Heat transport in nonuniform superconductors

TL;DR

This paper develops a self-consistent theoretical framework to analyze heat transport in inhomogeneous superconductors with domain walls, revealing how bound states and impurity effects influence thermal conductivity.

Contribution

It introduces a comprehensive non-equilibrium quasiclassical approach to study heat transport in nonuniform superconductors with domain walls, highlighting the role of bound states and impurity interactions.

Findings

Heat transport is anisotropic and non-local in the presence of domain walls.

Bound states significantly modify quasiparticle spectra and facilitate Andreev reflection.

Transport across domain walls is more efficient at low temperatures with strong impurity scattering.

Abstract

We calculate electronic energy transport in inhomogeneous superconductors using a fully self-consistent non-equilibrium quasiclassical Keldysh approach. We develop a general theory and apply it a superconductor with an order parameter that forms domain walls, of the type encountered in Fulde-Ferrell-Larkin-Ovchinnikov state. The heat transport in the presence of a domain wall is inherently anisotropic and non-local. Bound states in the nonuniform region play a crucial role and control heat transport in several ways: (i) they modify the spectrum of quasiparticle states and result in Andreev reflection processes, and (ii) they hybridize with impurity band and produce local transport environment with properties very different from those in uniform superconductor. As a result of this interplay, heat transport becomes highly sensitive to temperature, magnetic field and disorder. For strongly scattering impurities we find that the transport across domain walls at low temperatures is considerably more efficient than in the uniform superconducting state.