Two-time Green's functions in superconductivity theory
In this paper there are derived superconductivity equations for both the general fermion-boson model and the Hubbard model with strong Coulomb correlation. This is done by differentiating the Green's functions in order to derive a Dyson-type equation, which is solved in the approximation of noncrossing diagrams for the self-energy operator. The theory incorporates the method of the equations of motion for two-time thermodynamic Green's functions, which allows the author to obtain strong-coupling equations of the Migdal-Eliashberg-type for calculating the self-energy operator in the approximation of noncrossing diagrams. The solution of the self-consistent system of equations in the strong-coupling approximation of the Hubbard model given in this paper allows concluding that the superconducting \(d\)-wave pairing with a high critical temperature is optimal.
scientific article; zbMATH DE number 5346149