Pairing symmetry in the iron-pnictide superconductor KFe ₂As ₂

The pairing symmetry is one of the major issues in the study of iron-based superconductors. We adopt a ten-orbital model by using the maximally localized Wannier functions based on the first-principles band structure calculations combined with the J ₁-J ₂ model for KFe ₂As ₂, the phase diagram of pairing symmetries is constructed. We find that the pairing symmetry for KFe ₂As ₂ is a nodal (sx2y ²+sx ²+y ²)-wave in the folded Brillouin zone with two iron atoms per unit cell. This pairing symmetry can explain the experiments observed nodes, and it also can be tested by future experiments.