Self-consistent theory of transport in superconducting wires

TL;DR

This paper develops a comprehensive self-consistent theoretical framework to analyze superconducting transport in wires under various conditions, including equilibrium and nonequilibrium states, disorder levels, and current densities.

Contribution

It introduces a unified quasiclassical Green's function approach that accounts for arbitrary disorder and current, providing detailed predictions of superconducting properties under diverse conditions.

Findings

Current-induced gapless superconductivity can be achieved in clean wires.

Nonequilibrium conditions enhance the stability of gapless states.

Profiles of electrostatic potential and order parameter are characterized under various regimes.

Abstract

We study superconducting transport in homogeneous wires in the cases of both equilibrium and nonequilibrium quasiparticle populations, using the quasiclassical Green's function technique. We consider superconductors with arbitrary current densities and impurity concentrations ranging from the clean to the dirty limit. Local current conservation is guaranteed by ensuring that the order parameter satisfies the self-consistency equation at each point. For equilibrium transport, we compute the current, the order parameter amplitude, and the quasiparticle density of states as a function of the superfluid velocity, temperature, and disorder strength. Nonequilibrium is characterized by incoming quasiparticles with different chemical potentials at each end of the superconductor. We calculate the profiles of the electrostratic potential, order parameter, and effective quasiparticle gap. We find that a transport regime of current-induced gapless superconductivity can be achieved in clean superconductors, the stability of this state being enhanced by nonequilibrium.