Self-consistent theory of Anderson localization of two-dimensional non-interacting electrons is formulated in the context of the exact transport equation and conductivity expression derived by the present authors (YI). The irreducible scattering vertex by Vollhardt and Wölfle (VW) is used in this equation, determining the diffusion coefficient in the scattering vertex self-consistently, through Einstein relation. It predicts a similar localization length to that obtained by VW, but shows that the conductivity evaluated by the Kubo formula decays exponentially, as the system size approaches the localization length. The result is opposed to the prediction by VW, who showed different behaviour of the diffusion coefficient that is equivalent to our conductivity. Our calculation also implies that the localization may be described along with the Landau-Silin theory of Fermi liquid.
Subject Index: 350Earlier microscopic studies of Anderson localization of non-interacting electrons, following the scaling theory by Abrahams et al., 1) have shown an overall agreement with this phenomenological theory. 2)-7) Among others, Vollhardt and Wölfle (VW) have developed a self-consistent theory that covers from weakly to strongly localized regimes, taking into account the hydrodynamic singularity which is determined by the diffusion coefficient in question. 5)-7) The main conclusions of this theory are now widely accepted. A point which may be further questioned is that for d = 2, where d is the dimensionality, it does not predict the exponential decay of the diffusion coefficient, as a function of the system size in the vicinity of the localization length. The point has been criticized by Suslov very recently. 9)We investigate the matter in the light of the exact transport equation and the associated conductivity expression derived by the present authors. 10) Avoiding the ultraviolet divergence in the conventional expression, we formulate the problem in such a way to maintain a rigid self-consistency between the diffusion coefficient and the scattering vertex. We work on the conductivity, which is the main difference from the previous authors who work basically on the resistivity. The exponential decay of the conductivity results naturally in our formalism. We regard the diffusion coefficient of a finite system as equivalent to the conductivity given by the Kubo formula, in view of the Einstein relation. The argument is therefore different than that by Suslov. Also, our treatment shows a clear correspondence to the phenomenological Fermi liquid theory, which allows for a classical view of quantum transport, including localization.