Electronic correlations in the ferroelectric metallic state of LiOsO3

LiOsO3 has been recently identified as the first unambiguous "ferroelectric metal," experimentally realizing a prediction by Anderson and Blount [Phys. Rev. Lett. 14, 217 (1965)]. In this Rapid Communication, we investigate the metallic state in LiOsO3 by means of infrared spectroscopy supplemented by density functional theory and dynamical mean-field theory calculations. Our measurements and theoretical calculations clearly show that LiOsO3 is a very bad metal with a small quasiparticle weight, close to a Mott-Hubbard localization transition. The agreement between experiments and theory allows us to ascribe all the relevant features in the optical conductivity to strong electron-electron correlations within the t(2g) manifold of the osmium atoms.