Perspective-The Elusive Quantum Anomalous Hall Effect in MnBi₂Te₄: Materials

Observation of the quantum anomalous Hall effect (QAHE) in MnBi₂Te₄ flakes is one of the most exciting results in the study of the intrinsic magnetic topological insulator MnBi₂Te₄ and related compounds. Reproducing this fascinating result has been found to be challenging. The quality of starting MnBi₂Te₄ single crystals is believed to be the key factor. An interesting and important question to address is what is the right quality to enable the QAHE. In this perspective, we present possible approaches to tuning the magnetic and topological properties of MnBi₂Te₄ by using lattice imperfections, strain, stacking sequence, and interactions between the substrate and flakes/films. It is of critical importance to eventually identify the factor(s) responsible for the realization of QAHE.