Evidence for Jahn-Teller-driven metal-insulator transition in strained SrCrO3 from first principles calculations

TL;DR

This study uses first-principles calculations to propose that strain induces a Jahn-Teller distortion in SrCrO3, leading to a metal-insulator transition by lifting orbital degeneracy.

Contribution

It demonstrates that tensile strain can trigger a Jahn-Teller distortion in SrCrO3, providing a microscopic mechanism for the strain-induced metal-insulator transition.

Findings

Unstrained SrCrO3 is close to Jahn-Teller instability.

Tensile strain lowers the energy of the d_xy band.

Jahn-Teller distortion opens an electronic band gap.

Abstract

Using density-functional theory (DFT) and its extension to DFT+$U$, we propose a possible scenario for a strain-induced metal-insulator transition which has been reported recently in thin films of SrCrO$_3$. The metal-insulator transition involves the emergence of a Jahn-Teller (JT) distortion similar to the case of the related rare-earth vanadates, which also exhibit a nominal $d^2$ occupation of the transition metal cation. Our calculations indicate that, for realistic values of the Hubbard $U$ parameter, the unstrained system exhibts a C-type antiferromagnetically ordered ground state, that is already rather close to a JT instability. However, the emergence of the JT distortion is disfavored by the large energetic overlap of the $d_{xz}$/$d_{yz}$ band with the lower lying $d_{xy}$ band. Tensile epitaxial strain lowers the energy of the $d_{xy}$ band relative to $d_{xz}$/$d_{yz}$ and thus brings the system closer to the nominal filling of $d_{xy}^1(d_{xz}d_{yz})^1$. The JT distortion then lifts the degeneracy between the $d_{xz}$ and $d_{yz}$ orbitals and thus allows to open up a gap in the electronic band structure.