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

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 momentsm^(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 ofm^(θ,ϕ). In particular, the restoration of in-plane mirror symmetry for specific values ofφdrives a topological phase transition upon varying the in-plane orientation of the momentsm^(θ=90∘,ϕ). In contrast, for fixedφ, the transitions driven by varyingθoriginate from the competition between R-SOC and I-SOC. Density functional theory calculations for the ferromagnetic kagome monolayer Co₃Pb₃S₂, a representative compound belonging to the family Co₃X₃Y₂(X = Sn, Pb; Y = S, Se), corroborate our predictions based on the proposed minimal tight-binding model.