Doubled Full Shot Noise in Quantum Coherent Superconductor - Semiconductor Junctions

TL;DR

This paper reports on low-temperature shot noise measurements in superconductor-semiconductor junctions, revealing doubled shot noise due to coherent reflections and a transition to normal noise with quasiparticle effects.

Contribution

It demonstrates the doubling of shot noise in superconductor-semiconductor junctions caused by coherent multiple reflections, a novel observation in this context.

Findings

Shot noise is doubled (S=4eI) at low energies due to coherence.

Shot noise reverts to normal (S=2eI) when quasiparticles dominate.

Conductance peaks are linked to coherent multiple reflections.

Abstract

We performed low temperature shot noise measurements in Superconductor (TiN) - strongly disordered normal metal (heavily doped Si) weakly transparent junctions. We show that the conductance has a maximum due to coherent multiple reflections at low energy and that shot noise is then twice the Poisson noise (S=4eI). The shot noise changes to the normal value (S=2eI) due to a large quasiparticle contribution.