Superconducting nonequilibrium transport through a weakly interacting quantum dot

We study the out-of-equilibrium current through an interacting quantum dot, which is modeled 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 to intermediate lead-to-dot couplings.