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 K and 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 K,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.
@article{arxiv.2502.00932,
title = {Nodal lines in a honeycomb plasmonic crystal with synthetic spin},
author = {Sang Hyun Park and E. J. Mele and Tony Low},
journal= {arXiv preprint arXiv:2502.00932},
year = {2025}
}