Microscopic understanding of the orbital splitting and its tuning at oxide interfaces

TL;DR

This paper uses density functional theory and Wannier projections to identify the main causes of orbital splitting at oxide interfaces and demonstrates how to tune this splitting to control electronic properties.

Contribution

It reveals the primary mechanisms behind $t_{2g}$ orbital splitting and introduces a method for orbital engineering at oxide heterostructure interfaces.

Findings

Main source of $t_{2g}$ splitting identified as c-axis hopping and energy mismatch.

Orbital splitting can be tuned by designing specific heterostructures.

Enhanced control over interface electronic properties through orbital engineering.

Abstract

By means of a Wannier projection within the framework of density functional theory, we are able to identify the modified c-axis hopping and the energy mismatch between the cation bands as the main source of the $t_{2g}$ splitting around the $\Gamma$ point for oxide heterostructures, excluding previously proposed mechanisms such as Jahn-Teller distortions or electric field asymmetries. Interfacing LaAlO$_3$, LaVO$_3$, SrVO$_3$ and SrNbO$_3$ with SrTiO$_3$ we show how to tune this orbital splitting, designing heterostructures with more $d_{xy}$ electrons at the interface. Such an "orbital engineering" is the key for controlling the physical properties at the interface of oxide heterostructures.