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Zero Hall conductivity and its electronic origin in a Cr-doped topological insulator

We investigate the electronic origin of the zero Hall conductivity or the axion phase of a Crdoped Sb2Te3 film by analyzing the evolution of its band structure upon the magnetic field sweep. By applying a small electric field or using asymmetric doping, we differentiate the coercivities of the two surfaces, so they can form either ferromagnetic (FM) or antiferromagnetic (AFM) alignment. Through the surface-resolved Berry curvature calculations, we demonstrate that the system manifests robust zero Hall plateaus when the two surfaces remain topologically nontrivial and enter a magnetic state which has intrasurface FM and inter-surface AFM orderings. Our results provide insights for the understanding of the uncharted issues of axion insulators, complementary to the exciting experimental progresses in this realm. PACS: 75.50.Pp, 73.20.At, 73.43.Cd