LOCAL-DENSITY OF STATES IN A DIRTY NORMAL-METAL CONNECTED TO A SUPERCONDUCTOR

A superconductor in contact with a normal metal not only induces super conducting correlations, known as the proximity effect, but also modif ies the density of stares at some distance from the interface. These m odifications can be resolved experimentally in microstructured systems . We therefore study the local density of states N(E,x) of a supercond uctor-normal-metal heterostructure. We find a suppression of N(E,x) at small energies, which persists to large distances. If the normal meta l forms a thin layer of thickness L(n), a minigap in the density of st ates appears which is of the order of the Thouless energy similar to H BARD/L(n)(2). A magnetic field suppresses the features. We find good a greement with recent experiments of Gueron et al.