Interface engineering of quantum Hall effects in digital transition metal oxide heterostructures

TL;DR

This paper predicts that bilayers of transition-metal oxides grown along the [111] axis can be engineered to exhibit topological insulator properties, with tunable band structures and potential for room-temperature quantum spin-Hall effects.

Contribution

It introduces a new class of two-dimensional topological insulators based on perovskite-type transition-metal oxide bilayers, with detailed predictions of their electronic properties.

Findings

LaAuO₃ bilayers have a topologically nontrivial gap of 0.15 eV.

Band topology can be tuned via doping, substrates, and gate voltages.

Potential realization of quantum spin-Hall effect at room temperature.

Abstract

Topological insulators are characterized by a nontrivial band topology driven by the spin-orbit coupling. To fully explore the fundamental science and application of topological insulators, material realization is indispensable. Here we predict, based on tight-binding modeling and first-principles calculations, that bilayers of perovskite-type transition-metal oxides grown along the [111] crystallographic axis are potential candidates for two-dimensional topological insulators. The topological band structure of these materials can be fine-tuned by changing dopant ions, substrates, and external gate voltages. We predict that LaAuO$_3$ bilayers have a topologically-nontrivial energy gap of about 0.15 eV, which is sufficiently large to realize the quantum spin-Hall effect at room temperature. Intriguing phenomena, such as fractional quantum Hall effect, associated with the nearly-flat topologically-nontrivial bands found in $e_g$ systems are also discussed.