  Topological magnon insulators support chiral edge excitations, whose lack of
electric charge makes them notoriously difficult to detect experimentally. We
show that relativistic magnetoelectric coupling universally renders chiral edge
magnons electrically active, thereby facilitating electrical probes of magnon
topology. Considering a two-dimensional out-of-plane magnetized topological
magnon insulator, we predict a fluctuation-activated electric polarization
perpendicular to the sample edges. Furthermore, the chiral topological
electromagnons give rise to a unique in-gap signal in electrical absorption
experiments. These results suggest THz spectroscopy as a promising probe for
topological magnons.
