SEMICLASSICAL THEORY OF SHOT-NOISE IN MESOSCOPIC CONDUCTORS

A semiclassical theory is developed for time-dependent current fluctua tions in mesoscopic conductors. The theory is based on the Boltzmann-L angevin equation for a degenerate electron gas. The low-frequency shot -noise power is related to classical transmission probabilities at the Fermi level. For a disordered conductor with impurity scattering, it is shown how the shot noise crosses over from zero in the ballistic re gime to one-third of the Poisson noise in the diffusive regime. In a c onductor consisting of n tunnel barriers in series, the shot noise app roaches one-third of the Poisson noise as n goes to infinity, independ ent of the transparency of the barriers. The analysis confirms that ph ase coherence is not required for the occurrence of the one-third supp ression of the shot noise. The effects of electron healing and inelast ic scattering are calculated, by inserting charge-conserving electron reservoirs between segments of the conductor.