Metal-Insulator Transition and Jeff = 1/2 Spin-Orbit Insulating State in Rutile-based IrO2/TiO2 Superlattices

TL;DR

This study predicts a thickness-dependent metal-insulator transition in IrO2/TiO2 superlattices driven by spin-orbit coupling and electron correlations, resulting in a Jeff=1/2 insulating state in atomically-thin layers.

Contribution

It introduces rutile-based IrO2/TiO2 superlattices as new candidates for unconventional electronic states with a detailed theoretical prediction of their electronic phase behavior.

Findings

Predicted a metal-insulator transition controlled by IrO2 layer thickness.

Identified a Jeff=1/2 spin-orbit insulating state in atomically-thin IrO2 layers.

Highlighted the role of IrO6 octahedra connectivity in electronic properties.

Abstract

By combining 5d transition-metal oxides showing pronounced spin-orbit interactions and oxide-based heterostructures, we propose rutile-based IrO2/TiO2 superlattices as promising candidates for unconventional electronic properties. By means of density-functional-theory simulations complemented with Hubbard-like corrections, we focus on the evolution of the electronic structure as a function of the IrO2 layer thickness and predict the heterostructures to exhibit a thickness-controlled metal-to-insulator transition, crucially related to the connectivity among IrO6 octahedra. The subtle interplay between electron correlation and spin-orbit coupling leads to an almost pure Jeff = 1/2 spin-orbit insulating state at the level of atomically-thin IrO2 monolayer with almost isolated IrO6 octahedra, leading to a predicted emerging state awaiting for experimental confirmation.