Thermal conductivity in the vortex state of the superconductor UPd_2Al_3

TL;DR

This paper calculates the thermal conductivity in the vortex state of UPd_2Al_3 superconductor, considering effects of supercurrent and scattering, and compares results with experiments to understand gap structure.

Contribution

It introduces a Green's function approach to model thermal conductivity considering vortex effects and compares multiple gap functions with experimental data.

Findings

Qualitative agreement with experiments for certain gap functions

Thermal conductivity depends on field strength, impurity scattering, and temperature

Horizontal line nodes at specific ck_z values are consistent with observations

Abstract

The magneto-thermal conductivity kappa is calculated for the vortex state of UPd_2Al_3 by assuming horizontal gap nodes. The Green's function method we employed takes into account the effects of supercurrent flow and Andreev scattering on the quasiparticles due to Abrikosov's vortex lattice order parameter. The calculated angular dependence of kappa_{yy} for field rotation theta_0 in the ac-plane depends strongly on field strength H, impurity scattering, anisotropy of the Fermi velocity, and temperature. For finite temperatures and the clean unitary scattering limit we get qualitative agreement with recent experiments for all four proposed gap functions having horizontal line nodes at ck_z = 0, pi/4, and pi/2.