Spectral Splitting of Resonances in Topological Symmetry-Breaking Gyrotropic Nanostructures

We present a comprehensive study of plasmonic responses of a gyrotropic topological symmetry-breaking Möbius strip in the presence of an external magnetic field. The interplay between the magnetic field and the topology is determined by analyzing the scattering cross-section spectra and the corresponding multipole expansion. Spectral splitting of resonances is observed in such a scattering system, which is an analogue of the Zeeman splitting of atomic spectral lines. Moreover, highly tunable localized surface plasmon resonances of a wide range are realized by varying the magnetic field and the geometry. The insights into the interplay between the topology and the applied magnetic field will be of great interest for the plasmonic applications such as sensing and optical insulating.