Theory of AC Josepson Effect in Superconducting Constrictions

TL;DR

This paper develops a comprehensive microscopic theory for the ac Josephson effect in superconducting constrictions, accounting for various electron transport regimes and electrode structures, with applications to subgap current features.

Contribution

It introduces a unified microscopic framework for the ac Josephson effect applicable to ballistic and diffusive constrictions with arbitrary electrode structures.

Findings

Smearing of subgap current singularities by pair-breaking effects.

Structure of singularities in S/N constrictions with proximity-induced gaps.

Theory's applicability to diverse microscopic configurations.

Abstract

We have developed a microscopic theory of ac Josephson effect in short ballistic superconducting constrictions with arbitrary electron transparency and in constrictions with diffusive electron transport. The theory is valid for arbitrary miscroscopic structure of the superconducting electrodes of the constriction. As applications of the theory we study smearing of the subgap current singularities by pair-breaking effects and also the structure of these singularities in the constrictions between the composite S/N electrodes with the proximity-induced gap in the normal layer.