Exceptional points unveiling quantum limit of fluorescence rates in non-Hermitian plexcitonic single-photon sources

Single-photon sources based on plexcitonic systems are notable for their fast fluorescence rates, typically >100 GHz. Our investigations reveal that exceptional points (EPs) may unveil the quantum limit of fluorescence rates in plexcitonic single-photon sources. By employing a non-Hermitian Hamiltonian framework and field quantization model, we demonstrate how the fluorescence rate can be ingeniously designed in an exemplified plexcitonic system consisting of a nanocube-on-mirror cavity and a single quantum emitter. We predict the highest fluorescence rates of 11.0, 13.9, and 14.7 THz at the EPs with typical dipole moments of 25, 30, and 35 D, respectively.