Phase-breaking effects in superconducting heterostructures

We present a theoretical analysis of a zero-temperature charge transport in a double-barrier structure formed by normal and superconducting electrodes with a partially dephasing mesoscopic region between two insulating layers. A scattering theory approach permits us to investigate a crossover from phase-coherent to sequential carrier transmission caused by inelastic phase-randomizing events. For a weakly transmitting junction, we derive a simple expression describing their effect on the superconducting tunneling density of states. For moderate-strength barriers, numerically simulated conductance-versus-voltage spectra exhibit a double-peaked structure in the case of s-wave superconductors and a dramatic reduction of a zero-bias maximum for d-wave pairing.