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Costel R. Rotundu, Thomas R. Forrest, Norman E. Phillips, and Robert J. Birgeneau. Specific heat of Ba0. 59K0. 45Fe2As2, and a new method for identifying the electron contribution: two electron bands with different energy gaps in the superconducting state. Journal of the Physical Society of Japan, 84, p. 114701, 2015.

Abstract: We report specific-heat measurements on Ba0.59K0.41Fe2As2, one of a family of high-Tc Fe-pnictide superconductors
for which the pairing interaction is of special interest. We use a new method, based on direct comparisons of alfa-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.

Keywords: heat capacity, superconductivity, K-doped BaFe2As2


Posted by Costel R Rotundu


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