Effect of conduction electrons on the polarized Raman spectra of copper oxide superconductors.

The line shape, laser-wavelength dependence, coupling to phonons, and doping dependence of the Raman continua in YBa 2 Cu 3 O 7 single crystals differ for photons polarized parallel and perpendicular (ZZ geometry) to the Cu-O planes. The ZZ continuum in YBa 2 Cu 3 O 7 can be accurately fit to a formula that describes scattering by a «dirty» free electron gas with frequency-independent damping. The doping dependence of the ZZ continuum appears to be consistent with electronic scattering