Re-entrance of the metallic conductance in a mesoscopic proximity superconductor

TL;DR

This paper experimentally investigates how metallic conductance re-enters in a mesoscopic normal metal-superconductor system at very low temperatures, influenced by bias voltage and magnetic flux, with results aligning with quasiclassical theory.

Contribution

It demonstrates the re-entrance of metallic conductance in a mesoscopic regime and explores its dependence on bias voltage and magnetic flux, supported by experimental data and theoretical modeling.

Findings

Re-entrance of metallic conductance observed at low temperatures.

Bias voltage suppresses the re-entrance effect.

Magnetic flux enhances the re-entrance phenomenon.

Abstract

We present an experimental study of the diffusive transport in a normal metal near a superconducting interface, showing the re-entrance of the metallic conductance at very low temperature. This new mesoscopic regime comes in when the thermal coherence length of the electron pairs exceeds the sample size. This re-entrance is suppressed by a bias voltage given by the Thouless energy and can be strongly enhanced by an Aharonov Bohm flux. Experimental results are well described by the linearized quasiclassical theory.