Design of a Mott Multiferroic from a Nonmagnetic Polar Metal

We examine the electronic properties of the newly discovered ``ferroelectric metal'' LiOsO₃ combining density-functional and dynamical mean-field theories. We show that the material is close to a Mott transition and that electronic correlations can be tuned to engineer a Mott multiferroic state in the $1/1$ superlattice of LiOsO₃ and LiNbO₃. We use electronic structure calculations to predict that the (LiOsO₃)₁/(LiNbO₃)₁ superlattice exhibits strong coupling between magnetic and ferroelectric degrees of freedom with a ferroelectric polarization of 41.2 μC cm^-2, Curie temperature of 927 K, and N\'eel temperature of 379 K. Our results support a route towards high-temperature multiferroics, i.e., driving nonmagnetic polar metals into correlated insulating magnetic states.