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Title: Specific Heat of Ba 0.59K 0.41Fe 2As 2, an Fe-Pnictide Superconductor with T c = 36.9 K, and a New Method for Identifying the Electron Contribution [Specific Heat of Ba 0.59K 0.41Fe 2As 2, and a New Method for Identifying the Electron Contribution: Two Electron Bands with Different Energy Gaps in the Superconducting State]

Abstract

Here, we report specific-heat measurements on Ba 0.59K 0.41Fe 2As 2, one of a family of high-T cFe-pnictide superconductors for which the pairing interaction is of special interest. We use a new method, based on direct comparisons of α-model expressions for the electron contribution with the measured total specific heat, to extract the electron contribution. It circumvents the need in the conventional analyses for an independent, necessarily approximate, determination of the lattice contribution, which is subtracted from the total to obtain the electron contribution, and it eliminates the consequent uncertainties in the electron contribution. For Ba 0.59K 0.41Fe 2As 2 the electron density of states is comprised of contributions from two electron bands with superconducting-state energy gaps differing by a factor 3.8, with 77% coming from the band with the larger gap. The vortex-state specific heat suggests nodeless gaps. Comparison of the normal-state density of states with band-structure calculations shows an extraordinarily large effective mass enhancement, for which there is no precedent in simple metals and no theoretical explanation.

Authors:
 [1];  [2];  [3];  [3]
  1. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); UCLA, Los Angeles, CA (United States)
  2. Univ. of California, Berkeley, CA (United States); European Synchrotron Radiation Facility, Grenoble Cedex (France)
  3. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Univ. of California, Berkeley, CA (United States)
Publication Date:
Research Org.:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1466691
Grant/Contract Number:  
AC02-05CH11231
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Journal of the Physical Society of Japan
Additional Journal Information:
Journal Volume: 84; Journal Issue: 11; Related Information: Copyright © 2015 The Physical Society of Japan.; Journal ID: ISSN 0031-9015
Publisher:
Physical Society of Japan
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY

Citation Formats

Rotundu, Costel R., Forrest, Thomas R., Phillips, Norman E., and Birgeneau, Robert J. Specific Heat of Ba0.59K0.41Fe2As2, an Fe-Pnictide Superconductor with Tc = 36.9 K, and a New Method for Identifying the Electron Contribution [Specific Heat of Ba0.59K0.41Fe2As2, and a New Method for Identifying the Electron Contribution: Two Electron Bands with Different Energy Gaps in the Superconducting State]. United States: N. p., 2015. Web. doi:10.7566/JPSJ.84.114701.
Rotundu, Costel R., Forrest, Thomas R., Phillips, Norman E., & Birgeneau, Robert J. Specific Heat of Ba0.59K0.41Fe2As2, an Fe-Pnictide Superconductor with Tc = 36.9 K, and a New Method for Identifying the Electron Contribution [Specific Heat of Ba0.59K0.41Fe2As2, and a New Method for Identifying the Electron Contribution: Two Electron Bands with Different Energy Gaps in the Superconducting State]. United States. doi:10.7566/JPSJ.84.114701.
Rotundu, Costel R., Forrest, Thomas R., Phillips, Norman E., and Birgeneau, Robert J. Thu . "Specific Heat of Ba0.59K0.41Fe2As2, an Fe-Pnictide Superconductor with Tc = 36.9 K, and a New Method for Identifying the Electron Contribution [Specific Heat of Ba0.59K0.41Fe2As2, and a New Method for Identifying the Electron Contribution: Two Electron Bands with Different Energy Gaps in the Superconducting State]". United States. doi:10.7566/JPSJ.84.114701. https://www.osti.gov/servlets/purl/1466691.
@article{osti_1466691,
title = {Specific Heat of Ba0.59K0.41Fe2As2, an Fe-Pnictide Superconductor with Tc = 36.9 K, and a New Method for Identifying the Electron Contribution [Specific Heat of Ba0.59K0.41Fe2As2, and a New Method for Identifying the Electron Contribution: Two Electron Bands with Different Energy Gaps in the Superconducting State]},
author = {Rotundu, Costel R. and Forrest, Thomas R. and Phillips, Norman E. and Birgeneau, Robert J.},
abstractNote = {Here, we report specific-heat measurements on Ba0.59K0.41Fe2As2, one of a family of high-TcFe-pnictide superconductors for which the pairing interaction is of special interest. We use a new method, based on direct comparisons of α-model expressions for the electron contribution with the measured total specific heat, to extract the electron contribution. It circumvents the need in the conventional analyses for an independent, necessarily approximate, determination of the lattice contribution, which is subtracted from the total to obtain the electron contribution, and it eliminates the consequent uncertainties in the electron contribution. For Ba0.59K0.41Fe2As2 the electron density of states is comprised of contributions from two electron bands with superconducting-state energy gaps differing by a factor 3.8, with 77% coming from the band with the larger gap. The vortex-state specific heat suggests nodeless gaps. Comparison of the normal-state density of states with band-structure calculations shows an extraordinarily large effective mass enhancement, for which there is no precedent in simple metals and no theoretical explanation.},
doi = {10.7566/JPSJ.84.114701},
journal = {Journal of the Physical Society of Japan},
issn = {0031-9015},
number = 11,
volume = 84,
place = {United States},
year = {2015},
month = {10}
}

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