Weak localization of disordered quasiparticles in the mixed superconducting state

TL;DR

This paper develops a nonlinear sigma model to describe weak localization effects on quasiparticles in disordered superconductors in the mixed state, explaining experimental thermal conductivity behavior.

Contribution

It introduces a symmetry-based supermatrix field theory for quasiparticles in disordered superconductors and links weak localization to thermal conductivity variations.

Findings

Weak localization correction affects thermal conductivity near H_c1

Zeeman splitting cuts off localization effects at low temperatures

Model explains field dependence observed in high-T_c experiments

Abstract

Starting from a random matrix model, we construct the low-energy effective field theory for the noninteracting gas of quasiparticles of a disordered superconductor in the mixed state. The theory is a nonlinear sigma model, with the order parameter field being a supermatrix whose form is determined solely on symmetry grounds. The weak localization correction to the field-axis thermal conductivity is computed for a dilute array of s-wave vortices near the lower critical field H_c1. We propose that weak localization effects, cut off at low temperatures by the Zeeman splitting, are responsible for the field dependence of the thermal conductivity seen in recent high-T_c experiments by Aubin et al.