Coupled nonpolar-polar metal-insulator transition in 1:1 SrCrO${}_3$/SrTiO${}_3$ superlattices: A first-principles study

Using first principles calculations, we determined the epitaxial-strain dependence of the ground state of the 1:1 SrCrO${}_3$/SrTiO${}_3$ superlattice. The superlattice layering leads to significant changes in the electronic states near the Fermi level, derived from Cr $t_{2g}$ orbitals. An insulating phase is found when the tensile strain is greater than 2.2% relative to unstrained cubic SrTiO${}_3$. The insulating character is shown to arise from Cr $t_{2g}$ orbital ordering, which is produced by an in-plane polar distortion that couples to the superlattice d-bands and is stabilized by epitaxial strain. This effect can be used to engineer the band structure near the Fermi level in transition metal oxide superlattices.