Multiple Bands - A Key to High - Temperature Superconductivity in Iron Arsenides?

In the framework of four-band model of superconductivity in iron arsenides proposed by Barzykin and Gor'kov we analyze the gap ratios on hole - like and electron - like Fermi - surface cylinders. It is shown that experimentally observed (ARPES) gap ratios can be obtained only within rather strict limits on the values of pairing coupling constants. The difference of T_c values in 1111 and 122 systems is reasonably explained by the relative values of partial densities of states. The multiple bands electronic structure of these systems leads to a significant enhancement of effective pairing coupling constant determining T_c, so that high enough T_c values can be achieved even for the case of rather small intraband and interband pairing interactions.