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.