Spin-chirality-dependent modulation of topological gap, Chern number, and valley-polarization in monolayer Kagome materials

Abstract: Kagome materials exhibit unique electronic properties, such as the quantum anomalous Hall effect. The control of Chern numbers is critical for quantum device manipulation, but existing research has mainly focused on collinear magnetization while neglecting chiral spin textures. Through first-principles calculations and tight-binding modeling of monolayer Cr3Se4, this study reveals spin chirality-dependent control of topological gaps, Chern numbers, and valley polarization in kagome materials. The results demonstrate that the azimuthal angle has no observable effect. For collinear magnetization, the topological bandgap decreases as the spin orientation approaches the in-plane direction. In the breathing Kagome lattice, the degeneracy between K and K' valleys is lifted, and increasing the polar angle induces successive closing and reopening of the valleys. For chiral spin textures, increasing polar angle enlarges the bandgap when chirality \k{appa} = 1, while reducing it when \k{appa} = -1. Moreover, spin chirality enables the quantum anomalous Hall state without spin-orbit coupling. Structural asymmetry and spin chirality effectively modulate the bandgap, Chern number, and valley polarization. These findings provide strategies for controlling topological states and advancing applications in quantum devices and valleytronic systems.