Unconventional superconductivity with a sign reversal in the order parameter of LaFeAsO1-xFx

Phys Rev Lett. 2008 Aug 1;101(5):057003. doi: 10.1103/PhysRevLett.101.057003. Epub 2008 Jul 29.


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 superexchange 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.