Plasmon-Exciton Coupling Using DNA Templates

In the strong coupling regime, coherent energy exchange between plasmons and excitons is a phenomenon which displays distinct hybrid states. We employ the DNA origami technique to precisely position metallic nanoparticles in a defined spatial arrangement and fixed interparticle spacing. We adjust the plasmon resonance of the structure to accurately match the energy absorption of a molecular exciton (J-aggregate) by varying the nanoparticle diameter between 30~nm and 60~nm while keeping their separation distance constant ($\sim$ 5~nm). Using this pre-programmable self-assembly approach, we obtained strong plasmon-exciton coupling and studied farfield scattering at the single-structure level, displaying normal mode splitting up to 170~meV. The ability to custom-tune the plasmon frequency and to provide strong field confinement makes DNA-origami the ideal template to bottom-up assembly plasmon-exciton systems operating at room temperature and optical frequencies.