Multiple gaps and superfluid density from interband pairing in a four-band model of the 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 holelike and electronlike Fermi sheets. We show that reasonable parameters can account for the angle-resolved photoemission spectra, showing multiple gaps in ${\text{Ba}}_{1-x}{\text{K}}_x{\text{Fe}}_2{\text{As}}_2$, 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.

Figure 1

(Color online) Schematic of the multiband model used in this work. The two hole bands $\alpha$ and $\beta$ are centered around the $\Gamma$ point while the electron $\gamma$ bands are centered around the $M$ point.

Figure 2

(Color online) (a) Temperature dependence of the SC gaps in the hole and electron bands. The parameter values are optimized to obtain the same gap value in the $\alpha$ and $\gamma$ bands (see the text). Moreover, we used $\lambda =\Lambda /2$ to have ${\Delta }_{\beta }={\Delta }_{\alpha }/2$. (b) SC gaps for the hopping parameters estimated from ARPES measurements of Ref. 7 at half filling.

Figure 3

(Color online) Temperature dependence of the superfluid density in units of Eq. (6) for the various bands.