PROXIMITY-EFFECT THEORY IN THICK NS-SANDWICHES

The tunneling density of states of plane NS sandwiches with a normal interlayer thickness d is calculated. The self-consistent account of the coordinate dependence of the order parameter both in N and S metals as well as of elastic scattering from impurities was considered. The range of the sandwich parameter values is found, where the density of states can have a double-peak structure even at perfect interface. This double-peak structure was obtained earlier in the tunnel McMillan model, which assumed the presence of the tunneling barrier between the N and S layers. Thus, the Andreev reflection effects can result in a large variety of density of states of thick NS sandwiches and, in particular, to the double-peak structure.