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. © 2006 The American Physical Society.