Abstract
We study the interface physics of bipartite magnetic materials deposited on a topological insulator. Our study comprises antiferromagnets as well as ferrimagnets and ferromagnets with multiple magnetic moments per unit cell. If an energy gap is induced in the Dirac states on the topological surface, a topological magnetoelectric effect has been predicted. Here, we show that this effect can act in opposite directions on the two components of the magnet in a certain parameter region. Consequently, an electric field will mainly generate a staggered field rather than a net magnetization in the plane. This result is relevant for current attempts to detect the magnetoelectric effect experimentally, as well as for possible applications. We take a field-theoretic approach that includes the quantum fluctuations of both the Dirac fermions on the topological surface and the fermions in the surface layer of the magnet in an analytically solvable model. The effective Lagrangian and the Landau-Lifshitz equation describing the interfacial magnetization dynamics are derived.
- Received 21 February 2017
DOI:https://doi.org/10.1103/PhysRevB.95.155430
©2017 American Physical Society