Electronic properties of superconducting FeS

We report first-principles density-functional theory results on the electronic and magnetic properties of the recently discovered superconducting FeS, which reveals important differences with the other members of the iron-chalcogenides (FeSe and FeTe). The band structure of FeS is characterized by two hole bands at the Fermi energy with a fully occupied dxy band at Γ. A stripe-antiferromagnetic phase with a small magnetic moment is the most stable magnetic solution, but different magnetic phases have comparable energies indicating a tight competition. Including local interactions treated within dynamical mean-field theory, we find significant correlation effects with orbital-dependent strength and character, even if all the fingerprints of correlations are slightly weaker than in FeSe. The study of the effect of pressure reveals significant changes in the electronic structure of the material and of the correlation effects. These results point toward further studies on the possible superconducting phase stabilized by pressure effects or two dimensionality, in analogy with pressurized and monolayer FeSe.