Specific heat and thermal conductivity in Sr_2RuO_4 for rotating in-plane magnetic field

Abstract

We calculate the density of states $N$ and the the thermal conductivity $\kappa$ in layered superconductors for rotating in-plane magnetic field by using approximate analytical expressions for Abrikosov's vortex lattice state. For a gap with d${}_{xy}$- orbital symmetry we find that the differences $\Delta N$ and $\Delta \kappa$ between field directions parallel to the antinodes and parallel to the nodes of the gap are positive for lower fields and change sign for higher fields near $H_{c2}$. For increasing impurity scattering, $\Delta N$ and $\Delta \kappa$ decrease due to a broadening of certain peaks in the angle-resolved density of states. The frequency dependencies of the amplitudes $\Delta N$ and $\Delta \kappa$ exhibit similar crossover behavior at low frequencies which give rise to a sign change of $\Delta \kappa$ at low $T/T_c$. We conclude that variations of the specific heat and thermal conductivity can be observed only in the clean and low temperature limits.

Submitted to Physical Review B