Effect of potential fluctuations on shot noise suppression in mesoscopic cavities

TL;DR

This study numerically examines how impurity-induced potential fluctuations influence shot noise in mesoscopic cavities, revealing that disorder leads to diffusive behavior rather than chaotic regimes, affecting noise suppression levels.

Contribution

It demonstrates that potential fluctuations from impurities do not induce chaos but cause diffusive noise behavior, emphasizing the importance of material purity for shot noise suppression.

Findings

Disorder dominates noise behavior when potential fluctuations are comparable to Fermi energy.

The 1/4 shot noise suppression is only achievable in high-quality, low-impurity materials.

Increasing disorder transitions the suppression factor from 1/4 to diffusive values.

Abstract

We perform a numerical investigation of the effect of the disorder associated with randomly located impurities on shot noise in mesoscopic cavities. We show that such a disorder becomes dominant in determining the noise behavior when the amplitude of the potential fluctuations is comparable to the value of the Fermi energy and for a large enough density of impurities. In contrast to existing conjectures, random potential fluctuations are shown not to contribute to achieving the chaotic regime whose signature is a Fano factor of 1/4, but, rather, to the diffusive behavior typical of disordered conductors. In particular, the 1/4 suppression factor expected for a symmetric cavity can be achieved only in high-quality material, with a very low density of impurities. As the disorder strength is increased, a relatively rapid transition of the suppression factor from 1/4 to values typical of diffusive or quasi-diffusive transport is observed. Finally, on the basis of a comparison between a hard-wall and a realistic model of the cavity, we conclude that the specific details of the confinement potential have a minor influence on noise.