Routes to quantum anomalous Hall effect from superlattice-like magnetic topological insulators*

Recently, MnBi₂Te₄ thin films were observed to manifest the quantum anomalous Hall effect (QAHE) at a temperature of 4.5 K under magnetic field. By realizing a bulk MnBi₄Te₇ with alternating [MnBi₂Te₄] and [Bi₂Te₃] layers, we suggest that MnBi₄Te₇ is a Z₂ antiferromagnetic topological insulator with a small out-of-plane saturation field of ~ 0.2 Tesla [1]. Using model Hamiltonian analysis and first-principle calculations, we then establish a topological phase diagram and map on it with different two-dimensional configurations, which is taken from the recently-grown magnetic topological insulators MnBi₄Te₇ and MnBi₆Te₁₀. These configurations manifest various topological phases, including quantum spin Hall effect with and without time-reversal symmetry, as well as QAHE. We then provide design principles to trigger QAHE by tuning experimentally accessible knobs, such as slab thickness and magnetization [2]. Our work reveals that superlattice-like magnetic topological insulators with tunable exchange interaction serve as an ideal platform to realize the long-sought QAHE in pristine compounds.
[1] arXiv:1905.02154 (2019)
[2] Phys. Rev. Lett. 123, 096401 (2019)