Two-particle Green functions of itinerant electrons with Heisenberg magnetic interaction

The equation in the ladder approximation was derived for the two-particle Green function of the itinerant electrons with the Heisenberg ferromagnetic and antiferromagnetic interaction. The general form of its solution was found. The existence of the pole in this solution is related to the condensation of the bound pairs in the corresponding spin state. The condition for the pole determines the critical temperature Tc. The effective interaction between the mobile holes due to the mobile hole - localized spin coupling in the two-band Hubbard model was also studied. (author). 32 refs