Quantum anomalous Hall effect in a three-dimensional topological-insulator-thin-film-ferromagnetic-metal heterostructure

We theoretically show that the three-dimensional (3D) topological insulator (TI)/thin-film ferromagnetic metal (FMM) heterostructure is possible to be a quantum anomalous Hall (QAH) insulator with a wide global band gap. Studying the band structure and the weight distributions of eigenstates, we demonstrate that the attachment of a metallic thin film on the 3DTI can shift the topologically nontrivial state into the metal layers due to the hybridization of bands around the original Dirac point. By introducing the magnetic exchange interaction in the thin-film layers, we compute the anomalous Hall conductivity and magnetic anisotropy of the heterostructure to suggest the appearance of a wider gap realizing QAH effect than usual materials, such as magnetically doped thin films of 3DTI and 3DTI/ferromagnetic insulator heterostructures. Our results indicate that the 3DTI/thin-film FMM heterostructure may implement the QAH effect even at room temperature, which will pave the way to the experimental realization of the other exotic topological quantum phenomena.