Long-Range Coherence in a Mesoscopic Metal near a Superconducting Interface

Abstract
We identify the different contributions to quantum interference in a mesoscopic metallic loop in contact with two superconducting electrodes. At low temperature, a flux-modulated Josephson coupling is observed with strong damping over the thermal length LT. 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 Lϕ. Mesoscopic fluctuations contribute as a small h/e oscillation, resolved only in the purely normal state.
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