A phenomenological multiband Eliashberg model for LiFeAs.

The phenomenology of a LiFeAs superconductor can be explained in the framework of four-band s±-wave Eliashberg theory. We have examined the experimental data available in the literature and we have found that it is possible to reproduce the experimental critical temperature, the gap values and the upper critical magnetic field within an effective model in a moderately strong coupling regime that must include both an intraband term λ11 ∼ 0.9 and an interband spin-fluctuation ([Formula: see text]) coupling. The presence of a nonnegligible intraband coupling can be a fictitious effect of the violation of Migdal's theorem.