Topological magnon insulators: Chern numbers and surface magnons

摘要

Within the framework of a quantum-mechanical Heisenberg model, we address the topology of the magnon band structures of ferromagnetic pyrochlores, in particular Lu_2V_2O_7. The bridge from Chern numbers of bulk magnons to essential properties of topological surface magnons is constructed by the bulk-boundary correspondence. The topological properties of the system which originate from the Dzyaloshinskii-Moriya interaction and show up as nonzero Berry curvatures suggest a method to clearly distinguish topological surface magnons from other, trivial magnons. The method is illustrated with regard to experiments.