Effective three-band structure in Fe-based superconductors

We present self-consistent calculations of the multi-gap structure measured in some Fe-based superconductors. These materials are known to have structural disorder in real space and a multi-gap structure due to the $3d$ Fe-orbitals contributing to a complex Fermi surface topology with hole and electron pockets. Different experiments identify three s-wave like superconducting gaps with a single critical temperature ($T_c$). We investigate the temperature dependence of these gaps by a multi-band Bogoliubov-deGennes theory at different pockets in the presence of effective hybridizations between some bands and an attractive temperature dependent intra-band interaction. We show that this approach reproduces the three observed gaps and single $T_c$ in different compounds of Ba$_{1-x}$K$_{x}$Fe$_2$As$_2$, providing some insights on the inter-band interactions.

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