Relationship between pairing symmetries and interaction parameters in iron-based superconductors from functional renormalization group calculations

Pairing symmetries of iron-based superconductors are investigated systematically in a five-orbital model within the different regions of interaction parameters by functional renormalization group (FRG). Even for a fixed Fermi surface with both hole and electron pockets, it is found that depending on interaction parameters, a variety of pairing symmetries, including two types of d-wave and two types of s-wave pairing symmetries, can emerge. Only the $d_{x^2-y^2}$- and the s±-waves are robustly supported by the nearest-neighbor (NN) intra-orbital J ₁ and the next-nearest-neighbor (NNN) intra-orbital J ₂ antiferromagnetic (AFM) exchange couplings, respectively. This study suggests that the accurate initial input of the interaction parameters is essential to make FRG a useful method to determine the leading channel of superconducting instability. (letter)