Drude weight and dc conductivity of correlated electrons

The Drude weight D and the dc conductivity ${\mathrm{\sigma }}_{\mathrm{dc}}$(T) of strongly correlated electrons are investigated theoretically. Analytic results are derived for the homogeneous phase of the Hubbard model at d=∞, and for spinless fermions in this limit with 1/d corrections systematically included to lowest order. It is found that ${\mathrm{\sigma }}_{\mathrm{dc}}$(T) is finite for all T>0, displaying Fermi-liquid behavior, ${\mathrm{\sigma }}_{\mathrm{dc}}$∝1/${\mathit{T}}^2$, at low temperatures. The validity of this result for finite dimensions is examined by investigating the importance of umklapp scattering processes and vertex corrections. A finite dc conductivity for T>0 is argued to be a generic feature of correlated lattice electrons in not too low dimensions.