Finite voltage shot noise in normal-metal - superconductor junctions

TL;DR

This paper derives an expression for low-frequency shot noise in disordered normal-metal–superconductor junctions at finite voltage, revealing conductance resonances and noise enhancements linked to Andreev reflections and multichannel effects.

Contribution

It provides a new theoretical framework connecting shot noise with scattering amplitudes and Andreev reflections in NS junctions, highlighting resonance phenomena.

Findings

Conductance shows resonances at multichannel limits.

Shot noise is enhanced during resonances.

Transport properties differ at low versus high voltages.

Abstract

We express the low-frequency shot noise in a disordered normal-metal - superconductor (NS) junction at finite (subgap) voltage in terms of the normal scattering amplitudes and the Andreev reflection amplitude. In the multichannel limit, the conductance exhibits resonances which are accompanied by an enhancement of the (differential) shot noise. In the study of multichannel single and double barrier junctions we discuss the noise properties of coherent transport at low versus high voltage with respect to the Andreev level spacing.