Critical voltage of a mesoscopic superconductor

TL;DR

This paper investigates how a non-thermal quasiparticle distribution, induced by bias voltage, influences the superconducting-to-normal transition in mesoscopic superconductors using numerical solutions of the Usadel equation.

Contribution

It reveals that the energy mode of the quasiparticle distribution causes a first order transition independent of current, extending understanding beyond linear response.

Findings

Non-thermal distribution f caused by bias voltage

Energy mode f_L drives first order transition

Transition occurs irrespective of current

Abstract

We study the role of the quasiparticle distribution function f on the properties of a superconducting nanowire. We employ a numerical calculation based upon the Usadel equation. Going beyond linear response, we find a non-thermal distribution for f caused by an applied bias voltage. We demonstrate that the even part of f (the energy mode f_L) drives a first order transition from the superconducting state to the normal state irrespective of the current.