Topological phase transitions in kagome ferromagnets: the role of intrinsic Rashba spin–orbit coupling

Abstract The theoretically predicted Chern insulators have highlighted the potential of easy-axis kagome ferromagnets to host the quantum anomalous Hall effect. Similar topological phases may also arise from in-plane ferromagnetism through the breaking of certain mirror symmetries in kagome materials. In this work, we show that the interplay between magnetism and mirror symmetries makes ferromagnetic kagome systems a versatile platform for realizing nontrivial topological phases, with the orientation of magnetic moments m ^ ( θ , ϕ ) at lattice sites serving as a key tuning parameter. We construct a symmetry-adapted minimal tight-binding model for kagome ferromagnets that includes intrinsic spin–orbit coupling (I-SOC) and the intrinsic Rashba SOC (R-SOC) permitted by broken out-of-plane mirror symmetry between nearest-neighbor kagome sites, enabling us to capture the resulting topological phase diagram as a function of m ^ ( θ , ϕ ) . In particular, the restoration of in-plane mirror symmetry for specific values of φ drives a topological phase transition upon varying the in-plane orientation of the moments m ^ ( θ = 90 ∘ , ϕ ) . In contrast, for fixed φ , the transitions driven by varying θ originate from the competition between R-SOC and I-SOC. Density functional theory calculations for the ferromagnetic kagome monolayer Co 3 Pb 3 S 2 , a representative compound belonging to the family Co 3 X 3 Y 2 (X = Sn, Pb; Y = S, Se), corroborate our predictions based on the proposed minimal tight-binding model.