Experimental Realization of an Intrinsic Magnetic Topological Insulator^*

TLDR

Intrinsic magnetic topological insulators are stoichiometric magnetic compounds that combine inherent magnetic order with topological electronic states, offering a pathway to novel quantum effects that have yet to be realized experimentally. We fabricated high‑quality MnBi₂Te₄ thin films by alternately depositing Bi₂Te₃ quintuple layers and MnTe bilayers via molecular beam epitaxy. The resulting films display Dirac surface states, antiferromagnetic bulk order with ferromagnetic surfaces, and support quantum anomalous Hall and axion insulator phases, as confirmed by ARPES, magnetic and transport measurements, and first‑principles calculations.

Abstract

Intrinsic magnetic topological insulator (TI) is a stoichiometric magnetic compound possessing both inherent magnetic order and topological electronic states. Such a material can provide a shortcut to various novel topological quantum effects but remains elusive experimentally so far. Here, we report the experimental realization of high-quality thin films of an intrinsic magnetic TI---MnBi$_2$Te$_4$---by alternate growth of a Bi$_2$Te$_3$ quintuple-layer and a MnTe bilayer with molecular beam epitaxy. The material shows the archetypical Dirac surface states in angle-resolved photoemission spectroscopy and is demonstrated to be an antiferromagnetic topological insulator with ferromagnetic surfaces by magnetic and transport measurements as well as first-principles calculations. The unique magnetic and topological electronic structures and their interplays enable the material to embody rich quantum phases such as quantum anomalous Hall insulators and axion insulators in a well-controlled way.