Quantum versus optical interaction contribution to giant spectral splitting in a strongly coupled plasmon–molecules system
Bo Wang1,†, Xian-Zhe Zeng2,†, and Zhi-Yuan Li1,*
- 1School of Physics and Optoelectronic Technology, South China University of Technology, Guangzhou 510640, China
- 2School of Physics, Peking University, Beijing 100871, China
Vacuum Rabi splitting, which stems from a single photon interaction with a quantum emitter (a single atom, molecule, or quantum dot), is a fundamental quantum phenomenon. Many reports have claimed that using J aggregate coupling to highly localized plasmon can produce giant Rabi splitting (in scattering spectra) that is proportional to , where is the number of excitons in J aggregates, and this splitting originates purely from quantum interaction between excitons and plasmons. In this work, we show that the scattering spectra are very sensitive to the surrounding matter, and the giant spectral splitting stems both from the quantum interaction of a single molecule with plasmons (Rabi splitting) and from the classical optical interaction of multiple molecules with plasmons. We develop a Lorentzian model to describe molecules and plasmon and find that the collective optical interaction is dominant in generating the giant splitting (in scattering spectra), which is also proportional to , upon the quantum interaction of single-molecule Rabi splitting. Simply speaking, the observed giant spectral splitting is not a pure quantum Rabi splitting effect, but rather a mixture contribution from the large spectral modulation by the collective optical interaction of all molecules with plasmons and the modest quantum Rabi splitting of a single molecule strongly coupled with plasmons.