Universal Conductance Fluctuations
Encyclopedia
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
needs be larger than the momentum relaxation length 
. UCF is more profound when electrical transport is in weak localization
regime.
where 
, 
is the number of conduction channels and 
is the momentum relaxation length or mean free path. For weakly localized samples fluctuation in conductance is equal to fundamental conductance 
regardless of the number of channels.
Mesoscopic physics
Mesoscopic physics is a sub-discipline of condensed matter physics which deals with materials of an intermediate length scale. The scale of such materials can be described as being between the size of a quantity of atoms and of materials measuring micrometres. The lower limit can also be defined...
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
needs be larger than the momentum relaxation length . UCF is more profound when electrical transport is in weak localizationWeak localization
Weak localization is a physical effect which occurs in disordered electronic systems at very low temperatures. The effect manifests itself as a positive correction to the resistivity of a metal or semiconductor....
regime.
where , is the number of conduction channels and is the momentum relaxation length or mean free path. For weakly localized samples fluctuation in conductance is equal to fundamental conductance regardless of the number of channels.