Transport of local pairs in metallic oxides: Calculation of the frequency and temperature dependence of the conductivity

A model of the electronic structure of metal-oxide compounds is applied to the calculation of the oxide conductivity above the superconducting transition. The model takes into account both localized pairs of electrons or holes and itinerant (delocalized) electrons or holes. The magnitude of the estimated conductivity is in accord with experimental results and behaves as a function of temperature as T-2 or T-1 depending on the assumption of weak or strong correlation between the pair occupation fluctuations at different lattice sites. The cutoff frequency for pair conductivity scales linearly with temperature. This compares favorably with a Drude-model analysis of experimental results for the optical conductivity in terms of a scattering rate with linear T dependence