Topological magnon modes of a chain of magnetic spheres in a waveguide

Abstract

We study topological features of a bipartite chain of magnetic spheres embedded in a rectangular metallic waveguide. The coherently coupled chain via the waveguide mode can host two topologically distinct phases identified by the Zak phase. A finite chain supports a pair of doubly degenerate topological edge states within the gap when the intercoupling dominates over the intracoupling, demonstrating that despite the strong coupling to the waveguide mode, the bulk-edge correspondence still holds. The nontrivial (trivial) topological phase is determined by the intracell and intercell coupling of magnetic spheres which depend on the separation, the external magnetic inductions, and the waveguide dimensions. Magnetically tunable topological magnon modes may enable unprecedented topological photonic devices.