Current noise and Coulomb effects in superconducting contacts

TL;DR

This paper derives an effective action for superconducting contacts, analyzing Coulomb and noise effects on conductance and Josephson current, revealing their dependence on contact transparency and temperature.

Contribution

It introduces a unified framework to evaluate Coulomb and noise effects in superconducting contacts with arbitrary transmission, connecting these effects to measurable quantities.

Findings

Interaction corrections vanish for fully transparent contacts at zero temperature.

Coulomb effects are closely related to shot noise in NS systems.

Electron-electron interactions influence Josephson current in SS contacts.

Abstract

We derive an effective action for contacts between superconducting terminals with arbitrary transmission distribution of conducting channels. In the case of normal-superconducting (NS) contacts we evaluate interaction correction to Andreev conductance and demonstrate a close relation between Coulomb effects and shot noise in these systems. In the case of superconducting (SS) contacts we derive the electron-electron interaction correction to the Josephson current. At $T=0$ both corrections are found to vanish for fully transparent NS and SS contacts indicating the absence of Coulomb effects in this limit.