Multiple Andreev reflections in diffusive SINIS and SIFIS junctions

Abstract

We study Multiple Andreev Reflections in long diffusive superconductor(S)-normal metal(N)-superconductor junctions with low-transparency interfaces. Assuming strong thermalization in the weak link, we calculate the current-voltage dependence I(V)I(V). At intermediate temperatures, \varepsilon_\mathrm{Th}\ll T\ll\DeltaεTh≪T≪Δ, the current is dominated by noncoherent multiple Andreev reflections and is obtained analytically. The results are generalized to a ferromagnetic junction. We find that the exchange field produces a non-trivial splitting of the subharmonic gap structure. This effect relies on thermalization and vanishes in SFS junctions with no energy relaxation in the weak link.