Proximity effect and multiple Andreev reflections in diffusive superconductor–normal-metal–superconductor junctions

We present a theory of the current-voltage characteristics in diffusive superconductor--normal-metal--superconductor junctions. By solving the time-dependent Usadel equations we are able to describe the phase-coherent transport for arbitrary length of the normal wire. We show how the interplay between proximity effect and multiple Andreev reflections gives rise to a rich subgap structure in the conductance and how it is revealed in the nonequilibrium distribution function.