A First-Principles Study of the Electronic Reconstructions of LaAlO3/SrTiO3 Heterointerfaces and Their Variants

TL;DR

This study uses first-principles calculations to explore the electronic structures of LaAlO3/SrTiO3 heterointerfaces, revealing the insulating-to-metallic transition, electron confinement mechanisms, and proposing tunable quantum well systems for oxide interface engineering.

Contribution

It introduces a comprehensive first-principles analysis of LaAlO3/SrTiO3 interfaces, including a new quantum well class and a unified model for thickness and field effects.

Findings

Insulating-to-metallic transition depends on LaAlO3 thickness.

Electrons are bound to n-type interface, holes diffuse away from p-type.

Proposed controllable quantum well systems based on polar catastrophe mechanism.

Abstract

We present a first-principles study of the electronic structures and properties of ideal (atomically sharp) LaAlO3/SrTiO3 (001) heterointerfaces and their variants such as a new class of quantum well systems. We demonstrate the insulating-to-metallic transition as a function of the LaAlO3 film thickness in these systems. After the phase transition, we find that conduction electrons are bound to the n-type interface while holes diffuse away from the p-type interface, and we explain this asymmetry in terms of a large hopping matrix element that is unique to the n-type interface. We build a tight-binding model based on these hopping matrix elements to illustrate how the conduction electron gas is bound to the n-type interface. Based on the `polar catastrophe' mechanism, we propose a new class of quantum wells at which we can manually control the spatial extent of the conduction electron gas. In addition, we develop a continuous model to unify the LaAlO3/SrTiO3 interfaces and quantum wells and predict the thickness dependence of sheet carrier densities of these systems. Finally, we study the external field effect on both LaAlO3/SrTiO3 interfaces and quantum well systems. Our systematic study of the electronic reconstruction of LaAlO3/SrTiO3 interfaces may serve as a guide to engineering transition metal oxide heterointerfaces.