A phenomenological multiband Eliashberg model for LiFeAs

TL;DR

This paper develops a four-band Eliashberg model to explain the superconducting properties of LiFeAs, successfully reproducing experimental data by considering both intraband and interband couplings in a moderate strong-coupling regime.

Contribution

It introduces a phenomenological multiband Eliashberg model for LiFeAs that accounts for intraband and interband couplings, aligning theoretical predictions with experimental observations.

Findings

Reproduces critical temperature and gap values

Identifies significant intraband and interband couplings

Suggests intraband effects may be due to Migdal's theorem violation

Abstract

The phenomenology of LiFeAs superconductor can be explained in the framework of a four-band s$\pm$-wave Eliashberg theory. We have examined the experimental data available in literature and we have found out that it is possible to reproduce the experimental critical temperature, the gap values and the upper critical magnetic field within an effective model in moderate strong-coupling regime that must include both an intraband term $\lambda_{11}\sim0.9$ and an interband spin-fluctuations ($\lambda_{tot}^{sf}\sim1.5$) coupling. The presence of a non negligible intraband coupling can be a fictitious effect of the violation of Migdal's Theorem.