WAVE-PACKET APPROACH TO NOISE IN MULTICHANNEL MESOSCOPIC SYSTEMS

Noise in conductors transmitting electrons coherently between attached reservoirs is calculated by following wave packets incident on the sample. The Pauli principle restricts the occupation of wave packets, spreading electrons more uniformly among the available packets, and thus reducing the noise below that of the classical shot-noise expression for totally uncorrelated electrons. After a brief review of the results for one-dimensional leads, we treat the case of the sample attached to two multichannel leads. A proper choice of basis for the wave packets permits this case to be reduced to that of a set of independent parallel one-channel samples. This picture is extended to the case of excess noise in multiterminal samples at zero temperature, leading to anticorrelated fluctuations between different leads. The anticorrelated fluctuations are analyzed, in particular detail for a Y-shaped three-lead sample. Our wave-packet approach is presented as a physically intuitive alternative to the existing approaches to mesoscopic noise, and leads to identical results.