Twist-Induced Chiroptical Response in Stacked Triangular Nanoprism Dimers: Leveraging the Lightning-Rod Effect

Assemblies of achiral nanoparticles spatially arranged into chiral configurations have recently emerged as notable structures for exploration in chiral plasmonics. Such architectures offer the potential for generating chiroptical responses that are several orders of magnitude larger than those of intrinsically chiral molecular systems. Despite these advancements, leveraging the strong near-field coupling by a control of the structural parameters leading to efficient chiroptical responses remains underexplored. Here, employing finite-difference time-domain (FDTD) simulations, triangular nanoprisms that are characterized by sharp vertices capable of strong electric field localization via the lightning-rod effect are used as a fundamental building block to elicit giant chiroptical response in twisted stacked dimers. Our findings reveal that the plasmon hybridization and resulting chiroptical response are highly sensitive to the structural parameters of the dimers, including the twist angle, prism thickness, and interparticle separation. Among the two hybrid mode resonances observed in the optical spectra, the nearly dark bonding mode is promising for generating strong circularly polarized light (CPL) selectivity. For dimers with optimized structural parameters, we observe exceptionally high dissymmetry factors reaching up to −1.5 at the bonding mode. A comparative study with square nanoprism dimers underscores the superiority of triangular nanoprisms over prisms with less sharp vertices. Additionally, the g -factor is largely unaffected by the material composition of the prism. Our simulations establish that twisted triangular nanoprism dimers are a simple yet elegant plasmonic architecture that holds immense potential for advanced chiral plasmonic applications.