Abstract
We present optical transmission measurements that reveal a charge gap of 0.86 eV in the local-moment antiferromagnetic insulator , an order of magnitude larger than previously reported. Density functional theory plus dynamical mean-field theory () calculations correctly reproduce this charge gap only when a strong Hund's coupling is considered. Thus, is a member of a wider class of Mn pnictide compounds that are Mott–Hund insulators. We also present optical reflectance for metallic 2%-K-doped that we use to extract the optical conductivity at different temperatures. The optical conductivity exhibits a metallic response that is well described by a simple Drude term. Both and exhibit Fermi-liquid temperature dependencies. From these measurements, we argue that a more strongly correlated Hund-metal version of the parent compounds of the iron pnictide superconductors has not yet been realized by doping this class of Hund insulators.
- Received 31 May 2015
DOI:https://doi.org/10.1103/PhysRevB.92.115142
©2015 American Physical Society