# Inter-layer charge transport controlled by exciton-trion coherent coupling

## TL;DR

This paper demonstrates that coherent exciton-trion coupling enables stable, high-speed inter-layer charge transport in a graphene-WS2 heterojunction, advancing room-temperature trion-based electronic devices.

## Contribution

It reveals the ultrafast formation and transport of trions via coherent coupling in a heterojunction, a novel mechanism for excitonic device control.

## Key findings

- Trions are stable up to 463 K at the junction.
- Photocurrent arises from ultrafast exciton-trion coherent coupling.
- Demonstrates potential for room-temperature trionics.

## Abstract

The possibility of electrical manipulation and detection of charged exciton (trion) before its radiative recombination makes it promising for excitonic devices. Using a few-layer graphene/monolayer WS$_{2}$/monolayer graphene vertical heterojunction, we report inter-layer charge transport from top few-layer graphene to bottom monolayer graphene, mediated by coherently formed trion state. This is achieved by using a resonant excitation and varying the sample temperature, the resulting change in the WS$_{2}$ 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 ultra-fast formation of trion through exciton-trion coherent coupling, followed by its fast inter-layer transport. The demonstration of coherent formation, high stabilization, vertical transportation and electrical detection of trions marks a step towards room temperature trionics.