Charge-Order-Induced Ferroelectricity in LaVO3/SrVO3 Superlattices

In this paper, the structure and properties of the $1:1$ superlattice of ${LaVO}_3$ and ${SrVO}_3$ are investigated with a first-principles density-functional-theory-plus-$U$ ($DFT+U$) method. The lowest energy states are antiferromagnetic charge-ordered Mott-insulating phases. In one of these insulating phases, layered charge ordering combines with the layered La/Sr cation ordering to produce a polar structure with a large nonzero spontaneous polarization normal to the interfaces. This polarization, comparable to that of conventional ferroelectrics, is produced by electron transfer between the $V^{3+}$ and $V^{4+}$ layers. The energy of this normal-polarization state relative to the ground state is only 3 meV per vanadium. Under tensile strain, this energy difference can be further reduced, suggesting that the normal-polarization state can be induced by an electric field applied normal to the superlattice layers, yielding an antiferroelectric double-hysteresis loop. Finally, if the system does not switch back to the ground state on removal of the field, a ferroelectric-type hysteresis loop could be observed.