Topological effect of surface plasmon excitation in gapped isotropic topological insulator nanowires

Abstract

We present a theoretical investigation of the surface plasmon (SP) at the interface between a topologically nontrivial cylindrical core and a topologically trivial surrounding material, from the axion electrodynamics and modified constitutive relations. We find that the topological effect always leads to a red-shift of SP energy, while the energy red-shift decreases monotonically as core diameter decreases. A qualitative picture based on classical perturbation theory is given to explain these phenomena, from which we also infer that to enhance the shift, the difference between the inverse of dielectric constants of two materials must be increased. We also find that the surrounding magnetic environment suppresses the topological effect. All these features can be well described by a simple ansatz surface wave, which is in good agreement with full electromagnetic eigenmodes. In addition, bulk plasmon energy at ωp = 17.5 ± 0.2 eV for a semiconducting Bi2Se3 nanoparticle is observed from high-resolution electron energy loss spectrum measurements.