Specific heat and thermal conductivity in the vortex state of the two-gap superconductor MgB2

Abstract

The specific-heat coefficient γs(H) and the electronic thermal conductivity κes(H) are calculated for Abrikosov’s vortex lattice by taking into account the effects of supercurrent flow and Andreev scattering. First we solve the gap equation for the entire range of magnetic fields. We take into account vertex corrections due to impurity scattering calculated in the Born approximation. The function γs(H)/γn increases from zero and becomes approximately linear above H/Hc2∼0.1. The dependence on impurity scattering is substantially reduced by the vertex corrections. The upward curvature of κes(H)/κen, which is caused by decreasing Andreev scattering for increasing field, is reduced for increasing impurity scattering. We also calculate the temperature dependence of the scattering rates 1/τps(H) of a phonon and 1/τes(H) of a quasiparticle due to quasiparticle and phonon scattering, respectively. At low temperatures the ratio τpn/τps(H) increases rapidly to one as H tends to Hc2 which yields a rapid drop in the phononic thermal conductivity κph. Our results are in qualitative agreement with the experiments on the two-gap superconductor MgB2.

Source-reported materials — not catalogue approval

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