Dissipative Electron Transport through Andreev Interferometers

TL;DR

This paper predicts giant conductance oscillations in Andreev interferometers caused by phase differences, analyzing how scattering affects these oscillations through analytical and numerical methods.

Contribution

It introduces a detailed analysis of conductance oscillations in hybrid normal-superconductor structures, considering effects of scattering and mode mixing on the phenomenon.

Findings

Giant conductance oscillations occur at specific phase differences.

Oscillations survive in diffusive samples with potential barriers.

Path integral description explains conductance behavior.

Abstract

We consider the conductance of an Andreev interferometer, i.e., a hybrid structure where a dissipative current flows through a mesoscopic normal (N) sample in contact with two superconducting (S) "mirrors". Giant conductance oscillations are predicted if the superconducting phase difference $\phi$ is varied. Conductance maxima appear when $\phi$ is on odd multiple of $\pi$ due to a bunching at the Fermi energy of quasiparticle energy levels formed by Andreev reflections at the N-S boundaries. For a ballistic normal sample the oscillation amplitude is giant and proportional to the number of open transverse modes. We estimate using both analytical and numerical methods how scattering and mode mixing --- which tend to lift the level degeneracy at the Fermi energy --- effect the giant oscillations. These are shown to survive in a diffusive sample at temperatures much smaller than the Thouless temperature provided there are potential barriers between the sample and the normal electron reservoirs. Our results are in good agreement with previous work on conductance oscillations of diffusive samples, which we propose can be understood in terms of a Feynman path integral description of quasiparticle trajectories.