Quantum Anomalous Hall Effect in Three-dimensional Topological Insulator/Thin-film Ferromagnetic Metal Bilayer Structure

TL;DR

This paper theoretically demonstrates that a 3D topological insulator combined with a thin-film ferromagnetic metal can host a quantum anomalous Hall effect with a wide band gap, potentially at room temperature.

Contribution

It introduces a novel 3D TI/thin-film FMM bilayer structure as a candidate for room-temperature QAH insulators, expanding the possibilities for topological quantum devices.

Findings

The bilayer structure can host a QAH effect with a wide global band gap.

Band hybridization shifts topologically non-trivial states into metallic layers.

The structure may realize QAH at room temperature.

Abstract

We theoretically show that the three-dimensional (3D) topological insulator (TI)/thin-film ferromagnetic metal (FMM) bilayer structure 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 non-trivial 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 bilayer structure to suggest the appearance of 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 bilayer structure may implement the QAH effect even at room temperature, which will pave a way to the experimental realization of other exotic topological quantum phenomena.