SUPERCONDUCTING PROXIMITY EFFECT PROBED ON A MESOSCOPIC LENGTH SCALE

We have measured by tunneling spectroscopy the electronic density of s tates in a nonsuperconducting wire in good contact with a superconduct or, at distances of 200, 300, and 800 nm from the interface. Closest t o the interface, the density of states near the Fermi energy is reduce d to 55% of its normal value. At the farthest measurement point, this dip has nearly completely disappeared. We compare our data to predicti ons based on the Usadel equations.