High-field noise in degenerate and mesoscopic systems

We analyse high-field current fluctuations in metallic systems by direct mapping of the Fermi-liquid correlations to the semiclassical nonequilibrium state. We give three applications. First, for bulk conductors, we show that there is a unique nonequilibrium analogue to the fluctuation-dissipation theorem for thermal noise. With it, we calculate suppression of the excess hot-electron term by Pauli exclusion. Second, in the degenerate regime, we argue that shot noise and thermal noise are incommensurate. They cannot be connected by a smooth, universal interpolation formula. This follows from their contrasting responses to Coulomb screening. We propose an experiment to test this mismatch. Third, we carry out an exact model calculation of high-field shot noise in narrow mesoscopic wires. We show that a distinctive mode of suppression arises from the structure of the semiclassical Boltzmann equation in two and three dimensions. In one dimension such a mode does not exist.