Phonon Origin of High T c in Superconducting Cuprates

Eliashberg theory (ET), generalized for the account of the peculiar properties of the finite zone width electron-phonon (EP) systems with the non-constant electron density of states, the electron-hole nonequivalence, chemical potential renormalization with doping and frequency, and electron correlations in the vertex function, is used for the study of T _c in cuprates. The phonon contribution to the nodal anomalous electron Green function (GF) in cuprates is considered. The pairing on the full width of the electron zone was taken into account, not just on the Fermi surface. It is found that the finite zone width phenomenon in the newly derived Eliashberg equations for the finite zone width EP system together with the abrupt fall of the density of states above the Fermi surface are the crucial factors for the appearance of the high temperature superconductivity phenomenon. It is shown that near the optimal doping in the hole-doped cuprates high T _c value is reproduced with the EP interaction constant obtained from tunnel experiments.