Fundamental asymmetry in interfacial electronic reconstruction between insulating oxides

TL;DR

This study uses ab initio calculations to explore the electronic properties of LaAlO3/SrTiO3 interfaces, revealing an asymmetry in conductivity linked to atomic geometry and interfacial hopping effects, with implications for tuning oxide interface conductivities.

Contribution

It uncovers the atomic-geometry-driven asymmetry in interfacial electronic reconstruction between insulating oxides, explaining the origin of conductivity differences at specific interfaces.

Findings

Insulating-to-metallic transition occurs above a critical LaAlO3 thickness.

High conductivity is inherent to the TiO2/LaO interface due to atomic geometry.

Interfacial hopping causes bound electron states at the TiO2/LaO interface.

Abstract

We present an ab initio study of the (001) interfaces between two insulating perovskites, the polar LaAlO3 and the nonpolar SrTiO3. We observe an insulating-to-metallic transition above a critical LaAlO3 thickness. We explain that the high conductivity observed at the TiO2 /LaO interface and the lack of similar conductivity at the SrO/AlO2 interface are inherent in the atomic geometry of the system. A large interfacial hopping matrix element between cations causes the formation of a bound electron state at the TiO2 /LaO interface. This mechanism for the formation of interfacial bound states suggests a robust means for tuning conductivities at various oxide heterointerfaces.