Andreev Reflection Enhanced Shot Noise in Mesoscopic SNS Junctions

TL;DR

This paper investigates shot noise in mesoscopic Nb-Al-Nb SNS junctions, confirming doubled shot noise due to Andreev reflections and examining the effects of magnetic fields and heat dissipation.

Contribution

It provides experimental evidence of Andreev reflection enhanced shot noise in mesoscopic SNS junctions and discusses heat dissipation and magnetic field effects.

Findings

Shot noise amplitude matches theoretical doubling due to Andreev reflections.

Weak magnetic field halves the 1/f noise amplitude.

Sample remains in the mesoscopic regime far from equilibrium.

Abstract

Current noise is measured with a SQUID in low impedance and transparent Nb-Al-Nb j unctions of length comparable to the phase breaking length and much longer than the thermal length. The shot noise amplitude is compared with theoretical predictions of doubled shot noise in diffusive normal/superconductor (NS) junctions due to the Andreev reflections. We discuss the heat dissipation away from the normal part through the NS interfaces. A weak applied magnetic field reduces the amplitude of the 1/f noise by a factor of two, showing that even far from equilibrium the sample is in the mesoscopic regime.