From Hunds insulator to Fermi liquid: Optical spectroscopy study of K doping in BaMn$_2$As$_2$

We present optical transmission measurements that reveal a charge gap of 0.86 eV in the local moment antiferromagnetic insulator BaMn$_2$As$_2$, an order of magnitude larger than previously reported. Density functional theory plus dynamical mean field theory (DFT+DMFT) calculations correctly reproduce this charge gap only when a strong Hund's coupling is considered. Thus, BaMn$_2$As$_2$ is a member of a wider class of Mn pnictide compounds that are Mott-Hund's insulators. We also present optical reflectance for metallic 2% K doped BaMn$_2$As$_2$ that we use to extract the optical conductivity at different temperatures. The optical conductivity $σ_1$($ω$) exhibits a metallic response that is well described by a simple Drude term. Both $σ$($ω$$\rightarrow$0, T) and $ρ$(T) exhibit Fermi liquid temperature dependencies. From these measurements, we argue that a more strongly correlated Hund's metal version of the parent compounds of the iron pnictide superconductors has not yet been realized by doping this class of Hund's insulators.

No reviews yet.

No comments yet.