Enhanced Sensitivity with Exceptional Points in Non-Hermitian Plexcitonics

The strong coupling between plasmonic nanocavities and two-dimensional semiconductors provides a solid-state platform for compact, ultrabroadband polaritonic devices operating at room temperature. Plasmon-exciton (plexciton) hybrid systems, with their spectral tunability and intrinsic losses, are ideally suited for exploring non-Hermitian physics and miniaturized sensors. However, precise manipulation of the interaction in parameter space, an essential requirement, remains challenging at the deep-subwavelength scale, hindering experimental realization. Here, we provide a strategy to precisely tune plasmon-exciton interaction in parameter space by engineering the dielectric environment. By tuning the plasmon-exciton detuning in situ, we realize an exceptional point in a single nanocavity-WS₂ hybrid system, leading to an approximately 10-fold enhancement in sensitivity compared with conventional plasmonic sensors based on bare nanocavities. These results establish non-Hermitian plexcitonic systems as a cavity quantum electrodynamics (cQED)-based platform for ultrasensitive detection of weak external stimuli, enabling ultrafast quantum devices beyond the diffraction limit.