Weak-disorder effects in the finite-charge infinite-U Hubbard model

Abstract

We calculate the effects of weak disorder on a strongly correlated electron system, namely a version of the infinite-U Hubbard model with general charge for which a 1/N expansion can be carried out (N being the orbital degeneracy). The partition function and quasiparticle decay rate are calculated to next leading order in the 1/N expansion by summing all ladder type diffusive corrections in the impurity potential. We find that away from the critical metal-insulator filling these quantities exhibit the power law behaviour expected on the basis of general weak-interacting theories. Very close to the metal-insulator filling, however, the situation changes and new, sublinear power law components are obtained. These new power laws are a result of the diffusion pole crossing over to a q4 behaviour, which is in turn a consequence of the 'holon' like propagation of the charge fluctuations in the pure system.