On existence of quantum diffusion of 2-D electrons at the surface

A quantum diffusion of 2-D electrons at a metal substrate has been shown to arise because of surface-bulk interaction via hybridization provided that the surface Fermi momentum has been smaller than the bulk one. The diffusion coefficient D has been found to depend nonmonotonously on sample dimensions L. An initial decrease in D has turned into an increase for sufficiently large L. The minimum in D has nonanalytically depended on the hybridization constant: D _min∼g ^{4}/{3}. The effects predicted have resulted from the instability of the zero-component nonlinear σ-model with respect to inclusion of certain symmetry — breaking terms which have proved to increase under RG transformations.