Nonequilibrium Noise in Metals at Mesoscopic Scales

We analyze high-field current fluctuations in degenerate conductors by mapping the electronic Fermi-liquid correlations at equilibrium to their semiclassical non-equilibrium form. Our resulting Boltzmann description is applicable to diffusive mesoscopic wires. We derive a non-equilibrium connection between thermal fluctuations of the current and resistive dissipation. In the weak-field limit this is the canonical fluctuation- dissipation theorem. Away from equilibrium, the co...

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 therm...

We argue, physically and formally, that existing diffusive models of noise yield inaccurate microscopic descriptions of nonequilibrium current fluctuations. The theoretical shortfall becomes pronounced in quantum-confined metallic systems, such as the two-dimensional electron gas. In such systems we propose a simple experimental test of mesoscopic validity for diffusive theory's central claim: the smooth crossover between Johnson-Nyquist and shot noise.

A semiclassical theory is developed for time-dependent current fluctuations in mesoscopic conductors. The theory is based on the Boltzmann-Langevin 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 regime to one-third of the Poisson noise in the diffusive regi...

A short summary of the drift-diffusion-Langevin formalism for calculating finite-frequency shot noise in diffusive conductors is presented. Two new results are included in this presentation. First, we arrive at a simple (but accurate) phenomenological expression for the semiclassical distribution function of electrons in the presence of electron-electron scattering. Second, it is shown that in thin samples, low-frequency shot noise may be large even if the sample length is mu...

In the theory of noise processes for mesoscopic conductors, the relationship between shot noise and hot-electron noise is absolutely fundamental to understanding the underlying microscopic fluctuations. From the vantage point of orthodox microscopics and kinetics, their relation is a long way from being settled. Its resolution calls for the tools of many-body theory. We motivate the many-body approach to noise, review the analysis of conductance and current noise within linea...

Coulomb screening, together with degeneracy, is characteristic of the metallic electron gas. While there is little trace of its effects in transport and noise in the bulk, at mesoscopic scales the electronic fluctuations start to show appreciable Coulomb correlations. Within a strictly standard Boltzmann and Fermi-liquid framework, we analyze these phenomena and their relation to the mesoscopic fluctuation-dissipation theorem, which we prove. We identify two distinct screenin...

Microscopic current fluctuations are inseparable from conductance. We give an integral account of both quantized conductance and nonequilibrium thermal noise in one-dimensional ballistic wires. Our high-current noise theory opens a very different window on such systems. Central to the role of nonequilibrium ballistic noise is its direct and robust dependence on the statistics of carriers. For, with increasing density, they undergo a marked crossover from classical to strongly...

Theoretical and experimental work concerned with dynamic fluctuations has developed into a very active and fascinating subfield of mesoscopic physics. We present a review of this development focusing on shot noise in small electric conductors. Shot noise is a consequence of the quantization of charge. It can be used to obtain information on a system which is not available through conductance measurements. In particular, shot noise experiments can determine the charge and stat...

It is shown that electron-electron interactions lead to a novel quantum-interference contribution to non-equilibrium current noise in mesoscopic conductors. The corresponding noise spectrum is obtained in detail for diffusive systems. It is found to be quadratic in the applied voltage and to exhibit a power-law frequency spectrum whose exponent depends on the dimensionality of the sample.