Semiclassical noise beyond the second cumulant

TL;DR

This paper extends the semiclassical Langevin approach to calculate higher-order noise cumulants, revealing complex correlations and frequency-dependent features in mesoscopic systems, with implications for understanding noise in quantum conductors.

Contribution

It introduces a diagrammatic method for computing higher cumulants of noise beyond the second, applicable to mesoscopic conductors and chaotic cavities.

Findings

Higher cumulants are influenced by indirect correlations, termed 'noise of noise'

The third cumulant exhibits unique frequency-dependent features

Environmental feedback impacts the measurement of higher cumulants

Abstract

We show how the semiclassical Langevin method can be extended to calculations of higher-than-second cumulants of noise. These cumulants are affected by indirect correlations between the fluctuations, which may be considered as "noise of noise." We formulate simple diagrammatic rules for calculating the higher cumulants and apply them to mesoscopic diffusive contacts and chaotic cavities. As one of the application of the method, we analyze the frequency dependence of the third cumulant of current in these systems and show that it contains additional peculiarities as compared to the second cumulant. The effects of environmental feedback in measurements of the third cumulant are also discussed in terms of this method.