Routing the Exciton Emissions of WS 2 Monolayer with the High-Order Plasmon Modes of Ag Nanorods.

Locally routing the exciton emissions in two-dimensional (2D) transition-metal dichalcogenides along different directions at the nanophotonic interface is of great interest in exploiting the promising 2D excitonic systems for functional nano-optical components. However, such control has remained elusive. Herein we report on a facile plasmonic approach for electrically controlled spatial modulation of the exciton emissions in a WS 2 monolayer. The emission routing is enabled by the resonance coupling between the WS 2 excitons and the multipole plasmon modes in individual silver nanorods placed on a WS 2 monolayer. Different from prior demonstrations, the routing effect can be modulated by the doping level of the WS 2 monolayer, enabling electrical control. Our work takes advantage of the high-quality plasmon modes supported by simple rod-shaped metal nanocrystals for the angularly resolved manipulation of 2D exciton emissions. Active control is achieved, which offers great opportunities for the development of nanoscale light sources and nanophotonic devices.