Surface-Driven Evolution of the Anomalous Hall Effect in MnBi2Te4 Thin Films: Implications for the Quantum Anomalous Hall Effect

Understanding interfacial modification of functional properties of magnetic topological insulator thin films is crucial for designing and manipulating properties and ultimately technological applications. This is especially critical for A-type antiferromagnets such as MnBi2Te4 where the magnetic compensation is dependent upon the thickness. In this talk I will discuss the large electronic and magnetic response that is induced in MnBi2Te4 by controlling the propagation of surface oxidation. This oxide is strongly confined to the top layer yet drives a dramatic reversal of the sign of the anomalous Hall effect driven by finite thickness magnetism, which indicates that the film splits into distinct magnetic layers each with a unique electronic signature. This suggests that magnetic perturbations resulting from surface oxidation may play a non-trivial role in the stabilization of the quantum anomalous Hall effect in this system and that understanding targeted modifications to the surface may open new routes for engineering novel topological and magnetic responses in this fascinating material.