Higher-order topology in plasmonic kagome lattices

TL;DR

This paper investigates the topological phases of a plasmonic kagome lattice, revealing higher-order boundary modes like edges and corners that can confine light at subwavelength scales, with potential applications in nanophotonics.

Contribution

It introduces a coupled dipole model for plasmonic kagome lattices that captures long-range interactions and demonstrates the existence of higher-order topological boundary modes.

Findings

Identification of obstructed atomic limit phase via Wilson loops

Existence of robust edge and corner modes in the plasmonic lattice

Selective excitation of corner modes using orbital angular momentum beams

Abstract

We study the topological properties of a kagome plasmonic metasurface, modelled with a coupled dipole method which naturally includes retarded long range interactions. We demonstrate the system supports an obstructed atomic limit phase through the calculation of Wilson loops. Then we characterise the hierarchy of topological boundary modes hosted by the subwavelength array of plasmonic nanoparticles: both one-dimensional edge modes as well as zero-dimensional corner modes. We determine the properties of these modes which robustly confine light at subwavelength scales, calculate the local density of photonic states at edge and corner modes frequencies, and demonstrate the selective excitation of delocalised corner modes in a topological cavity, through non-zero orbital angular momentum beam excitation.