TRANSPORT AND NOISE IN MULTI-TERMINAL DIFFUSIVE CONDUCTORS

摘要

Shot-noise induced by current or voltage fluctuations in electron transport is a striking manifestation of charge quantization (for a review, see). It serves as a sensitive tool to study correlations in conductors: while shot-noise assumes a maximum value (with Poissonian distribution) in the absence of correlations, it becomes suppressed when correlations set in as e.g. imposed by the Pauli principle. In diffusive mesoscopic two-terminal conductors where the inelastic scattering lengths exceed the system size the shot-noise suppression factor was predicted to be 1/3. The 1/3-suppression of shot-noise in diffusive conductors is now experimentally confirmed. While some derivations are based on a scattering matrix approach and thus a priori include quantum phase coherence, no such effects are included in the semiclassical Boltzmann-Langevin equation approach, which nevertheless leads to the same result. However, while in the quantum approach for a two-terminal conductor the factor 1/3 was even shown to be universal, the semiclassical derivations given so far are restricted to quasi-one-dimensional conductors. We present here the theory of transport and noise in multiterminal diffusive conductors. This problem has been recently addressed by Blanter and Buettiker in Ref. where they use the scattering matrix formulation followed by an impurity averaging procedure. Having the advantage of including quantum phase coherence, this approach is somewhat cumbersome to generalize to an arbitrary geometry and arbitrary disorder. In contrast to this, our approach is based on a semiclassical Boltzmann-Langevin equation, which greatly simplifies the calculations. In Section 2. we formulate hte problem and give a formal solution of it, while in Section 3. we present some applications of our theory.