Universal conductance fluctuations

Universal conductance fluctuations (UCF) in quantum physics is a phenomenon encountered in electrical transport experiments in mesoscopic species. The measured electrical conductance will vary from sample to sample, mainly due to inhomogeneous scattering sites. Fluctuations originate from coherence effects for electronic wavefunctions and thus the phase-coherence length l ϕ needs be larger than the momentum relaxation length l m . UCF is more profound when electrical transport is in weak localization regime. l ϕ < l c where l c = M ⋅ l m , M is the number of conduction channels and l m is the momentum relaxation due to phonon scattering events length or mean free path. For weakly localized samples fluctuation in conductance is equal to fundamental conductance G o = 2 e 2 / h regardless of the number of channels.