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 $s\pm$ 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 interaction parameters are essential to make FRG an useful method to determine the leading channel of superconducting instability.

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