Shot Noise in Mesoscopic Diffusive Andreev Wires

TL;DR

This paper investigates shot noise in mesoscopic diffusive wires connected to normal and superconducting terminals, highlighting the importance of quantum coherence effects and the limitations of classical descriptions.

Contribution

It compares classical Boltzmann-Langevin and full quantum calculations, revealing anti-correlated Andreev pairs and flux-sensitive noise suppression in mesoscopic wires.

Findings

Quantum coherence causes anti-correlation of Andreev pairs for E<E_c

Full quantum calculations differ from classical models in noise predictions

Experimental confirmation of flux-sensitive suppression of effective charge

Abstract

We study shot noise in mesoscopic diffusive wires between a normal and a superconducting terminal. We particularly focus on the regime, in which the proximity-induced reentrance effect is important. We will examine the difference between a simple Boltzmann-Langevin description, which neglects induced correlations beyond the simple conductivity correction, and a full quantum calculation. In the latter approach, it turns out that two Andreev pairs propagating coherently into the normal metal are anti-correlated for E<E_c, where E_c=D/L^2 is the Thouless energy. In a fork geometry the flux-sensitive suppression of the effective charge was confirmed experimentally.