Multiband electron-phonon coupling in the cuprates: Raman scattering and charge fluctuations

The role of multiband electron-phonon coupling for phonon Raman scattering and phonon-induced charge fluctuations in the high-$T_c$ cuprates is considered. Comparison of contributions from different bands to the phonon Raman vertex shows that the scattering intensity comes mainly from hole-phonon rather than from electron-phonon coupling and is very sensitive to doping. Interband electron-phonon coupling is as important for the phonon-induced charge fluctuations as electron-phonon coupling near the Fermi surface. The role of the latter increases near the Van Hove singularity in the electronic spectrum.