LONG-RANGE COHERENCE IN A MESOSCOPIC METAL NEAR A SUPERCONDUCTING INTERFACE

We identify the different contributions to quantum interference in a m esoscopic metallic loop in contact with two superconducting electrodes . At low temperature, a hurt-modulated Josephson coupling is observed with strong damping over the thermal length L(T). At higher temperatur e, the magnetoresistance exhibits h/2e-periodic oscillations with 1/T power law decay. This flux-sensitive contribution arises from coherenc e of low-energy quasiparticle states over the phase-breaking length L( phi). Mesoscopic fluctuations contribute as a small h/e oscillation, r esolved only in the purely normal state.