Quasiparticle current in ballistic NcN'S junctions

Nonstationary properties of ballistic constrictions NcN'S with disordered N'S electrodes are analyzed theoretically. Amplitudes of Andreev and normal reflections at the constriction are related to the solutions of a stationary Green's function problem in an inhomogeneous N'S electrode in a dirty limit. This provides a generalization of the model of Blender, Tinkham and Klapwijk for a spatially inhomogeneous case. The relation between quasiparticle current in NcN'S junctions and the energy spectrum of a N'S proximity sandwich is found for arbitrary parameters of N' and S materials and of the N'S interface.