Singular length dependence of critical current in SNS bridges

TL;DR

This paper investigates how the critical Josephson current in SNS bridges depends on the length of the normal region, revealing a nonanalytic behavior at small lengths due to extended quasiparticle states.

Contribution

It uncovers the nonanalytic length dependence of the critical current caused by extended quasiparticle states, contrasting with the localized Andreev bound states.

Findings

Critical current exhibits nonanalytic dependence on length at small L.

Extended quasiparticle states significantly influence the Josephson effect.

Contrasts the roles of extended states and Andreev bound states in SNS junctions.

Abstract

We examine dependence of the critical Josephson current on the length L of the normal bridge N between two bulk superconductors. This dependence turns out to be nonanalytic at small L. The nonanalyticity originates from the contribution of extended quasiparticle states with energies well above the superconducting gap. This should be contrasted with the more familiar contribution to the Josephson current coming from Andreev bound states localized in the normal region at energies below the gap.