Thermal conductivity in the vortex state of YBa_2Cu_3O_7 and Sr_2RuO_4

TL;DR

This paper develops a theoretical model to calculate the thermal conductivity in the vortex state of high-temperature superconductors YBa_2Cu_3O_7 and Sr_2RuO_4, considering impurity and Andreev scattering effects.

Contribution

It introduces a self-consistent calculation of impurity and Andreev scattering rates in the vortex state for d-wave and triplet pairing superconductors.

Findings

Point-like impurity scattering models do not match experimental data in YBCO.

The theory applies to both d-wave and triplet pairing states with line nodes.

Impurity effects are crucial for understanding thermal conductivity in these materials.

Abstract

The thermal conductivity $\kappa$ is calculated for the Abrikosov vortex lattice with d-wave pairing. The Andreev scattering rate arises from the self energy term in Gorkov's integral equation for the corresponding Green's function. The impurity scattering rate is calculated self-consistently from this Green's function in the t-matrix approximation. Neither point-like impurity scattering with a phase shift in the almost unitary limit nor in the Born limit can consistently explain recent zero-field and finite-field measurements of $\kappa/T$ at low $T$ in ultraclean YBCO. Our theory also applies to the spin triplet pairing states with vertical or horizontal line nodes in Sr$_2$RuO$_4$