OPTICAL AND DC CONDUCTIVITIES IN HIGH-T-C SUPERCONDUCTORS - SPIN-FLUCTUATION SCATTERING IN THE EMERY MODEL

On the basis of the Emery model for the CuO2 plane, the optical conduc tivity and resistivity due to the inelastic scattering of oxygen holes by antiferromagnetic fluctuations of copper spins are calculated. For moderate hole doping, the electrical conductivity obeys a generalized Drude law. Using a phenomenological model for the dynamic spin suscep tibility, the in-plane resistivity reveals a crossover from a quadrati c to a linear temperature dependence at the scale of the spin-fluctuat ion energy. The frequency dependence of the scattering rate changes fr om a quadratic to a linear increase over a wide frequency range. The t heory is compared with experiments on LSCO and YBCO compounds, where t he spin dynamics is described within the model by Millis et al. A good quantitative agreement (in particular of the frequency-dependent scat tering rate) with experiments is found. We conclude that the spin-fluc tuation scattering may play a dominant role in the transport propertie s of Cu-oxide superconductors.