RANDOM POTENTIAL INFLUENCE ON PHONON RAMAN-SCATTERING IN HIGH-TEMPERATURE SUPERCONDUCTORS

Raman scattering in high-temperature superconductors is considered, assuming the presence of a random potential caused by either crystal non-stoichiometry or oxygen disorder. The renormalization of the electron-phonon interaction by impurity scattering for phonons of different symmetry has been analyzed. The analysis has been extended so as to take into consideration the finite wavevector phonons. On the basis of the theory developed, unusual properties of phonon Raman scattering in the high-temperature superconductors are qualitatively considered. They include the phonon line-shape and its dependence on the scattering polarizations and resonant conditions, and non-Bose temperature dependence of a number of Raman active phonons.