Selective Amplification of the Primary Exciton in a MoS2 Monolayer

Optoelectronics applications for transition-metal dichalcogenides are still limited by weak light absorption and their complex exciton modes are easily perturbed by varying excitation conditions because they are inherent in atomically thin layers. Here, we propose a method of selectively amplifying the primary exciton (A(0)) among the exciton complexes in monolayer MoS2 via cyclic reexcitation of cavity-free exciton-coupled plasmon propagation. This was implemented by partially overlapping a Ag nanowire on a MoS2 monolayer separated by a thin SiO2 spacer. Exciton-coupled plasmons in the nanowire enhance the A(0) radiation in MoS2. The cumulative amplification of emission enhancement by cyclic plasmon traveling reaches approximately twentyfold selectively for the A(0), while excluding other B exciton and multiexciton by significantly reduced band filling, without oscillatory spectra implying plasmonic cavity effects.