Antiferromagnetic topological insulator

We have predicted by ab initio calculations and further confirmed using various experimental techniques, including high-resolution angle-resolved photoemission spectroscopy (ARPES), the realization of an antiferromagnetic (AFM) topological insulator (TI) in the layered van der Waals compound MnBi₂Te₄. This is the first observation of an intrinsic magnetic topological insulator, i.e. a stoichiometric well ordered magnetic compound. Our experiments indicate that the symmetry-breaking (0001) surface of MnBi₂Te₄ exhibits a large bandgap in the topological surface state. A number of fundamental phenomena are expected to be eventually observed, including quantized magnetoelectric coupling and axion electrodynamics. Other exotic phenomena could become accessible at temperatures significantly higher than those achieved to date on magnetic topological insulators created by the doping of non-magnetic topological insulators with 3d transition metal elements, such as the quantum anomalous Hall effect and chiral Majorana fermions.