Nodal lines in a honeycomb plasmonic crystal with synthetic spin

TL;DR

This paper investigates a honeycomb plasmonic crystal with synthetic spin, revealing protected nodal lines due to symmetries, verified by simulations, and tunable via Kekulé distortion, offering new design avenues for plasmonic devices.

Contribution

It demonstrates the existence and robustness of symmetry-protected nodal lines in a plasmonic honeycomb lattice using both models and simulations, and explores their tunability.

Findings

Nodal lines are protected by combined symmetries in the plasmonic lattice.

Nodal lines persist even when symmetries are weakly broken.

Kekulé distortion can lift degeneracies at the nodal lines.

Abstract

We analyze a plasmonic model on a honeycomb lattice of metallic nanodisks that hosts nodal lines protected by local symmetries. Using both continuum and tight-binding models, we show that a combination of a synthetic time-reversal symmetry, inversion symmetry, and particle-hole symmetry enforce the existence of nodal lines enclosing the $\mathrm{K}$ and $\mathrm{K}'$ points. The nodal lines are not directly gapped even when these symmetries are weakly broken. The existence of the nodal lines is verified using full-wave electromagnetic simulations. We also show that the degeneracies at nodal lines can be relieved by introducing a Kekul\'e distortion that acts to mix the nodal lines near the $\mathrm{K},\mathrm{K}'$ points. Our findings open pathways for designing novel plasmonic and photonic devices without reliance on complex symmetry engineering, presenting a convenient platform for studying nodal structures in two-dimensional systems.