  Plasmonic lattice nanostructures are of technological interest because of
their capacity to manipulate light below the diffraction limit. Here, we
present a detailed study of dark and bright modes in the visible and
near-infrared energy regime of an inverted plasmonic honeycomb lattice by a
combination of Au+ focused ion beam lithography with nanometric resolution,
optical and electron spectroscopy, and finite-difference time-domain
simulations. The lattice consists of slits carved in a gold thin film,
exhibiting hotspots and a set of bright and dark modes. We proposed that some
of the dark modes detected by electron energy-loss spectroscopy are caused by
antiferroelectric arrangements of the slit polarizations with two times the
size of the hexagonal unit cell. The plasmonic resonances take place within the
0.5_2 eV energy range, indicating that they could be suitable for a synergistic
coupling with excitons in two-dimensional transition metal dichalcogenides
materials or for designing nanoscale sensing platforms based on near-field
enhancement over a metallic surface.
