Topology-tuned light scattering around Fano resonances by a core-shell cylinder

The topological magnetoelectric (TME) effect is a novel optical response from topological insulators. This effect shows that magnetic (electric) polarization can be induced by an applied electric (magnetic) field, and it is characterized by the fine structure constant. However, the TME effect is generally very weak and still a challenge to be observed in the experiment. In this paper, we showed that the far-field scattering of a core-shell topological cylinder can be tuned by the TME effect which was enhanced at the surface of plasmonic core around Fano resonance. The interference of broad dipolar mode and narrow quadrupole mode is changed with the topological magnetoelectric polarizability. We demonstrated the reversal of optical responses associated with the TME effect in both far-field and near field. Our results may offer an alternative way to observe the TME effect in topological insulators.