# Abstract:

We apply the fermion functional renormalization group method to study the pairing symmetry and pairing mechanism of the iron-based
superconductors. Using realistic tight-binding model of Fe d-orbitals fitted to band structure calculations and natural local interactions, we
find an electronic-driven superconducting pairing instability. For the doping and interaction parameters we have examined, extended s-wave($s \pm$) pairing, whose order parameter takes on opposite sign on the electron and hole Fermi surfaces, is always the most favorable pairing
symmetry. The pairing mechanism is the inter-Fermi-surface pair scattering generated by the antiferromagnetic correlation.
We will also briefly discuss methods to detect this unconventional
pairing.

References:
FW, Hui Zhai, Ying Ran, Ashvin Vishwanath, Dung-Hai Lee, Phys. Rev. Lett. 102, 047005 (2009);
FW, Hui Zhai, Dung-Hai Lee, Europhysics Letters 85, 37005 (2009);
Hui Zhai, FW, Dung-Hai Lee, Phys. Rev. B 80, 064517 (2009);
Pouyan Ghaemi, FW, Ashvin Vishwanath, Phys. Rev. Lett. 102, 157002 (2009)

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