Plasmon–exciton coupling between plasmons and chiral molecules in core–shell structure under circularly polarized light excitation

In plasmonic induced chirality, the circular dichroism of achiral nanoparticles (NPs) caused by Coulombic interactions between metal nanoparticles (NPs) and chiral molecules has been studied. Under resonance conditions, dye molecules and metal NPs produce large Rabi splitting due to strong coupling. If the resonance of chiral molecules is at the resonance of the plasmon, it is unclear what will happen to the strong interactions between the chiral plasmon and chiral molecules. In this paper, we investigate a coupled spherical core–shell model and analyze its spectra under excitation by circularly polarized light (CPL). Based on the Coulombic interactions between NPs and chiral molecules, we demonstrate how various factors affect this coupling. We have determined that three mechanisms are responsible for the interactions between plasmons and chiral molecules: strong coupling (Rabi splitting up to 243 meV), enhanced absorption, and induced transparency. The interactions between CPL and chiral molecules with same chiralities are stronger than those of the opposite chirality. The linewidth values of the splitted peaks are closer than those of the opposite chirality, which shows that for Rabi splitting with chiral molecules, there are more complicated mechanisms responsible for the interactions. This result will be helpful for further investigation of interactions between plasmons and chiral molecules.