Long-range coherence in a mesoscopic metal near a superconducting interface

We identify the different contributions to quantum interference in a mesoscopic 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 temperature, the magnetoresistance exhibits h/2e-periodic oscillations with 1/T power law decay. This flux-sensitive contribution arises from coherence of low-energy quasiparticle states over the phase-breaking length L(phi). Mesoscopic fluctuations contribute as a small h/e oscillation, resolved only in the purely normal state.