Coupled electric dipole model for a Su–Schrieffer–Heeger chain of optically resonant coreshell nanoparticles

Coreshell nanoparticles can combine optical features of different materials in a single nanostructure, which makes them interesting for many applications from biomedicine to energy harvesting. On the other hand, periodic arrays of plasmonic nanoparticles can exhibit topological phenomena such as topological edge states. Here, we study periodic chains of Si@Ag coreshell nanoparticles. For this task, we combine the hybridization of surface plasmonic modes in complex nanostructures with the coupled electric dipole formalism employed for modeling the scattering of light by periodic arrays of small plasmonic nanoparticles. We propose treating a coreshell nanoparticle as several coupled electric dipoles instead of just one and show how this is a more appropriate framework to study arrays of coreshell nanoparticles. This method allows us to build a one-to-one connection between the resonant modes of the nanoparticles and the dispersion bands of the system. Within this formalism, we show that a quasi-static Su–Schrieffer–Heeger chain of coreshell Si@Ag nanoparticles hosts multiple topological edge states at different bandgaps with tunable frequencies.