Comment on Mott's localization criterion for disordered systems

Abstract

We investigate the validity of Mott's localization criterion originally applied by him when a pseudogap opens. Values of the ratio η(E_C ) of the perturbed to the unperturbed density of states at the mobility edges are obtained via approxi mate numerical calculations. They suggest that η, while slowly varying with disorder, is a function of the kind of disorder, the probability distribution of the disorder and the kind of mobility edge, exterior or interior to the band. The value of η for the interior mobility edges is found to be approximately 2/3 rather than 1/3. The value of η approaches 1/3 as the exterior mobility edge approaches the band edge, when the density of states become free-electron like and η becomes equi valent to Mott's g. The product of the transfer integral for nearest neighbours with the density of states at the mobility edge is found to be practically constant for the interior mobility edges.