Five gaps Eliashberg model for KCa2Fe4As4F2: relevance of the electronic band

Experimental data from the recently discovered iron-based superconductor (IBS) KCaFeAsF is analyzed within a realistic five-band Eliashberg model with coupling provided by antiferromagnetic spin fluctuations. Fundamental parameters are deduced from available angle resolved photoemission spectoscopy (ARPES) and ab-initio density functional theory (DFT) data, and several physical properties are calculated: critical temperature, upper critical field, gap values, resistivity and superfluid density. This procedure, usually extremely successful in IBSs, highlights the peculiar behavior of this new compound in which s and d -wave character might coexist and where the electron band is close to vanish.