Angle-dependent Magnetotransport in Multilayer Magnetically-doped Topological Insulators near the Zero-Hall-Plateau Quantum Anomalous Hall State

Topological insulators (TIs) are the focus of a rapidly-growing body of research due to the many interesting properties of their metallic surface states. The interaction of the surface states with other phenomenon such as magnetism or superconductivity results in novel and exotic behavior. In particular, magnetically-doped TIs have exhibited the theoretically-predicted quantum anomalous Hall (QAH) effect, in which the surface states are gapped while leaving quantized edge states even in no external magnetic field. A theoretical extension of the QAHE is the axion insulator, in which all surface states become gapped in a non-trivial fashion. While there are multiple reports claiming an axionic state, there is still much discussion of the experimental signatures expected. Here, we study a heterostructure consisting of an undoped TI layer sandwiched between magnetically-doped TI layers. Transport measurements are performed near the zero-Hall-plateau QAH insulator regime- a candidate regime for axionic behavior. Angle-resolved magnetic field dependence provides insight into the behavior of the magnetic domains and edge states, and the transition to the zero-Hall-plateau regime.