Half-quantized Hall conductance in topological insulator/ferromagnet van der Waals heterostructures

The realization of half-quantized anomalous Hall insulators (hQAHI) is an important challenge for both theoretical and experimental research in contemporary condensed matter physics. A possible realization of hQAHI may be achieved by interfacing a two-dimensional (2D) ferromagnet on one side of a thin slab of topological insulator (TI), which breaks the otherwise conserved time-reversal symmetry, leading to a gap opening in the Dirac-like energy spectrum of the TI surface states. The resulting heterostructure can support chiral edge states where only one spin channel contributes to transport, producing a half-quantized Hall conductance (e²/2h). In this work, using first-principles methods together with tight-binding models, we investigate the magnetization-induced gap, the properties of the edge states, and Hall conductance in proposed van der Waals heterostructures. We also discuss the factors that can hinder the realization of exact half-quantization in a realistic system.