Plasmons and phonons in anisotropic systems and their effect on high-Tc superconductivity

The structure of the plasmon and phonon bands in conducting, highly anisotropic layered materials is studied. The observed high superconducting transition temperatures are caused, in our view, by the coexistence of strong electronphonon coupling and the plasmon mechanism. A generalized Eliashberg equation describing the effects of phonons and plasmons on the pairing is presented. Our approach is based on the method of thermodynamic Green's functions. We point out connections to experiments and briefly comment on other models.