Current-voltage characteristics of superconductor-normal metal-superconductor junctions

TL;DR

This paper develops a theoretical model for the current-voltage characteristics of SNS junctions, highlighting the roles of inelastic and elastic relaxation times at different voltage regimes.

Contribution

It introduces a comprehensive theory linking I-U characteristics to relaxation times and the density of states in SNS junctions, emphasizing phase dependence.

Findings

Linear conductance proportional to inelastic relaxation time at low voltages

I-U characteristics depend on the density of states and phase difference

At high voltages, elastic relaxation time dominates the behavior

Abstract

We develop a theory of current-voltage (I-U) characteristics for superconductor-normal metal-superconductor (SNS) junctions. At small voltages and sufficiently low temperatures the I-U characteristics of the junction is controlled by the inelastic relaxation time, \tau_{in}. In particular, the linear conductance is proportional to, \tau_{in}. In this regime the I-U characteristics can be expressed solely in terms of dependence of the density of states in the normal region, \nu(\chi), on the phase difference of the order parameter across the the junction. In contrast, at large voltages the I-U characteristics of the device is controlled by the elastic relaxation time, \tau_{el}, which is much smaller than the inelastic one.