Feedback Effect in Iron Pnictide Superconductors

The experimental data of four iron-pnictides superconductors: LaFeAsO1−xFx, Ba1−xKxFe2As2, SmFeAs O1−xFx , and Ba(FexCo1−x )2As2 have been examined and explained in the framework of a three bands s± wave Eliashberg theory with only two free parameters plus a feedback effect, i.e., the effect of the condensate on the antiferromagnetic spin fluctuations responsible of the superconductivity in these compounds. From the theory, it is possible to obtain the values of critical temperature, superconductive gaps, upper critical field, etc. in very good agreement with experimental data in a moderate strong-coupling regime: λtot ≈ 2.4–2.8.