  We construct the dyadic Greens functions (DGFs) for a topological insulator
(TI) stratified sphere within the framework of axion electrodynamics. For these
DGFs, the additional expansion coefficients are included to account for the
axion coupling effect. With the application of these DGFs, we derive the
formulation of light scattering from a dipole near a TI stratified sphere. In
our numerical studies, we give three types of configurations (a metal-coated TI
sphere, a metal-TI-metal-coated TI sphere and an alternating metal-TI
stratified sphere) to investigate how the topological magneto-electric (TME)
response of the TI sphere (shells) influences on the multipolar plasmonic
resonance of the metal shells. For these types, the results show that the TME
effect causes some modifications of the decay rate spectrum for an emitting
dipole near a TI stratified sphere. For the multipolar resonances of the metal
shells, it is observed that the TME-induced red-shifts for the bonding and
lower order antibonding modes are found but those for the higher order
antibonding modes are insignificant. In addition, for a metal-coated TI sphere,
we take into account the effects of losses in the TI core of which the
dielectric function is chosen to be the form of the bulk or five quintuple
layers (5QL) slab and then the some modifications of the TME-induced decay rate
spectrum are obviously suppressed. These phenomenological characteristics
provide useful guidance to probing the TME effect via molecular fluorescence
experiments.
