Universal Conductance Fluctuations in Disordered Metals

Abstract

Recently it has been found both experimentally^1–3 and theoretically^4–8 that the electrical conductance in disordered metals exhibits fluctuations as the magnetic field B or the chemical potential µ is varied. The RMS magnitude of these fluctuations for a given sample is the same as that from sample to sample and is of the order δG≈e²/h, independent of the degree of disorder, the sample size, spatial dimensions, provided the temperature is low enough that the inelastic scattering length L_in, is larger than any of the sample dimensions^5,7. L_in=(Dτ_in)^1/2 is the distance an electron diffuses during the inelastic scattering time τ_in if D is the diffusion constant. It is to be emphasized that such fluctuations are not time-dependent noise. Instead, the conductance G(µ, B) is a deterministic, albeit fluctuating function of its arguments, for a given realization of the impurity configuration.