PROXIMITY EFFECT OF THIN-FILMS ON SUPERCONDUCTING SUBSTRATES

We calculate the local density of states for a thin metallic film deposited on a superconducting substrate. We use a tight-binding model with a BCS interaction in the substrate. We show that for energies lower than the superconducting gap of the substrate, the local density of states in the normal metal film presents a structure due to the proximity effect. In very thin normal films, we obtain a structure that was missed in previous calculations. We interpret recent experiments in Au-NbSe2 systems in terms of this structure.