ON THE THEORY OF 2D SUPERCONDUCTIVITY AT ARBITRARY DENSITY OF FERMIONS AND INDIRECT INTERACTION BETWEEN THEM

Using the microscopic model Hamiltonian, the equations for order param eter and chemical potential have been obtained for a system of Fermi-p articles interacting with phonons which permit an analysis of its supe rconducting properties to be made for an arbitrary fermion concentrati on. The solution of the equations is given that makes it possible to t race the crossover from a local pair regime to Cooper pairing. The typ e of superconducting behavior is shown to depend on both the position of the Fermi level with respect to a maximum phonon energy and strengt h of indirect interactions between fermions.