Modulation of Circular Dichroism in Plasmonic Nanocomplex: The Interplay Between Symmetry Breaking and Interaction

Making use of the tunability of the nanocomplex, we investigate the chiroptical properties of plasmonic hybrid nanostructures composed of a nanosphere (NS) and a twisted nanorod (NR) dimer, paying attention to the important roles of symmetry and interaction. With the help of the analytical method based on the coupled dipole model (CDM) and finite-difference time domain (FDTD) simulation, our studies show that the interparticle interaction results in induced circular dichroism (CD) at the plasmonic resonance of achiral nanosphere. Moreover, the interplay between symmetry breaking and interaction leads to an optimal configuration for the maximum chiral response. In addition, we may achieve symmetry selective interaction channels (NR-NR versus NR-NS) and related lineshapes of circular dichroism (bisignate lineshape versus unimodal lineshape). The chiroptical response can be effectively modulated by tuning the twist angle and relative positions of NRs and NS, which may have important applications in optical devices based on chiral optics.