Impurity suppression of the critical temperature in the iron-based superconductors
We study the impurity suppression of the critical temperature Tc of the FeAs superconductors theoretically based on the the ±s-wave pairing state of a two band model. The effects of non-magnetic and magnetic impurities are studied with theT -matrix approximation, which can continuously treat impurity scattering from weak to strong coupling limit. We found that both magnetic and non-magnetic impurities suppress Tc with a rate that is practically indistinguishable from the standard d-wave case despite a possibly large difference of the positive and negative s-wave order parameter (OP) magnitudes. This is because the density of states enters together with the OP magnitude for the scattering process.