Semiclassical noise beyond the second cumulant

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.