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

TL;DR

This paper analyzes how the density of states and thermal conductivity in Sr₂RuO₄ vary with magnetic field orientation, impurity scattering, and temperature, revealing conditions for observable variations.

Contribution

It provides analytical expressions for vortex lattice states and explores the effects of impurities and temperature on specific heat and thermal conductivity in layered superconductors.

Findings

Differences in density of states and thermal conductivity change sign near Hc2.

Impurity scattering reduces the amplitude of angular variations.

Sign change of thermal conductivity variations occurs at low frequencies and temperatures.

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.