Exploiting oriented field projectors to open topological gaps in plasmonic nanoparticle arrays

TL;DR

This paper demonstrates how orienting elongated plasmonic nanoparticles in 1D arrays can induce topological gaps and control edge states, leveraging nanoparticle degrees of freedom beyond traditional electronic systems.

Contribution

It introduces a novel method of using nanoparticle orientation to engineer topological properties and edge states in plasmonic arrays, expanding the scope of topological nanophotonics.

Findings

Orientation of nanoparticles opens topological gaps.

Polarization controls edge state activation.

Spatial modulation enables symmetry engineering.

Abstract

In the last years there have been multiple proposals in nanophotonics to mimic topological condensed matter systems. However, nanoparticles have degrees of freedom that atoms lack of, like dimensions or shape, which can be exploited to explore topology beyond electronics. Elongated nanoparticles can act like projectors of the electric field in the direction of the major axis. Then, by orienting them in an array the coupling between them can be tuned, allowing to open a gap in an otherwise gapless system. As a proof of the potential of the use of orientation of nanoparticles for topology, we study 1D chains of prolate spheroidal silver nanoparticles. We show that in these arrays spatial modulation of the polarization allows to open gaps, engineer hidden crystalline symmetries and to switch on/off or left/right edge states depending on the polarization of the incident electric field. This opens a path towards exploiting features of nanoparticles for topology to go beyond analogues of condensed matter systems.