV. Investigation of real materials with strong electronic correlations by the LDA+DMFT method. Acta Crystallogr C Struct Chem 2014; 70:137-59. [PMID: 24508959 DOI: 10.1107/s2053229613032312] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2013] [Accepted: 11/20/2013] [Indexed: 11/10/2022] Open
Abstract
Materials with strong electronic correlations are at the cutting edge of experimental and theoretical studies, capturing the attention of researchers for a great variety of interesting phenomena: metal-insulator, phase and magnetic spin transitions, `heavy fermion' systems, interplay between magnetic order and superconductivity, appearance and disappearance of local magnetic moments, and transport property anomalies. It is clear that the richness of physical phenomena for these compounds is a result of partially filled 3d, 4f or 5f electron shells with local magnetic moments preserved in the solid state. Strong interactions of d and f electrons with each other and with itinerant electronic states of the material are responsible for its anomalous properties. Electronic structure calculations for strongly correlated materials should explicitly take into account Coulombic interactions between d or f electrons. Recent advances in this field are related to the development of the LDA+DMFT method, which combines local density approximation (LDA) with dynamical mean-field theory (DMFT) to account for electronic correlation effects. In recent years, LDA+DMFT has allowed the successful treatment not only of simple systems but also of complicated real compounds. Nowadays, the LDA+DMFT method is the state-of-the-art tool for investigating correlated metals and insulators, spin and metal-insulator transitions (MIT) in transition-metal compounds in paramagnetic and magnetically ordered phases.
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Affiliation(s)
- V I Anisimov
- Institute of Metal Physics, Russian Academy of Sciences, 620990 Yekaterinburg, Russia
| | - A V Lukoyanov
- Institute of Metal Physics, Russian Academy of Sciences, 620990 Yekaterinburg, Russia
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12
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Anomalous surface lattice dynamics in the low-temperature phase of Ba(Fe1-xCox)2As2. Proc Natl Acad Sci U S A 2013; 110:898-903. [PMID: 23284168 DOI: 10.1073/pnas.1220170110] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
In complex materials, how correlation between charge, spin, and lattice affects the emergent phenomena remains unclear. The newly discovered iron-based high-temperature superconductors and related compounds present to the community a prototype family of materials, where interplay between charge, spin, and lattice degrees of freedom can be explored. With the occurrence of structural, magnetic, and superconducting transitions in the bulk of these materials, creating a surface will change the delicate balance between these phases, resulting in new behavior. A surface lattice dynamics study on (001) Ba(Fe(1-x)Co(x))(2)As(2), through electron energy loss spectroscopy measurements, reveals unusual temperature dependence of both the phonon frequency and line width in the low-temperature orthorhombic phase. The rate of change of phonon frequency with temperature is gigantic, two orders of magnitude larger than in the bulk. This behavior cannot be explained using conventional models of anharmonicity or electron-phonon coupling; instead, it requires that a large surface-spin-charge-lattice coupling be included. Furthermore, the higher surface-phase-transition temperature driven by surface stabilization of the low-temperature orthorhombic phase seems to turn the first-order transition (bulk) into the second-order type, equivalent to what is observed in the bulk by applying a uniaxial pressure. Such equivalence indicates that the surface mirrors the bulk under extreme conditions.
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Singh DJ. Superconductivity and magnetism in 11-structure iron chalcogenides in relation to the iron pnictides. SCIENCE AND TECHNOLOGY OF ADVANCED MATERIALS 2012; 13:054304. [PMID: 27877517 PMCID: PMC5099618 DOI: 10.1088/1468-6996/13/5/054304] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/29/2012] [Accepted: 10/29/2012] [Indexed: 06/03/2023]
Abstract
This is a review of the magnetism and superconductivity in '11'-type Fe chalcogenides, as compared to the Fe-pnictide materials. The chalcogenides show many differences from the pnictides, as might be anticipated from their very varied chemistries. These differences include stronger renormalizations that might imply stronger correlation effects as well as different magnetic ordering patterns. Nevertheless the superconducting state and mechanism for superconductivity are apparently similar for the two classes of materials. Unanswered questions and challenges to theory are emphasized.
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Affiliation(s)
- David Joseph Singh
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6056, USA
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14
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Thampy V, Kang J, Rodriguez-Rivera JA, Bao W, Savici AT, Hu J, Liu TJ, Qian B, Fobes D, Mao ZQ, Fu CB, Chen WC, Ye Q, Erwin RW, Gentile TR, Tesanovic Z, Broholm C. Friedel-like oscillations from interstitial iron in superconducting Fe(1+y)Te0.62Se0.38. PHYSICAL REVIEW LETTERS 2012; 108:107002. [PMID: 22463442 DOI: 10.1103/physrevlett.108.107002] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/23/2011] [Indexed: 05/31/2023]
Abstract
Using polarized and unpolarized neutron scattering, we show that interstitial Fe in superconducting Fe(1+y)Te(1-x)Se(x) induces a magnetic Friedel-like oscillation that diffracts at Q⊥=(1/2 0) and involves >50 neighboring Fe sites. The interstitial >2μ(B) moment is surrounded by compensating ferromagnetic four-spin clusters that may seed double stripe ordering in Fe(1+y)Te. A semimetallic five-band model with (1/2 1/2) Fermi surface nesting and fourfold symmetric superexchange between interstitial Fe and two in-plane nearest neighbors largely accounts for the observed diffraction.
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Affiliation(s)
- V Thampy
- Institute for Quantum Matter and Department of Physics and Astronomy, Johns Hopkins University, Baltimore, Maryland 21218, USA
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15
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Rettig L, Cortés R, Thirupathaiah S, Gegenwart P, Jeevan HS, Wolf M, Fink J, Bovensiepen U. Ultrafast momentum-dependent response of electrons in antiferromagnetic EuFe2As2 driven by optical excitation. PHYSICAL REVIEW LETTERS 2012; 108:097002. [PMID: 22463660 DOI: 10.1103/physrevlett.108.097002] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/17/2011] [Indexed: 05/31/2023]
Abstract
Employing the momentum sensitivity of time- and angle-resolved photoemission spectroscopy we demonstrate the analysis of ultrafast single- and many-particle dynamics in antiferromagnetic EuFe(2)As(2). Their separation is based on a temperature-dependent difference of photoexcited hole and electron relaxation times probing the single-particle band and the spin density wave gap, respectively. Reformation of the magnetic order occurs at 800 fs, which is 4 times slower compared to electron-phonon equilibration due to a smaller spin-dependent relaxation phase space.
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Affiliation(s)
- L Rettig
- Fachbereich Physik, Freie Universität Berlin, Arnimallee 14, D-14195 Berlin, Germany
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16
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Pandey A, Dhaka RS, Lamsal J, Lee Y, Anand VK, Kreyssig A, Heitmann TW, McQueeney RJ, Goldman AI, Harmon BN, Kaminski A, Johnston DC. Ba(1-x)K(x)Mn2As2: an antiferromagnetic local-moment metal. PHYSICAL REVIEW LETTERS 2012; 108:087005. [PMID: 22463561 DOI: 10.1103/physrevlett.108.087005] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/21/2011] [Indexed: 05/31/2023]
Abstract
The compound BaMn2As2 with the tetragonal ThCr2Si2 structure is a local-moment antiferromagnetic insulator with a Néel temperature T(N)=625 K and a large ordered moment μ=3.9μ(B)/Mn. We demonstrate that this compound can be driven metallic by partial substitution of Ba by K while retaining the same crystal and antiferromagnetic structures together with nearly the same high T(N) and large μ. Ba(1-x)K(x)Mn2As2 is thus the first metallic ThCr2Si2-type MAs-based system containing local 3d transition metal M magnetic moments, with consequences for the ongoing debate about the local-moment versus itinerant pictures of the FeAs-based superconductors and parent compounds. The Ba(1-x)K(x)Mn2As2 class of compounds also forms a bridge between the layered iron pnictides and cuprates and may be useful to test theories of high T(c) superconductivity.
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Affiliation(s)
- Abhishek Pandey
- Ames Laboratory and Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA.
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17
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Ding H, Nakayama K, Richard P, Souma S, Sato T, Takahashi T, Neupane M, Xu YM, Pan ZH, Fedorov AV, Wang Z, Dai X, Fang Z, Chen GF, Luo JL, Wang NL. Electronic structure of optimally doped pnictide Ba0.6K0.4Fe2As2: a comprehensive angle-resolved photoemission spectroscopy investigation. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2011; 23:135701. [PMID: 21415479 DOI: 10.1088/0953-8984/23/13/135701] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
The electronic structure of the Fe-based superconductor Ba(0.6)K(0.4)Fe(2)As(2) is studied by means of angle-resolved photoemission. We identify dispersive bands crossing the Fermi level forming hole-like (electron-like) Fermi surfaces (FSs) around Γ (M) with nearly nested FS pockets connected by the antiferromagnetic wavevector. Compared to band structure calculation findings, the overall bandwidth is reduced by a factor of 2 and the low energy dispersions display even stronger mass renormalization. Using an effective tight banding model, we fitted the band structure and the FSs to obtain band parameters reliable for theoretical modeling and calculation of physical quantities.
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Affiliation(s)
- H Ding
- Beijing National Laboratory for Condensed Matter Physics, Chinese Academy of Sciences, Beijing, People's Republic of China.
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18
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da Conceição CMS, Silva Neto MB, Marino EC. Magnetic and quasiparticle excitation spectra of an itinerant J1-J2 model for iron-pnictide superconductors. PHYSICAL REVIEW LETTERS 2011; 106:117002. [PMID: 21469890 DOI: 10.1103/physrevlett.106.117002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/29/2010] [Revised: 12/08/2010] [Indexed: 05/30/2023]
Abstract
We calculate the magnetic and quasiparticle excitation spectra of an itinerant J(1)-J(2) model for iron-pnictide superconductors. In addition to an acoustic spin-wave branch, the magnetic spectrum has a second, optical branch, resulting from the coupled four-sublattice magnetic structure. The spin-wave velocity has also a planar directional anisotropy, due to the collinear or striped antiferromagnetism. Within the magnetically ordered phase, the quasiparticle spectrum is composed of two Dirac cones, resulting from the folding of the magnetic Brillouin zone. We discuss the relevance of our findings to the understanding of both neutron scattering and photoemission spectroscopy results for SrFe(2)As(2).
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Affiliation(s)
- C M S da Conceição
- Departamento de Física Teórica, Universidade do Estado do Rio de Janeiro, Rio de Janeiro, RJ 20550-013, Brasil
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19
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Skornyakov SL, Katanin AA, Anisimov VI. Linear-temperature dependence of static magnetic susceptibility in LaFeAsO from dynamical mean-field theory. PHYSICAL REVIEW LETTERS 2011; 106:047007. [PMID: 21405353 DOI: 10.1103/physrevlett.106.047007] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/08/2010] [Indexed: 05/30/2023]
Abstract
In this Letter we report the local density approximation with dynamical mean field theory results for magnetic properties of the parent superconductor LaFeAsO in the paramagnetic phase. Calculated uniform magnetic susceptibility shows linear dependence at intermediate temperatures in agreement with experimental data. Contributions to the temperature dependence of the uniform susceptibility are strongly orbitally dependent. For high temperatures (>1000 K) susceptibility first saturates and then decreases with temperature. Our results demonstrate that linear-temperature dependence of static magnetic susceptibility in pnictide superconductors can be reproduced without invoking antiferromagnetic fluctuations.
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Affiliation(s)
- S L Skornyakov
- Institute of Metal Physics, Russian Academy of Sciences, Russia Ural Federal University, Yekaterinburg, Russia
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20
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Gao Y, Huang HX, Chen C, Ting CS, Su WP. Model of vortex states in hole-doped iron-pnictide superconductors. PHYSICAL REVIEW LETTERS 2011; 106:027004. [PMID: 21405248 DOI: 10.1103/physrevlett.106.027004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/24/2010] [Indexed: 05/30/2023]
Abstract
Based on a phenomenological model with competing spin-density-wave (SDW) and extended s-wave superconductivity, the vortex states in Ba(1-x)K(x)Fe2As2 are investigated by solving Bogoliubov-de Gennes equations. Our result for the optimally doped compound without induced SDW is in qualitative agreement with recent scanning tunneling microscopy experiment. We also propose that the main effect of the SDW on the vortex states is to reduce the intensity of the in-gap peak in the local density of states and transfer the spectral weight to form additional peaks outside the gap.
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Affiliation(s)
- Yi Gao
- Department of Physics and Texas Center for Superconductivity, University of Houston, Houston, Texas 77204, USA
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21
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Vorontsov AB, Vekhter I. Nodes versus minima in the energy gap of iron pnictide superconductors from field-induced anisotropy. PHYSICAL REVIEW LETTERS 2010; 105:187004. [PMID: 21231129 DOI: 10.1103/physrevlett.105.187004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/20/2010] [Indexed: 05/30/2023]
Abstract
We develop the formalism for computing the oscillations of the specific heat and thermal transport under rotated magnetic field in multiband superconductors with anisotropic gap and apply it to iron-based materials. We show that these oscillations change sign at low temperatures and fields, which strongly influences the experimental conclusions about the gap structure. We find that recent measurements of the specific heat oscillations indicate that the iron-based superconductors possess an anisotropic gap with deep minima or nodes close to the line connecting electron and hole pockets. We predict the behavior of the thermal conductivity that will help distinguish between these cases.
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Affiliation(s)
- A B Vorontsov
- Department of Physics, Montana State University, Bozeman, Montana 59717, USA
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22
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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. PHYSICAL REVIEW LETTERS 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] [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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23
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Chen ZG, Dong T, Ruan RH, Hu BF, Cheng B, Hu WZ, Zheng P, Fang Z, Dai X, Wang NL. Measurement of the c-axis optical reflectance of AFe2As2 (A=Ba, Sr) single crystals: evidence of different mechanisms for the formation of two energy gaps. PHYSICAL REVIEW LETTERS 2010; 105:097003. [PMID: 20868186 DOI: 10.1103/physrevlett.105.097003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/12/2010] [Revised: 06/21/2010] [Indexed: 05/29/2023]
Abstract
We present the c-axis optical reflectance measurement on single crystals of BaFe2As2 and SrFe2As2, the parent compounds of FeAs based superconductors. Different from the ab-plane optical response where two distinct energy gaps were observed in the spin-density-wave (SDW) state, only the smaller energy gap could be seen clearly for E∥c axis. The very pronounced energy gap structure seen at a higher energy scale for E∥ab plane is almost invisible. We propose a novel picture for the band structure evolution across the SDW transition and suggest different driving mechanisms for the formation of the two energy gaps.
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Affiliation(s)
- Z G Chen
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
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24
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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. PHYSICAL REVIEW LETTERS 2010; 105:087001. [PMID: 20868126 DOI: 10.1103/physrevlett.105.087001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [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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25
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Liu H, Chen GF, Zhang W, Zhao L, Liu G, Xia TL, Jia X, Mu D, Liu S, He S, Peng Y, He J, Chen Z, Dong X, Zhang J, Wang G, Zhu Y, Xu Z, Chen C, Zhou XJ. Unusual electronic structure and observation of dispersion kink in CeFeAsO parent compound of FeAs-based superconductors. PHYSICAL REVIEW LETTERS 2010; 105:027001. [PMID: 20867728 DOI: 10.1103/physrevlett.105.027001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/15/2009] [Indexed: 05/29/2023]
Abstract
We report the first comprehensive high-resolution angle-resolved photoemission measurements on CeFeAsO, a parent compound of FeAs-based high temperature superconductors with a magnetic-structural transition at ∼150 K. In the magnetic-ordering state, four holelike Fermi surface sheets are observed near Γ(0,0), and the Fermi surface near M(±π,±π) shows a tiny electronlike pocket at M surrounded by four strong spots. The unusual Fermi surface topology deviates strongly from the band structure calculations. The electronic signature of the magnetic-structural transition shows up in the dramatic change of the quasiparticle scattering rate. A dispersion kink at ∼25 meV is observed for the first time in the parent compound of Fe-based superconductors.
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Affiliation(s)
- Haiyun Liu
- National Lab for Superconductivity, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
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26
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Knolle J, Eremin I, Akbari A, Moessner R. Quasiparticle interference in the spin-density wave phase of iron-based superconductors. PHYSICAL REVIEW LETTERS 2010; 104:257001. [PMID: 20867410 DOI: 10.1103/physrevlett.104.257001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/12/2010] [Indexed: 05/29/2023]
Abstract
We propose an explanation for the electronic nematic state observed recently in parent iron-based superconductors [T.-M. Chuang, Science 327, 181 (2010)10.1126/science.1181083]. We argue that the quasi-one-dimensional nanostructure identified in the quasiparticle interference (QPI) is a consequence of the interplay of the magnetic (π, 0) spin-density wave (SDW) order with the underlying electronic structure. We show that the evolution of the QPI peaks largely reflects quasiparticle scattering between bands involved in the SDW formation. Because of the ellipticity of the electron pocket and the fact that only one of the electron pockets is involved in the SDW, the resulting QPI has a pronounced one-dimensional structure. We further predict that the QPI crosses over to two dimensionality on an energy scale, set by the SDW gap.
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Affiliation(s)
- J Knolle
- Max Planck Institute for the Physics of Complex Systems, D-01187 Dresden, Germany
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27
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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. PHYSICAL REVIEW LETTERS 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] [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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28
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Richard P, Nakayama K, Sato T, Neupane M, Xu YM, Bowen JH, Chen GF, Luo JL, Wang NL, Dai X, Fang Z, Ding H, Takahashi T. Observation of Dirac cone electronic dispersion in BaFe2As2. PHYSICAL REVIEW LETTERS 2010; 104:137001. [PMID: 20481905 DOI: 10.1103/physrevlett.104.137001] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/03/2009] [Revised: 12/17/2009] [Indexed: 05/29/2023]
Abstract
We performed an angle-resolved photoemission spectroscopy study of BaFe2As2, which is the parent compound of the so-called 122 phase of the iron-pnictide high-temperature superconductors. We reveal the existence of a Dirac cone in the electronic structure of this material below the spin-density-wave temperature, which is responsible for small spots of high photoemission intensity at the Fermi level. Our analysis suggests that the cone is slightly anisotropic and its apex is located very near the Fermi level, leading to tiny Fermi surface pockets. The bands forming the cone show an anisotropic leading edge gap away from the cone that suggests a nodal spin-density-wave description.
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Affiliation(s)
- P Richard
- WPI Research Center, Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan.
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29
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Shimojima T, Ishizaka K, Ishida Y, Katayama N, Ohgushi K, Kiss T, Okawa M, Togashi T, Wang XY, Chen CT, Watanabe S, Kadota R, Oguchi T, Chainani A, Shin S. Orbital-dependent modifications of electronic structure across the magnetostructural transition in BaFe2As2. PHYSICAL REVIEW LETTERS 2010; 104:057002. [PMID: 20366786 DOI: 10.1103/physrevlett.104.057002] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/13/2009] [Indexed: 05/29/2023]
Abstract
Laser angle-resolved photoemission spectroscopy (ARPES) is employed to investigate the temperature (T) dependence of the electronic structure in BaFe2As2 across the magnetostructural transition at T{N} approximately 140 K. A drastic transformation in Fermi surface (FS) shape across T{N} is observed, as expected by first-principles band calculations. Polarization-dependent ARPES and band calculations consistently indicate that the observed FSs at k{z} approximately pi in the low-T antiferromagnetic state are dominated by the Fe3d{zx} orbital, leading to the twofold electronic structure. These results indicate that magnetostructural transition in BaFe2As2 accompanies orbital-dependent modifications in the electronic structure.
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Affiliation(s)
- T Shimojima
- Institute for Solid State Physics (ISSP), University of Tokyo, Kashiwa, Chiba 277-8581, Japan.
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30
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Zhang D. Nonmagnetic impurity resonances as a signature of sign-reversal pairing in FeAs-based superconductors. PHYSICAL REVIEW LETTERS 2009; 103:186402. [PMID: 19905818 DOI: 10.1103/physrevlett.103.186402] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/25/2009] [Indexed: 05/28/2023]
Abstract
The energy band structure of FeAs-based superconductors is fitted by a tight-binding model with two Fe ions per unit cell and two degenerate orbitals per Fe ion. Based on this, superconductivity with extended s-wave pairing symmetry of the form cosk(x)+cosk(y) is examined. The local density of states near an impurity is also investigated by using the T-matrix approach. For the nonmagnetic scattering potential, we found that there exist two major resonances inside the gap. The height of the resonance peaks depends on the strength of the impurity potential. These in-gap resonances are originated in the Andreev's bound states due to the quasiparticle scattering between the hole Fermi surfaces around Gamma point with positive order parameter and the electron Fermi surfaces around M point with negative order parameter.
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Affiliation(s)
- Degang Zhang
- Texas Center for Superconductivity and Department of Physics, University of Houston, Houston, Texas 77204, USA
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31
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Sato T, Nakayama K, Sekiba Y, Richard P, Xu YM, Souma S, Takahashi T, Chen GF, Luo JL, Wang NL, Ding H. Band structure and fermi surface of an extremely overdoped iron-based superconductor KFe2As2. PHYSICAL REVIEW LETTERS 2009; 103:047002. [PMID: 19659391 DOI: 10.1103/physrevlett.103.047002] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/03/2008] [Indexed: 05/28/2023]
Abstract
We have performed high-resolution angle-resolved photoemission spectroscopy on heavily overdoped KFe_{2}As_{2} (transition temperature T_{c} = 3 K). We observed several renormalized bands near the Fermi level with a renormalization factor of 2-4. While the Fermi surface around the Brillouin-zone center is qualitatively similar to that of optimally doped Ba_{1-x}K_{x}Fe_{2}As_{2} (x = 0.4; T_{c} = 37 K), the Fermi surface topology around the zone corner (M point) is markedly different: the two electron Fermi surface pockets are completely absent due to an excess of hole doping. This result indicates that the electronic states around the M point play an important role in the high-T_{c} superconductivity of Ba_{1-x}K_{x}Fe_{2}As_{2} and suggests that the interband scattering via the antiferromagnetic wave vector essentially controls the T_{c} value in the overdoped region.
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Affiliation(s)
- T Sato
- Department of Physics, Tohoku University, Sendai 980-8578, Japan and TRiP, Japan Science and Technology Agency (JST), Kawaguchi 332-0012, Japan
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32
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Lu F, Zou LJ. Superconducting pairing symmetry and energy gaps of the two-orbital t-t'-J-J' model: comparisons with the ARPES experiments in iron pnictides. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2009; 21:255701. [PMID: 21828440 DOI: 10.1088/0953-8984/21/25/255701] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Motivated by the discovery of the iron-based superconductors, we present the theoretical results on the superconducting phase diagram, the temperature-dependent Fermi surface structures in normal state and the angle-resolved photoemission spectroscopy (ARPES) character of quasiparticles of the two-orbital t-t'-J-J' model. In the reasonable physical parameter region of LaFeAsO(1-x)F(x), we find the superconducting phase is stable, and the pairing symmetry is weakly anisotropic and nodeless d(x(2)-ηy(2))+S(x(2)y(2))-wave, qualitatively in agreement with the ARPES experiments in iron pnictide superconductors. Nevertheless, the two ratios of the energy gaps to T(c) deviate from the ARPES data, suggesting that a more elaborate theoretical model is needed.
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Affiliation(s)
- Feng Lu
- Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, PO Box 1129, Hefei 230031, People's Republic of China. Graduate School of the Chinese Academy of Sciences, Beijing 100049, People's Republic of China
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33
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Korshunov MM, Eremin I, Efremov DV, Maslov DL, Chubukov AV. Nonanalytic spin susceptibility of a Fermi liquid: the case of Fe-based pnictides. PHYSICAL REVIEW LETTERS 2009; 102:236403. [PMID: 19658954 DOI: 10.1103/physrevlett.102.236403] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/30/2008] [Indexed: 05/28/2023]
Abstract
We propose an explanation of the peculiar linear temperature dependence of the uniform spin susceptibility chi(T) in ferropnictides. We argue that the linear in T term appears to be due to the nonanalytic temperature dependence of chi(T) in a two-dimensional Fermi liquid. We show that the prefactor of the T term is expressed via the square of the spin-density-wave (SDW) amplitude connecting nested hole and electron pockets. Because of an incipient SDW instability, this amplitude is large, which, along with a small value of the Fermi energy, makes the T dependence of chi(T) strong. We demonstrate that this mechanism is in quantitative agreement with the experiment.
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Affiliation(s)
- M M Korshunov
- Max-Planck-Institut für Physik komplexer Systeme, D-01187 Dresden, Germany.
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34
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Yang J, Hüvonen D, Nagel U, Rõõm T, Ni N, Canfield PC, Bud'ko SL, Carbotte JP, Timusk T. Optical spectroscopy of superconducting Ba0.55K0.45Fe2As2: evidence for strong coupling to low-energy bosons. PHYSICAL REVIEW LETTERS 2009; 102:187003. [PMID: 19518902 DOI: 10.1103/physrevlett.102.187003] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/07/2008] [Indexed: 05/27/2023]
Abstract
Normal state optical spectroscopy on single crystals of the new iron arsenide superconductor Ba0.55K0.45Fe2As2 shows that the infrared spectrum consists of two major components: a strong metallic Drude band and a well-separated midinfrared absorption centered at 0.7 eV. It is difficult to separate the two components unambiguously but several fits using Lorentzian peaks suggest a model with a Drude peak having a plasma frequency of 1.6 to 2.1 eV and a midinfrared peak with a plasma frequency of 2.5 eV. Detailed analysis of the frequency dependent scattering rate shows that the charge carriers interact with a broad bosonic spectrum extending beyond 100 meV with a very large coupling constant lambda=3.4 at low temperature. As the temperature increases this coupling weakens to lambda=0.78 at ambient temperature. This suggests a bosonic spectrum that is similar to what is seen in the lower Tc cuprates.
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Affiliation(s)
- J Yang
- Department of Physics and Astronomy, McMaster University, Hamilton, Ontario L8S 4M1, Canada
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35
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Terashima K, Sekiba Y, Bowen JH, Nakayama K, Kawahara T, Sato T, Richard P, Xu YM, Li LJ, Cao GH, Xu ZA, Ding H, Takahashi T. Fermi surface nesting induced strong pairing in iron-based superconductors. Proc Natl Acad Sci U S A 2009; 106:7330-3. [PMID: 19359490 PMCID: PMC2667370 DOI: 10.1073/pnas.0900469106] [Citation(s) in RCA: 302] [Impact Index Per Article: 20.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2009] [Indexed: 11/18/2022] Open
Abstract
The discovery of high-temperature superconductivity in iron pnictides raised the possibility of an unconventional superconducting mechanism in multiband materials. The observation of Fermi-surface (FS)-dependent nodeless superconducting gaps suggested that inter-FS interactions may play a crucial role in superconducting pairing. In the optimally hole-doped Ba(0.6)K(0.4)Fe(2)As(2), the pairing strength is enhanced simultaneously (2Delta/T(c) approximately 7) on the nearly nested FS pockets, i.e., the inner hole-like (alpha) FS and the 2 hybridized electron-like FSs, whereas the pairing remains weak (2Delta/T(c) approximately 3.6) in the poorly nested outer hole-like (beta) FS. Here, we report that in the electron-doped BaFe(1.85)Co(0.15)As(2), the FS nesting condition switches from the alpha to the beta FS due to the opposite size changes for hole- and electron-like FSs upon electron doping. The strong pairing strength (2Delta/T(c) approximately 6) is also found to switch to the nested beta FS, indicating an intimate connection between FS nesting and superconducting pairing, and strongly supporting the inter-FS pairing mechanism in the iron-based superconductors.
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Affiliation(s)
- K Terashima
- Ultraviolet Synchrotron Orbital Radiation Facility, Institute for Molecular Science, Okazaki 444-8585, Japan.
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36
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Liu C, Kondo T, Ni N, Palczewski AD, Bostwick A, Samolyuk GD, Khasanov R, Shi M, Rotenberg E, Bud'ko SL, Canfield PC, Kaminski A. Three- to two-dimensional transition of the electronic structure in CaFe2As2: a parent compound for an iron arsenic high-temperature superconductor. PHYSICAL REVIEW LETTERS 2009; 102:167004. [PMID: 19518747 DOI: 10.1103/physrevlett.102.167004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/21/2009] [Indexed: 05/27/2023]
Abstract
We use angle-resolved photoemission spectroscopy (ARPES) to study the electronic properties of CaFe2As2-parent compound of a pnictide superconductor. We find that the structural and magnetic transition is accompanied by a three- to two-dimensional (3D-2D) crossover in the electronic structure. Above the transition temperature (T_{s}) Fermi surfaces around Gamma and X points are cylindrical and quasi 2D. Below T_{s}, the Gamma pocket forms a 3D ellipsoid, while the X pocket remains quasi 2D. This finding strongly suggests that low dimensionality plays an important role in understanding the superconducting mechanism in pnictides.
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Affiliation(s)
- Chang Liu
- Ames Laboratory and Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA
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37
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Zhang Y, Wei J, Ou HW, Zhao JF, Zhou B, Chen F, Xu M, He C, Wu G, Chen H, Arita M, Shimada K, Namatame H, Taniguchi M, Chen XH, Feng DL. Unusual doping dependence of the electronic structure and coexistence of spin-density-wave and superconductor phases in single crystalline Sr1-xKxFe2As2. PHYSICAL REVIEW LETTERS 2009; 102:127003. [PMID: 19392313 DOI: 10.1103/physrevlett.102.127003] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/24/2008] [Indexed: 05/27/2023]
Abstract
The nature of the spin-density wave (SDW) and its relation with superconductivity are crucial issues in the newly discovered iron-pnictide superconductors. Particularly, it is unclear whether the superconducting phase and SDW are truly exclusive from each other. We here report splittings of the band structures in Sr1-xKxFe2As2 (x=0, 0.1, 0.18), and their unusual doping dependence. Our data on single crystalline samples prove that the SDW and superconductivity could coexist in iron pnictides.
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Affiliation(s)
- Y Zhang
- Department of Physics, Surface Physics Laboratory, Fudan University, Shanghai 200433, People's Republic of China
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38
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Baily SA, Kohama Y, Hiramatsu H, Maiorov B, Balakirev FF, Hirano M, Hosono H. Pseudoisotropic upper critical field in cobalt-doped SrFe2As2 epitaxial films. PHYSICAL REVIEW LETTERS 2009; 102:117004. [PMID: 19392231 DOI: 10.1103/physrevlett.102.117004] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/14/2008] [Indexed: 05/15/2023]
Abstract
We present resistivity measurements of the complete superconducting upper critical field (H{c2}) phase diagram as a function of angle (theta) and temperature (T) for cobalt-doped SrFe2As2 epitaxial films to 0.5 K and 50 T. Although H{c2}(theta) at 10 K is indistinguishable from that derived from a single-band anisotropy model, the apparent anisotropy H{c2}{ perpendicularc}/H{c2};{ parallelc} linearly decreases to 1 at low T, with H{c2}(0)=47 T. The data are well described by a two-band model with small, opposing anisotropies for the bands. This unusual relationship is confirmed by the observation of a local maximum for H{c2};{ parallelc} at low T.
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Affiliation(s)
- S A Baily
- National High Magnetic Field Laboratory, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.
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Zabolotnyy VB, Inosov DS, Evtushinsky DV, Koitzsch A, Kordyuk AA, Sun GL, Park JT, Haug D, Hinkov V, Boris AV, Lin CT, Knupfer M, Yaresko AN, Büchner B, Varykhalov A, Follath R, Borisenko SV. (pi, pi) electronic order in iron arsenide superconductors. Nature 2009; 457:569-72. [PMID: 19177126 DOI: 10.1038/nature07714] [Citation(s) in RCA: 177] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2008] [Accepted: 12/02/2008] [Indexed: 11/09/2022]
Abstract
The distribution of valence electrons in metals usually follows the symmetry of the underlying ionic lattice. Modulations of this distribution often occur when those electrons are not stable with respect to a new electronic order, such as spin or charge density waves. Electron density waves have been observed in many families of superconductors, and are often considered to be essential for superconductivity to exist. Recent measurements seem to show that the properties of the iron pnictides are in good agreement with band structure calculations that do not include additional ordering, implying no relation between density waves and superconductivity in these materials. Here we report that the electronic structure of Ba(1-x)K(x)Fe(2)As(2) is in sharp disagreement with those band structure calculations, and instead reveals a reconstruction characterized by a (pi, pi) wavevector. This electronic order coexists with superconductivity and persists up to room temperature (300 K).
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Affiliation(s)
- V B Zabolotnyy
- Institute for Solid State Research, IFW-Dresden, PO Box 270116, 01171 Dresden, Germany
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40
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Richard P, Sato T, Nakayama K, Souma S, Takahashi T, Xu YM, Chen GF, Luo JL, Wang NL, Ding H. Angle-resolved photoemission spectroscopy of the Fe-Based Ba0.6K0.4Fe2As2 high temperature superconductor: evidence for an orbital selective electron-mode coupling. PHYSICAL REVIEW LETTERS 2009; 102:047003. [PMID: 19257465 DOI: 10.1103/physrevlett.102.047003] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/14/2008] [Indexed: 05/27/2023]
Abstract
We have performed an angle-resolved photoemission spectroscopy study of the new superconductor Ba0.6K0.4Fe2As2 in the low energy range. We report the observation of an anomaly around 25 meV in the dispersion of superconducting Ba0.6K0.4Fe2As2 samples that nearly vanishes above T_{c}. The energy scale of the related mode (13+/-2 meV) and its strong dependence on orbital and temperature indicates that it is unlikely related to phonons. Moreover, the momentum locations of the kink can be connected by the antiferromagnetic wave vector. Our results point towards an unconventional electronic origin of the mode and the superconducting pairing in the Fe-based superconductors, and strongly support the antiphase s-wave pairing symmetry.
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Affiliation(s)
- P Richard
- WPI Research Center, Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan.
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Yuan HQ, Singleton J, Balakirev FF, Baily SA, Chen GF, Luo JL, Wang NL. Nearly isotropic superconductivity in (Ba,K)Fe2As2. Nature 2009; 457:565-8. [DOI: 10.1038/nature07676] [Citation(s) in RCA: 444] [Impact Index Per Article: 29.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2008] [Accepted: 11/24/2008] [Indexed: 11/09/2022]
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Hu WZ, Dong J, Li G, Li Z, Zheng P, Chen GF, Luo JL, Wang NL. Origin of the spin density wave instability in AFe2As2 (A=Ba,Sr) as revealed by optical spectroscopy. PHYSICAL REVIEW LETTERS 2008; 101:257005. [PMID: 19113746 DOI: 10.1103/physrevlett.101.257005] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/17/2008] [Revised: 08/05/2008] [Indexed: 05/27/2023]
Abstract
We performed optical spectroscopy measurement on single crystals of BaFe2As2 and SrFe2As2, the parent compounds of FeAs-based superconductors. Both are found to be quite metallic with fairly large plasma frequencies at high temperature. Upon entering the spin-density-wave state, the formation of partial energy gaps was clearly observed with the surprising presence of two different energy scales. A large part of the Drude component was removed by the gapping of Fermi surfaces. Meanwhile, the carrier scattering rate was even more dramatically reduced. We elaborate that the spin-density-wave instability is more likely to be driven by the Fermi surface nesting of itinerant electrons than a local-exchange mechanism.
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Affiliation(s)
- W Z Hu
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
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Christianson AD, Goremychkin EA, Osborn R, Rosenkranz S, Lumsden MD, Malliakas CD, Todorov IS, Claus H, Chung DY, Kanatzidis MG, Bewley RI, Guidi T. Unconventional superconductivity in Ba0.6K0.4Fe2As2 from inelastic neutron scattering. Nature 2008; 456:930-2. [DOI: 10.1038/nature07625] [Citation(s) in RCA: 521] [Impact Index Per Article: 32.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2008] [Accepted: 10/29/2008] [Indexed: 11/09/2022]
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