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Title: Superconductivity and fluctuations in Ba 1–pK pFe 2As 2 and Ba(Fe 1–nCo n) 2As 2

Abstract

In this paper, we study the interplay of fluctuations and superconductivity in BaFe 2As 2 (Ba-122) compounds with Ba and Fe substituted by K (p doping) and Co (n doping), respectively. To this end, we measured electronic Raman spectra as a function of polarization and temperature. We observe gap excitations and fluctuations for all doping levels studied. The response from fluctuations is much stronger for Co substitution and, according to the selection rules and the temperature dependence, originates from the exchange of two critical spin fluctuations with characteristic wave vectors (±π,0) and (0,±π). At 22% K doping (p = 0.22), we find the same selection rules and spectral shape for the fluctuations but the intensity is smaller by a factor of 5. Since there exists no nematic region above the orthorhombic spin-density-wave (SDW) phase, the identification of the fluctuations via the temperature dependence is not possible. The gap excitations in the superconducting state indicate strongly anisotropic near-nodal gaps for Co substitution which make the observation of collective modes difficult. The variation with doping of the spectral weights of the A 1g and B 1g gap features does not support the influence of fluctuations on Cooper pairing. Thus, the observation ofmore » Bardasis–Schrieffer modes inside the nearly clean gaps on the K-doped side remains the only experimental evidence for the relevance of fluctuations for pairing.« less

Authors:
 [1];  [2];  [2];  [2];  [2];  [2];  [3];  [3];  [4];  [5];  [5];  [6]
  1. Bavarian Academy of Sciences and Humanities, Garching (Germany). Walther Meissner Inst.; Technical Univ. of Munich, Garching (Germany). Faculty of Physics; SLAC National Accelerator Lab., Menlo Park, CA (United States). Stanford Inst. for Materials and Energy Sciences (SIMES)
  2. Bavarian Academy of Sciences and Humanities, Garching (Germany). Walther Meissner Inst.; Technical Univ. of Munich, Garching (Germany). Faculty of Physics
  3. Karlsruhe Inst. of Technology (KIT) (Germany). Inst. of Solid State Physics
  4. Nanjing Univ. (China). Dept. of Physics. National Lab. of Solid State Microstructures
  5. SLAC National Accelerator Lab., Menlo Park, CA (United States). Stanford Inst. for Materials and Energy Sciences (SIMES); Stanford Univ., CA (United States). Geballe Lab. for Advanced Materials. Dept. of Applied Physics
  6. Bavarian Academy of Sciences and Humanities, Garching (Germany). Walther Meissner Inst.
Publication Date:
Research Org.:
SLAC National Accelerator Lab., Menlo Park, CA (United States); Stanford Univ., CA (United States); Bavarian Academy of Sciences and Humanities, Garching (Germany); Technical Univ. of Munich, Garching (Germany)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); German Research Foundation (DFG); Transregional Collaborative Research Center (Germany)
OSTI Identifier:
1349070
Grant/Contract Number:
AC02-76SF00515; HA 2071/7; A5 [2012-2]; TRR 80
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Physica Status Solidi B. Basic Solid State Physics
Additional Journal Information:
Journal Volume: 254; Journal Issue: 1; Journal ID: ISSN 0370-1972
Publisher:
Wiley-Blackwell
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; BaFe2As2; doping; fluctuations; light scattering; magnetism; superconductivity

Citation Formats

Böhm, T., Hosseinian Ahangharnejhad, R., Jost, D., Baum, A., Muschler, B., Kretzschmar, F., Adelmann, P., Wolf, T., Wen, H. -H., Chu, J. -H., Fisher, I. R., and Hackl, R.. Superconductivity and fluctuations in Ba1–pKpFe2As2 and Ba(Fe1–nCon)2As2. United States: N. p., 2016. Web. doi:10.1002/pssb.201600308.
Böhm, T., Hosseinian Ahangharnejhad, R., Jost, D., Baum, A., Muschler, B., Kretzschmar, F., Adelmann, P., Wolf, T., Wen, H. -H., Chu, J. -H., Fisher, I. R., & Hackl, R.. Superconductivity and fluctuations in Ba1–pKpFe2As2 and Ba(Fe1–nCon)2As2. United States. doi:10.1002/pssb.201600308.
Böhm, T., Hosseinian Ahangharnejhad, R., Jost, D., Baum, A., Muschler, B., Kretzschmar, F., Adelmann, P., Wolf, T., Wen, H. -H., Chu, J. -H., Fisher, I. R., and Hackl, R.. 2016. "Superconductivity and fluctuations in Ba1–pKpFe2As2 and Ba(Fe1–nCon)2As2". United States. doi:10.1002/pssb.201600308. https://www.osti.gov/servlets/purl/1349070.
@article{osti_1349070,
title = {Superconductivity and fluctuations in Ba1–pKpFe2As2 and Ba(Fe1–nCon)2As2},
author = {Böhm, T. and Hosseinian Ahangharnejhad, R. and Jost, D. and Baum, A. and Muschler, B. and Kretzschmar, F. and Adelmann, P. and Wolf, T. and Wen, H. -H. and Chu, J. -H. and Fisher, I. R. and Hackl, R.},
abstractNote = {In this paper, we study the interplay of fluctuations and superconductivity in BaFe2As2 (Ba-122) compounds with Ba and Fe substituted by K (p doping) and Co (n doping), respectively. To this end, we measured electronic Raman spectra as a function of polarization and temperature. We observe gap excitations and fluctuations for all doping levels studied. The response from fluctuations is much stronger for Co substitution and, according to the selection rules and the temperature dependence, originates from the exchange of two critical spin fluctuations with characteristic wave vectors (±π,0) and (0,±π). At 22% K doping (p = 0.22), we find the same selection rules and spectral shape for the fluctuations but the intensity is smaller by a factor of 5. Since there exists no nematic region above the orthorhombic spin-density-wave (SDW) phase, the identification of the fluctuations via the temperature dependence is not possible. The gap excitations in the superconducting state indicate strongly anisotropic near-nodal gaps for Co substitution which make the observation of collective modes difficult. The variation with doping of the spectral weights of the A1g and B1g gap features does not support the influence of fluctuations on Cooper pairing. Thus, the observation of Bardasis–Schrieffer modes inside the nearly clean gaps on the K-doped side remains the only experimental evidence for the relevance of fluctuations for pairing.},
doi = {10.1002/pssb.201600308},
journal = {Physica Status Solidi B. Basic Solid State Physics},
number = 1,
volume = 254,
place = {United States},
year = 2016,
month = 8
}

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