Multiparticle tunneling in diffusive superconducting junctions

TL;DR

This paper develops a theoretical framework for understanding multiparticle tunneling in diffusive superconducting junctions, revealing significantly different scaling behaviors compared to ballistic counterparts.

Contribution

It introduces a novel approach combining circuit theory and perturbation expansion to analyze nonequilibrium superconductors with diffusive electrodes.

Findings

Greater scaling parameter for subharmonic gap structure in diffusive junctions

Theoretical prediction of differences between diffusive and ballistic junctions

Enhanced understanding of multiparticle current transport mechanisms

Abstract

We formulate a theoretical framework to describe multiparticle current transport in planar superconducting tunnel junctions with diffusive electrodes. The approach is based on direct solving of quasiclassical Keldysh-Green function equations for nonequilibrium superconductors, and consists of a combination of a circuit theory analysis and improved perturbation expansion. The theory predicts much greater scaling parameter for the subharmonic gap structure of the tunnel current in diffusive junctions compared to the one in ballistic junctions and mesoscopic constrictions with the same barrier transparency.