Interlayer charge transport controlled by exciton–trion coherent coupling

The possibility of electrical manipulation and detection of a charged exciton (trion) before its radiative recombination makes it promising for excitonic devices. Using a few-layer graphene/monolayer WS2/monolayer graphene vertical heterojunction, we report interlayer charge transport from top few-layer graphene to bottom monolayer graphene, mediated by a coherently formed trion state. This is achieved by using a resonant excitation and varying the sample temperature; the resulting change in the WS2 bandgap allows us to scan the excitation around the exciton–trion spectral overlap with high spectral resolution. By correlating the vertical photocurrent and in situ photoluminescence features at the heterojunction as a function of the spectral position of the excitation, we show that (1) trions are anomalously stable at the junction even up to 463？K due to enhanced doping, and (2) the photocurrent results from the ultrafast formation of a trion through exciton–trion coherent coupling, followed by its fast interlayer transport. The demonstration of coherent formation, high stabilization, vertical transportation, and electrical detection of trions marks a step toward room-temperature trionics