Coupling of electronic and structural degrees of freedom in vanadate superlattices

TL;DR

This study combines theoretical and experimental methods to understand how crystal and electronic structures interact in vanadate superlattices, enabling precise control of orbital properties through structural engineering.

Contribution

It provides a comprehensive analysis of the coupling between electronic and structural degrees of freedom in vanadate superlattices, highlighting how substrate orientation and layer thickness influence orbital polarization.

Findings

Density functional theory accurately predicts crystal structures.

Orbital degeneracy is lifted due to structural effects.

Substrate orientation and layer thickness can engineer orbital polarization.

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.