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.