Suppression of Shot-Noise in Quantum Cavities: Chaos vs. Disorder

TL;DR

This paper studies how impurity scattering affects shot-noise suppression in quantum cavities, showing that impurities can restore universal noise levels under certain conditions, supporting a two-phase flow model.

Contribution

It demonstrates that impurity scattering can recover universal shot-noise behavior in quantum cavities, validating the two-phase fluid model of electronic flow.

Findings

Impurities covering the entire cavity restore the universal Fano factor.

When impurity scattering exceeds the inverse dwell time, shot-noise recovers its universal value.

Partial impurity coverage leads to saturation of shot-noise below the universal level.

Abstract

We investigate the behavior of the shot-noise power through quantum mechanical cavities in the semiclassical limit of small electronic wavelength. In the absence of impurity scattering, the Fano factor $F$, giving the noise to current ratio, was previously found to disappear as more and more classical, hence deterministic and noiseless transmission channels open up. We investigate the behavior of $F$ as diffractive impurities are added inside the cavity. We find that $F$ recovers its universal value provided (i) impurities cover the full cavity so that only a set of zero measure of classical trajectories may avoid them, and (ii) the impurity scattering rate exceeds the inverse dwell time through the cavity. If condition (i) is not satisfied, $F$ saturates below its universal value, even in the limit of strong scattering. Our results corroborate the validity of the two-phase fluid model according to which the electronic flow splits into two well separated components, a classical deterministic fluid and a stochastic quantum-mechanical fluid. Only the latter carries shot-noise.