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

TL;DR

This study uses first-principles calculations to explore how epitaxial strain influences the electronic and structural phases of SrCrO$_3$/SrTiO$_3$ superlattices, revealing strain-induced insulator transitions driven by orbital ordering.

Contribution

It demonstrates the strain-dependent transition to an insulating phase in SrCrO$_3$/SrTiO$_3$ superlattices caused by polar distortions and orbital ordering, providing insights for band structure engineering.

Findings

Insulating phase occurs at >2.2% tensile strain.

Cr $t_{2g}$ orbital ordering drives the insulating state.

Epitaxial strain stabilizes in-plane polar distortions.

Abstract

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.