Coupling of electronic and structural degrees of freedom in vanadate superlattices

Abstract

Heterostructuring provides different ways to manipulate the orbital degrees of freedom and to tailor orbital occupations in transition metal oxides. However, the reliable prediction of these modifications remains a challenge. Here, we present a detailed investigation of the relationship between the crystal and electronic structure in YVO$_3$-LaAlO$_3$ superlattices by combining ab initio theory, scanning transmission electron microscopy, and x-ray diffraction. Density functional theory simulations including an on-site Coulomb repulsion term, accurately predict the crystal structure and in conjunction with x-ray diffraction, provide an explanation for the lifting of degeneracy of the vanadium $d_{xz}$ and $d_{yz}$ orbitals, that was recently observed in this system. In addition, we unravel the combined effects of electronic confinement and octahedral connectivity by disentangling their impact from that of epitaxial strain. Our results demonstrate that the specific orientation of the substrate and the thickness of the YVO$_3$ slabs in the multilayer, can be utilized to reliably engineer orbital polarization.