Intrinsic large gap quantum anomalous Hall insulators in La$X$ ($X$=Br, Cl, I)

TL;DR

This paper predicts a new class of intrinsic quantum anomalous Hall insulators in LaX (X=Br, Cl, I) with sizable band gaps, ferromagnetic order, and potential for experimental realization and strain engineering.

Contribution

It introduces a theoretical prediction of intrinsic QAH insulators in LaX compounds, highlighting their ferromagnetism, large band gaps, and strain tunability, which are novel features.

Findings

LaX compounds are innate ferromagnets that become QAH insulators due to spin-orbit coupling.

The band gap can reach up to 25 meV, tunable above 75 meV with strain.

Integer Chern numbers are confirmed via Berry phase calculations.

Abstract

We report a theoretical prediction of a new class of bulk and intrinsic quantum Anomalous Hall (QAH) insulators La$X$ ($X$=Br, Cl, and I) via relativistic first-principle calculations. We find that these systems are innate long-ranged ferromagnets which, with the help of intrinsic spin-orbit coupling, become QAH insulators. A low-energy multiband tight binding model is developed to understand the origin of the QAH effect. Finally integer Chern number is obtained via Berry phase computation for each two-dimensional plane. These materials have the added benefit of a sizable band gap of as large as $\sim$ 25 meV, with the flexibility of enhancing it to above 75 meV via strain engineering. The synthesis of La$X$ materials will provide the impurity-free single crystals and thin-film QAH insulators for versatile experiments and functionalities.