Cascade Boltzmann-Langevin approach to higher-order current correlations in diffusive metal contacts

The Boltzmann-Langevin approach is extended to calculations of third and fourth cumulants of current in diffusive-metal contacts. These cumulants result from indirect correlations between current fluctuations, which may be considered as noise of noise. The calculated third cumulant coincides exactly with its quantum-mechanical value. The fourth cumulant tends to its quantum-mechanical value -e(3)I/105 at high voltages and to a positive value 2e(2)T/3R at V=0 changing its sign at eVsimilar to20 T.