Plasmonic diastereomers: adding up chiral centers.

We construct chiral plasmonic molecules by assembling two individual chiral centers. Interestingly, depending on the exact arrangement of the centers, all combinations result in a chiral compound with a strong chiral optical response. Furthermore, we demonstrate that the overall circular dichrosim (CD) is determined by the response of the individual chiral centers. We find that the CD spectra of the composite molecules are then simply given as the sum of the CD spectra of the constituting building blocks. Interestingly, as soon as strong near-field coupling takes place between chiral centers, we find strong deviation from the simple additive chiral behavior. Most importantly, we demonstrate that the optical response of complex chiral plasmonic systems can be decomposed and understood in terms of fundamental building blocks, offering simple and straightforward design rules for future applications such as chiral optical elements and enantiomer sensors.