Coexistence of Multiple Topological Phases and High‐Order Topology in 2D V₂CS₂, Cr₂CS₂, and Mn₂CS₂

Abstract This study investigates the topological properties of 2D , , and using first‐principles calculations. The rare coexistence of different topological fermion types is uncovered within single materials: hosts both type‐I and type‐II Dirac points, while the spin‐down channel of ferromagnetic exhibits both type‐I and type‐II Weyl points. In contrast, is identified as an antiferromagnetic insulator (gap 375 meV), and the spin‐up channel of is insulating (gap 28 meV). We demonstrate that biaxial strain can tune the fermion topology, transforming type‐II into type‐III fermions, while type‐I fermions remain robust. Spin‐orbit coupling (SOC) induces gaps at type‐I points (20‐24 meV) but leaves type‐II fermions gapless, indicating their robustness against SOC. Furthermore, the spin‐up channel of and is identified as magnetic high‐order topological insulators (HOTIs). This is confirmed by calculations of quantized fractional corner charges (e/3) protected by symmetry and the identification of topological corner states using tight‐binding models. These findings reveal a rich topological landscape in these materials, offering potential for fundamental research and applications in spintronics and quantum computing.