A light-scattering study of dynamical carrier properties in cuprate systems

Results of inelastic light-scattering experiments are analysed in terms of a memory function M(ω) = ωλ(ω)+iΓ(ω). Using this approach dynamical scattering rates Γ(ω) = 1/τ(ω) and mass-enhancement factors 1 + λ(ω) = m*(ω)/m for the carriers are derived as a function of temperature T and doping p. The obtained quantities are in qualitative agreement with results from infrared spectroscopy and longitudinal transport. In addition, Raman scattering reveals new information about the anisotropy of the carrier properties. The anisotropy increases substantially towards lower doping when the influence of electronic correlations gain importance. The analysis turns out to be very useful for the understanding of the pseudogap in the normal state