Andreev-reflection-induced conductance diffraction in mesoscopic normal-metal/Superconductor interfaces

Abstract

We observed conductance oscillations, which arose from the interference of quasiparticles Andreev-reflected from a mesoscopic single normal-metal/superconductor (N/S) interface with a phase gradient along its width. A 10 x 10 mum(2) Al island was overlaid on a pre-evaporated 0.5-mum-wide silver wire. The phase gradient along the N/S interface was induced by applying it magnetic field perpendicular to the plane of the superconducting Al island. The conductance across the N/S interface showed Fraunhofer-like oscillations with amplitudes of a small fraction or 2e(2)/h. For sufficiently low fields and temperatures, this interfacial diffraction effect of quasiparticles; is more complicated due to the field-induced electron-hole dephasing effect. The overall magnetic-field and temperature dependencies of the conductance oscillations are qualitatively consistent with the predicted diffraction of Andreev-reflected quasiparticles.