Search

The modified emission characteristics of a source dipole near a metal-coated topological insulator sphere are studied with the application of axion electrodynamics in the long wavelength limit. Our focus is on the effect due to the topological magneto-electric (TME) response of the sphere and its influence on the multipolar plasmonic resonance of the metallic nanoshell. It is found that the TME response mainly affects the bonding modes of the metal shell plasmons with the lower order multipole resonances experiencing appreciable red-shifts. In addition, the TME effects can lead to either greater or smaller decay rates and lower emission frequencies, depending crucially on the frequency of the emitting dipole; but otherwise rather insensitive to the orientation of the dipole moments. These findings thus provide an alternative approach to probing the TME effects via molecular fluorescence experiments, as well as new possibility of controlling the emission properties of molecules using these novel nanoparticles.

Axion electrodynamics is applied to study the response of a plasmonic nanoshell with a core made of topological insulator (TI) materials. The electric polarizability of such a system is calculated in the long wavelength limit via the introduction of two scalar potentials satisfying the various appropriate boundary conditions. Our focus is on the topological magneto-electric effect (TME) as manifested in the coupled plasmonic resonances of the nanoshell. It is found that for a TI with broken time-reversal symmetry, such TME will lead to observable red-shifts in the coupled plasmonic modes, with more significant manifestation of such shifts for the bonding modes of a metallic nanoshell. It is speculated that such universal red-shift could be a manifestation of the fundamental dual symmetry as generalized for axion electrodynamics. Keywords: Surface plasmons, Axion electrodynamics, Topological insulator, Nanoshells