Comment on "Conductance fluctuations in mesoscopic normal-metal/superconductor samples"

TL;DR

This paper critiques a previous experimental claim of conductance fluctuation enhancement in mesoscopic Au wires with superconducting contacts, showing that the observed effect is due to contact resistance differences rather than intrinsic superconducting properties.

Contribution

It provides a correction for contact resistance effects, challenging prior claims of conductance fluctuation enhancement in superconductor-normal metal mesoscopic systems.

Findings

No significant enhancement of conductance fluctuations after correction

Contact resistance differences explain previous observations

Reevaluation of conductance fluctuation behavior in mesoscopic systems

Abstract

Recently, Hecker et al. [Phys. Rev. Lett. 79, 1547 (1997)] experimentally studied magnetoconductance fluctuations in a mesoscopic Au wire connected to a superconducting Nb contact. They claimed to have observed an enhancement of the rms magnitude of these conductance fluctuations in the superconducting state (rms(Gns)) relative to that in the normal state (rms(Gn)) by a factor of 2.8. In this comment, we argue that the measured rms(Gns) is NOT significantly enhanced compared to rms(Gn) when we correct for the presence of an incoherent series resistance from the contacts, which is different when Nb is in the superconducting or normal state.