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. 
Jing Yuan and Jiangping Hu
cond-mat.supr-con