Superconducting non-equilibrium transport through a weakly interacting quantum dot

TL;DR

This paper investigates the non-equilibrium current in a superconducting quantum dot system with interactions, revealing an unexpected current enhancement due to repulsive interactions using a novel Green's function approach.

Contribution

It introduces a perturbative Keldysh Green's function method to analyze non-equilibrium transport in interacting superconducting quantum dots, accounting for multiple Andreev reflections.

Findings

Repulsive interactions can enhance current at small lead-to-dot couplings.

Develops a new perturbative scheme for out-of-equilibrium superconducting quantum dots.

Provides insights into non-trivial effects of interactions on superconducting transport.

Abstract

We study the out-of-equilibrium current through an interacting quantum dot modelled as an Anderson impurity contacted by two BCS superconductors held at fixed voltage bias. In order to account for multiple Andreev reflections, we develop a Keldysh Green's function scheme perturbative in the dot's interaction strength. We find an unexpected enhancement of the current due to repulsive interactions for small lead-to-dot couplings.