Mesoscopic conductance fluctuations in InAs nanowire-based SNS junctions

TL;DR

This study investigates mesoscopic conductance fluctuations in Nb/InAs-nanowire/Nb SNS devices, revealing their temperature dependence, non-linear bias behavior, and connection to dephasing and Andreev reflections, providing insights into quantum transport phenomena.

Contribution

It presents the first systematic experimental analysis of conductance fluctuations in InAs nanowire SNS junctions, linking fluctuations to dephasing and Andreev processes.

Findings

Fluctuations exceed normal state values and depend strongly on temperature.

Conductance fluctuations are non-linear in bias voltage and show sub-gap features.

Results are explained by multiple Andreev reflections in chaotic quantum dots.

Abstract

We report a systematic experimental study of mesoscopic conductance fluctuations in superconductor/normal/superconductor (SNS) devices Nb/InAs-nanowire/Nb. These fluctuations far exceed their value in the normal state and strongly depend on temperature even in the low-temperature regime. This dependence is attributed to high sensitivity of perfectly conducting channels to dephasing and the SNS fluctuations thus provide a sensitive probe of dephasing in a regime where normal transport fails to detect it. Further, the conductance fluctuations are strongly non-linear in bias voltage and reveal sub-gap structure. The experimental findings are qualitatively explained in terms of multiple Andreev reflections in chaotic quantum dots with imperfect contacts.