High-temperature superconductivity in two-band materials with interband pairing

The Eliashberg theory generalized using peculiar properties of two-band electron–phonon (EP) systems is employed for studying T_c in two-band materials (in particular, pnictides). In view of probably strong EP coupling, we take into account pairing within the entire width of the electron band, not only in a narrow layer at the Fermi surface. It is found that the effect of pairing of electrons belonging to different bands is a decisive factor for manifestation of the effect of high T_c in these materials. It is shown that in materials analogous to pnictides, high T_c values are reproduced by the two-band spectral function of electron–phonon interaction. The existence of one more family of two-band high-temperature materials with a superconducting transition temperature T_c comparable to that in cuprates is predicted