DRUDE WEIGHT AND DC CONDUCTIVITY OF CORRELATED ELECTRONS

The Drude weight D and the de conductivity sigma(dc)(T) of strongly co rrelated electrons are investigated theoretically. Analytic results ar e derived for the homogeneous phase of the Hubbard model at d = infini ty, and for spinless fermions in this limit with 1/d corrections syste matically included to lowest order. It is found that sigma(dc)(T) is f inite for all T > 0, displaying Fermi-liquid behavior, sigma(dc) propo rtional to 1/T-2, at low temperatures. The validity of this result for finite dimensions is examined by investigating the importance of umkl app scattering processes and vertex corrections. A finite dc conductiv ity for T > 0 is argued to be a generic feature of correlated lattice electrons in not too low dimension.