Magnon bandstructure and topology in a periodically deformed Kagome lattice with DM interaction

Abstract

We study the band structure and topology of magnons for a Heisenberg model with DM interaction on a deformed Kagome lattice. For simplicity, we focus on a periodically deformed lattice with hexagonal symmetry and an enlarged unit cell. This enlarged unit cell gives rise to a richer band structure than in the undeformed case. Analyzing band topology, there is a distinction between the topologically trivial case with anti-ferromagnetic coupling and the topologically rich case with ferromagnetic coupling. In the anti-ferromagnetic case, a spin-space symmetry, also present in the classical ground state, enforces these topologically trivial states. In the ferromagnetic case, this symmetry is spontaneously broken by the classical ground state. Consequently, the band structure also hosts rich topological features. Specifically, we observe many topological transitions and bands with Chern numbers ranging from $+2$ to $-2$, which makes the system richer than in the undeformed case. This emergent rich topological structure demonstrates that deformed magnets can host new and exciting physics.