Using density functional theory calculations, ultrathin films of ${\mathrm{SrVO}}_3(d^1)$ and ${\mathrm{SrCrO}}_3(d^2)$ on ${\mathrm{SrTiO}}_3$ substrates have been studied as possible multiferroics. Although both are metallic in the bulk limit, they are found to be insulating as a result of orbital ordering driven by lattice distortions at the ultrathin limit. While the distortions in ${\mathrm{SrVO}}_3$ have a first-order Jahn-Teller origin, those in ${\mathrm{SrCrO}}_3$ are ferroelectric in nature. This route to ferroelectricity results in polarizations comparable with conventional ferroelectrics.

• Received 1 February 2012

DOI:https://doi.org/10.1103/PhysRevLett.111.077601