Surface lattice resonances in asymmetric kagome arrangements of metallic nanoparticles

Periodic arrays strongly affect plasmon excitations in nanoparticles due to strong dipolar interactions among neighbors. The symmetry of the underlying lattice and the specific arrangement can give rise to novel effects, often mimicking electronic dispersions of low-dimensional material systems of current interest. Here we study highly asymmetric arrays of nanoparticles arranged in kagome lattices with different unit cells to probe the role of symmetries on the plasmonic surface resonance response of these structures. The symmetric system exhibits Dirac points and a dispersionless mode [1] for probing radiation fields at normal incidence, while off-normal incidence results in gap openings and split degeneracies. Asymmetric systems show a much richer behavior, as the nearest-neighbor interactions modify resonances even at normal incidence, further allowing for additional tunability. For example, nanoparticle size differences result in displaced Dirac points, and provide finite curvature to the otherwise flatband mode.  We present results for response modifications for other experimentally accessible nanoparticle systems that can dynamically simulate varying strain effects and orbital asymmetries in atomic lattices.

[1]. G. Weick, et al. PRL 110, 106801 (2013).