Energy dependence of current noise in superconducting/normal metal junctions

TL;DR

This paper derives a general expression for how current noise varies with energy in diffusive metal-superconductor junctions, considering arbitrary interface transparencies, extending understanding beyond limited cases.

Contribution

It introduces a comprehensive quasiclassical theory for current fluctuations, accounting for arbitrary channel transparencies in diffusive conductors connected to superconductors.

Findings

Provides a general formula for energy-dependent current noise.

Extends analysis beyond known limiting cases.

Enhances understanding of noise behavior in superconductor-normal metal junctions.

Abstract

Interference of electronic waves undergoing Andreev reflection in diffusive conductors determines the energy profile of the conductance on the scale of the Thouless energy. A similar dependence exists in the current noise, but its behavior is known only in few limiting cases. We consider a metallic diffusive wire connected to a superconducting reservoir through an interface characterized by an arbitrary distribution of channel transparencies. Within the quasiclassical theory for current fluctuations we provide a general expression for the energy dependence of the current noise.