Orbital selective Mott physics in the 111 iron pnictides

Motivated by recent ARPES measurements on the iron pnictides compounds $A$FeAs ($A$=Li,Na), we study the effects of electron correlations on the bandstructures in these compounds via microscopic multiorbital Hubbard models using the U(1) slave-spin theory. We find that the calculated phase diagrams of both compounds at the commensurate filling $n=6$ contain a common orbital selective Mott phase (OSMP) besides a metallic one and a Mott insulating one. The OSMP is stabilized in a much wider parameter range in LiFeAs than in NaFeAs, as a consequence of a larger energy splitting between the Fe $d_{xy}$ orbital and the $d_{xz/yz}$ orbitals, as well as suppressed hoppings between the $d_{xy}$ and $d_{xz/yz}$ orbitals in LiFeAs. Meanwhile, the onset Coulomb coupling for the orbital selective Mott transition (OSMT) in LiFeAs shows a strong temperature dependence. This pushes the LiFeAs system close to an OSMT with a strongly suppressed quasiparticle spectral weight in the $d_{xy}$ orbital at high temperatures, similar to the iron chalcogenides. Our finding indicates that the orbital selective Mott physics is a common feature for both iron pnictides and iron chalcogenides.