Multiple Gaps and Superfluid Density from Interband Pairing in Iron Oxypnictides

We study a four-band model for the iron oxypnictides, in which the superconducting properties are assumed to be determined by the interband coupling between hole-like and electron-like Fermi sheets. We show that reasonable parameters can account for the angle-resolved photoemission spectra showing multiple gaps in Ba$_{1-x}$K$_x$Fe$_2$As$_2$, and for the temperature dependence of the superfluid density. At the same time, the zero-temperature value of the superfluid density shows a conventional scaling with the number of carriers.