“…Plexciton, coherently coupled plasmon and exciton [1,2], brings strong light-matter interaction to room temperature [3,4] and expands the applications of cavity quantum electrodynamics (cQED) to plasmonic systems for fundamental physics [5][6][7][8], biological sensing [9][10][11] and chemical reactions [12][13][14][15]. In doing so, various plasmonic nanostructures, such as nanowaveguides [16][17][18], nanoantennas [19][20][21][22], nanogaps [11,[23][24][25], and nanoarrays [6,[26][27][28], have been designed to realize Rabi splitting [29][30][31], to suppress quenching [32][33][34], and to enhance local density of optical states [35][36][37][38]. Excitingly, these plasmonic nanostructures generally possess ultrasmall mode volumes, thus enabling strong and ultrastrong coupling with quantum emitters (QEs) [19,23,24,39,40].…”