Title: Thermodynamic Green functions in theory of superconductivity
Author(s):

N.M.Plakida (Joint Institute for Nuclear Research, 141980 Dubna, Russia)

A general theory of superconductivity is formulated within the thermodynamic Green function method for various types of pairing mediated by phonons, spin fluctuations, and strong Coulomb correlations in the Hubbard and t-J models. A rigorous Dyson equation for matrix Green functions is derived in terms of a self-energy as a many-particle Green function. By applying the noncrossing approximation for the self-energy, a closed self-consistent system of equations is obtained, similar to the conventional Eliashberg equations. A brief discussion of superconductivity mediated by kinematic interaction with an estimation of a superconducting transition temperature in the Hubbard model is given.

Key words: sGreen functions, theory of superconductivity, strong electron correlations

PACS: 74.20.-z, 74.20.Mn, 74.72.-h