Anomalous Hall effects in the 2D antiferromagnet MnBi₂Te₄driven by polar layer stacking

Van der Waals (vdW) assembly of two-dimensional (2D) materials has stimulated the discovery of new physical phenomena and functional properties useful for applications. Especially interesting is the recently discovered ferroelectricity in vdW assembled materials that are non-polar in the bulk form¹. Breaking inversion symmetry accompanied by the appearance of the spontaneous electric polarization in such vdW materials opens a new direction to realize novel electronic, magnetic, and topological properties and control them by switchable polarization. Here, based on symmetry analyses and density-functional-theory calculations, we explore the emergence of the anomalous Hall effect (AHE) in antiferromagnetic MnBi₂Te₄ films assembled by polar layer stacking. Recently synthesized MnBi₂Te₄ films exhibit properties of an intrinsic magnetic topological insulator and reveal interesting quantum phenomena dependent on the number of monolayers in the film. We demonstrate that breaking PT symmetry by layer stacking in MnBi₂Te₄ films with an even number of layers produces an AHE whose sign changes by the switching of ferroelectric polarization. We find that reversable polarization at one of the interfaces in three-layer MnBi₂Te₄ films drives a metal-insulator transition, as well as switching from AHE to quantum AHE (QAHE). Finally, we predict that engineering an interlayer polarization in three-layer MnBi₂Te₄ films allows converting MnBi₂Te₄ from a trivial to nontrivial topological insulator. Overall, this work emphasizes the emergence of quantum transport phenomena in MnBi₂Te₄ films by polar layer stacking, which do not exist in this material in the bulk or bulk-like thin-film forms.

1. 1. E. Y. Tsymbal, Two-dimensional ferroelectricity by design, Science 372, 1389 (2021).