Specific heat in strongly hole-doped Iron-based superconductors

Dmitry V. Chichinadze; Andrey V. Chubukov

doi:10.1103/PhysRevB.99.024509

paper

Specific heat in strongly hole-doped Iron-based superconductors

arXiv:1808.06224 · doi:10.1103/PhysRevB.99.024509

Abstract

We compute the specific heat $C (T)$ in an Fe-based superconductor with only hole pockets. We use a three-orbital/three pocket model with two smaller hole pockets made out of $d_{x z}$ and $d_{y z}$ orbitals and a larger pocket made out of $d_{x y}$ orbital. We use as an input the experimental fact that the mass of $d_{x y}$ fermion is much heavier than that of $d_{x z} / d_{y z}$ fermions. We argue that the heavy $d_{x y}$ band contributes most to the specific heat in the normal state, but the superconducting gap on the $d_{x y}$ pocket is parametrically smaller than that on $d_{x z} / d_{y z}$ pockets. We argue that in this situation the jump of $C (T)$ at $T_{c}$ is determined by $d_{x z} / d_{y z}$ fermions, and the ratio $(C_{s} - C_{n}) / C_{n}$ is a fraction of that in a one-band BCS theory. Below $T_{c}$ , $C (T)$ remains relatively flat down to some $T^{*}$ , below which $C (T)$ rapidly drops. This behavior is consistent with the data for KFe $_{2}$ As $_{2}$ and related materials. We argue that the data on $C (T)$ can be reproduced without assuming that the quasiparticle residue $Z$ on $d_{x y}$ band is small. We further argue that the very existence of a finite $T^{*} < T_{c}$ favors $s^{+-}$ gap structure over $d -$ wave, because in the latter case $T^{*}$ would vanish.

arXiv comment6 pages, 3 figures + Supplementary material. The version accepted for publication in Physical Review B

Specific heat in strongly hole-doped Iron-based superconductors

Abstract

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