Unconventional Superconductivity with a Sign Reversal in the Order Parameter of LaFeAsO(sub 1-x)Fx
NAVAL RESEARCH LAB WASHINGTON DC WASHINGTON United States
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We argue that the newly discovered superconductivity in a nearly magnetic, Fe-based layered compound is unconventional and mediated by antiferromagnetic spin fluctuations, though different from the usual super exchange and specific to this compound. This resulting state is an example of extended s-wave pairing with a sign reversal of the order parameter between different Fermi surface sheets. The main role of doping in this scenario is to lower the density of states and suppress the pair-breaking ferromagnetic fluctuations.