Supercurrent dephasing by electron-electron interactions

TL;DR

This paper shows that electron-electron interactions cause exponential suppression of the supercurrent in long diffusive SNS junctions at zero temperature due to Cooper pair dephasing, introducing a new length scale $L_\varphi$.

Contribution

It identifies a fundamental dephasing length scale $L_\varphi$ caused by electron-electron interactions in SNS junctions, affecting supercurrent behavior at zero temperature.

Findings

Supercurrent is exponentially suppressed by interactions.

Dephasing length $L_\varphi$ can be extracted from measurements.

Dephasing occurs in the normal metal, affecting Josephson current.

Abstract

We demonstrate that in sufficiently long diffusive superconducting-normal-superconducting ($SNS$) junctions dc Josephson current is exponentially suppressed by electron-electron interactions down to zero temperature. This suppression is caused by the effect of {\it Cooper pair dephasing} which occurs in the normal metal and defines a new fundamental length scale $L_\varphi$ in the problem. Provided the temperature length exceeds $L_\varphi$ this dephasing length can be conveniently extracted from equilibrium measurements of the Josephson current.