Universal conductance fluctuations

Diffusion modes and conductance fluctuations

During the last 10–15 years study of transport through very small conductors has been a very popular topic of both theoretical and experimental research (for reviews see, e.g., Altshuler, Lee, and Webb (1991); Kirk and Reed (1992); Beenakker and van Houten (1991)). These systems are much larger (typically of the size 100–000 Å) than atomic distances, and, naturally, they cannot be considered as microscopic objects. Then, what can be special in their properties with respect to properties of macroscopic conductors? The answer is related to the quantum interference that proved to be so crucial to the localization problem. Although the conductors may contain internal defects, such disorder does not destroy the coherence of the wave functions and quantum effects can become very important, leading to completely new physical phenomena. The last two chapters were devoted to study of some exotic effects in isolated or almost isolated samples.

The quantum effects in isolated metal particles can be destroyed by inelastic scattering only. It is only at the classical limit that both elastic and inelastic scattering play equivalent roles in transport. Considering inelastic processes one should distinguish between the cases lϕ < L and lϕ > L, where lϕ is the inelastic mean free path and L is the size of the sample.