Ferromagnetic quantum spin hall effect in 2D rare-earth nitride van der Waals heterostructures

The manipulation of topological electronic states is a key scientific challenge in the development of next-generation quantum devices. In this work, we propose a universal topological engineering strategy based on magnetic symmetry control, realized via van der Waals heterostructures of rare-earth nitrides and an inert GaS spacer, denoted as XN₂/GaS/XN₂ (X = Gd, Tb, Dy, Ho, Tm, Er). This platform enables programmable topological phase transitions between ferromagnetic quantum spin Hall insulators (QSHIs) and antiferromagnetic quantum anomalous Hall insulators (QAHIs). By continuously tuning the in-plane magnetization direction, the Berry curvature distribution is effectively modulated, inducing periodic transitions between topologically trivial and nontrivial states. Taking ErN₂/GaS/ErN₂ as a representative system, we track the evolution of the Chern number and ℤ₂ invariant with magnetization orientation, demonstrating a reversible switching between QSHI and QAHI phases. The same mechanism is found to operate across the full series of XN₂/GaS/XN₂ heterostructures, establishing its generality. These results offer both a robust theoretical framework and a practical material platform for the magnetization-controlled realization of quantum spin and anomalous Hall phases in two-dimensional magnetic van der Waals systems, paving the way for reconfigurable topological devices.