Berry curvature and topological edge modes for coupled waves between magnons and electromagnetic waves

The Chern number characterizes existence of the chiral topological edge modes inside the gap. The chiral topological edge modes are well studied in electronic systems, and they can be realized in photonic crystals and magnonic crystals, in which the time-reversal symmetry is broken. In addition to systems with a single kind of particles, systems consisting of more than two kinds of particles or quasiparticles attract much attention recently, in the context of topological phases.
In this presentation, we consider coupled waves between magnons and electromagnetic waves in a ferromagnet. The Berry curvature is enhanced at the crossing point of dispersions, as is the case for other coupled waves such as magnons with the dipolar hybridization and magnetoelastic waves. The Chern number, i.e. the integral of the Berry curvature for the coupled waves between the magnon and the electromagnetic wave is quantized. We find that the hybridization gap in this case is topological. Therefore, there exist topological chiral edge modes inside this gap. We also present an emergence of edge modes at an interface between two topologically different regions.