Lattice Modes and Polarization Switching in Charge-Order-Driven Ferroelectrics

Charge ordering (CO) can occur in mixed-valence compounds when ordering of the charge states on different sites breaks symmetry and produce ferroelectricity. Several examples of charge-order driven ferroelectricity have been recently discussed, with experimental observations in magnetite Fe₃O₄ and first-principles predictions in systems including LuFe₂O₄, LaVO3/SrVO3 superlattices and LSFO. However, the switchability and precise mechanism of polarization switching in CO materials is still an open question. In this work, we use first-principles methods to investigate the ferroelectricity in SrVO₃-LaVO₃ superlattices, and demonstrate that the coupling of the charge order to the lattice has a crucial influence on the stabilities of various polar and nonpolar charge-ordered states. We discuss the application of this mechanism to explain the different electrical behaviors in LuFe₂O₄ and Fe₃O₄.