Proximity Effect in Presence of Quantum Fluctuations

TL;DR

This paper investigates how Coulomb interactions influence the superconductive proximity effect in disordered metals, revealing the roles of Coulomb-induced suppression of tunneling density of states and enhanced repulsion in the Cooper channel at low temperatures.

Contribution

It introduces a Keldysh functional approach to analyze Coulomb effects on the proximity effect in disordered metals, providing new insights into subgap conductance and Josephson coupling.

Findings

Coulomb interactions suppress subgap Andreev conductance.

Disorder-enhanced Coulomb repulsion affects Josephson coupling.

Both effects are significant at low temperatures.

Abstract

The effect of Coulomb interaction upon superconductive proximity effect in disordered metals is studied, employing newly developed Keldysh functional approach (cond-mat/9907358). We have calculated subgap Andreev conductance between superconductor and 2D dirty film, as well as Josephson coupling via such a film. Both two qualitatively different Coulomb effects - suppression of the tunneling density of states and disorder-enchanced repulsion in the Cooper channel - are shown to be important at sufficiently low temperatures.