Funtional Renormalization Group Study of the Pairing Symmetry and   Pairing Mechanism of the FeAs Based High Temperature Superconductors
  We apply the fermion functional renormalization group method to determine the pairing symmetry and pairing mechanism of the FeAs-Based materials. Within a five band model with pure repulsive interactions, we find an electronic-driven superconducting pairing instability. For the doping and interaction parameters we have examined, extended s-wave, whose order parameter takes on opposite sign on the electron and hole pockets, is always the most favorable pairing symmetry. The pairing mechanism is the inter Fermi surface Josephson scattering generated by the antiferromagnetic correlation. 
Fa Wang, Hui Zhai, Ying Ran, Ashvin Vishwanath and Dung-Hai Lee