Realizing room-temperature strong coupling of single-exciton with plasmons by controlling quantum exceptional point

Single-exciton strong coupling with plasmons is highly desirable for exploiting room-temperature quantum devices and applications. However, the large plasmon decay makes the realization of such strong coupling extremely difficult. To overcome this challenge, here we propose an effective approach to easily achieve the single-exciton strong coupling at room temperature by controlling quantum exceptional point (QEP) of the coupling system via matching the decay between the localized plasmon mode (LPM) and exciton. The good match can be reached by suppressing the LPM’s decay with the use of a leaky Fabry-Perot cavity. Experimental results show that the LPM’s decay linewidth is greatly compressed from ~ 45 nm to ~ 15 nm, which is close to the excitonic linewidth (~ 10 nm), pushing their interaction from the Fano interference into the strong coupling. Our work opens a new way to flexibly control the QEP and more easily realize the single-exciton strong coupling in ambient conditions.