Superconducting Proximity Effect and Universal Conductance Fluctuations

TL;DR

This paper investigates how superconductivity influences universal conductance fluctuations in mesoscopic N-S-N structures, revealing suppression of fluctuations and distinct responses to magnetic fields and phase variations.

Contribution

It provides a numerical analysis of UCFs in N-S-N structures, highlighting differences from N-S structures and the effects of quasiparticle transmission presence.

Findings

Superconductivity suppresses UCFs in N-S-N structures.

Open and closed structures respond differently to magnetic fields.

Distinct phase variation responses observed in different structures.

Abstract

We examine universal conductance fluctuations (UCFs) in mesoscopic normal-superconducting-normal (N-S-N) structures using a numerical solution of the Bogoliubov - de Gennes equation. We discuss two cases depending on the presence (``open'' structure) or absence (``closed'' structure) of quasiparticle transmission. In contrast to N-S structures, where the onset of superconductivity increases fluctuations, we find that UCFs are suppressed by superconductivity for N-S-N structures. We demonstrate that the fluctuations in ``open'' and ``closed'' structures exhibit distinct responses to an applied magnetic field and to an imposed phase variation of the superconducting order parameter.