Coulomb Effects in Nanoscale SINIS Junction

TL;DR

This paper investigates how Coulomb interactions affect the Josephson effect in nanoscale SINIS junctions, revealing complex temperature-dependent behaviors and the potential for charge control via gating.

Contribution

It provides a detailed analysis of Coulomb effects on Josephson current and minigap in SINIS junctions, including temperature dependence and the role of gate electrodes.

Findings

Coulomb repulsion suppresses coherent charge transport.

Gate electrodes can enhance current by relaxing charge blockade.

Temperature and Coulomb interaction can cause nonmonotonous and reentrant behaviors.

Abstract

We study the system of two superconductors connected by a small normal grain. We consider the modification of the Josephson effect by the Coulomb interaction on the grain. Coherent charge transport through the junction is suppressed by Coulomb repulsion. An optional gate electrode may relax the charge blocking and enhance the current leading to the single Cooper pair transistor effect. Temperature dependences of critical current and of the minigap induced in the normal grain by the proximity to superconductor are studied. Both temperature and Coulomb interaction suppress critical current and minigap but their interplay may lead to the nonmonotonous and even reentrant temperature dependence.