Nonlinear shot noise in mesoscopic diffusive normal-superconducting systems

TL;DR

This paper investigates nonlinear shot noise in mesoscopic diffusive NS systems at finite voltages, revealing a reentrant voltage dependence due to the proximity effect and analyzing the impact of barriers on noise characteristics.

Contribution

It introduces a numerical scattering-matrix approach to study nonlinear shot noise and the differential Fano factor in NS heterostructures with and without barriers.

Findings

Shot noise exhibits reentrant voltage dependence due to proximity effect.

Differential Fano factor remains approximately constant across voltages.

Barrier height significantly influences the differential Fano factor.

Abstract

We study differential shot noise in mesoscopic diffusive normal-superconducting (NS) heterostructures at finite voltages where nonlinear effects due to the superconducting proximity effect arise. A numerical scattering-matrix approach is adopted. Through an NS contact, we observe that the shot noise shows a reentrant dependence on voltage due to the superconducting proximity effect but the differential Fano factor stays approximately constant. Furthermore, we consider differential shot noise in the structures where an insulating barrier is formed between normal and superconducting regions and calculate the differential Fano factor as a function of barrier height.