The spectral conductance of a proximity superconductor and the re-entrance effect

TL;DR

This paper investigates the spectral conductance in proximity superconductor systems, combining theoretical models with experimental data to understand the re-entrance effect and energy distribution of conduction electrons.

Contribution

It provides a comprehensive analysis of how spectral conductance depends on various parameters and introduces experimental observations of the re-entrance effect at very low temperatures.

Findings

Spectral conductance depends on phase-breaking length, superconductor gap, and interface transparency.

Experimental evidence of re-entrance of normal-state conductance at low temperature and bias.

Heating effects are crucial for accurate interpretation of experimental data.

Abstract

In a mesoscopic metal in proximity with a superconductor, the electronic conductance is enhanced in a very energy-sensitive way. In this paper, we discuss the spectral conductance of a proximity superconductor from both the theoretical and experimental point of view. The dependence of the spectral conductance on the phase-breaking length, gap of the superconductor and interface transparency is theoretically investigated. We present experimental data on the re-entrance of the normal-state conductance at very low temperature and bias voltage. A complete description of the experimental data needs taking into account heating of the reservoirs by the bias current. In addition, we show that the energy sensitivity of the proximity effect enables one to access the energy distribution of the conduction electrons inside a mesoscopic sample.