Motional narrowing, ballistic transport, and trapping of room-temperature exciton polaritons in an atomically-thin semiconductor

TL;DR

This study demonstrates the creation, manipulation, and trapping of room-temperature exciton polaritons in monolayer WS2, revealing motional narrowing, ballistic transport, and suppressed dephasing, paving the way for advanced optoelectronic applications.

Contribution

It introduces a method to generate and trap TMDC polaritons at room temperature, showing extended ballistic transport and reduced dephasing in an ambient environment.

Findings

Ballistic transport of polaritons over tens of micrometers.

Significant reduction of dielectric disorder effects in strong coupling.

Suppressed dephasing of trapped polaritons compared to excitons.

Abstract

Atomically-thin transition metal dichalcogenide crystals (TMDCs) hold great promise for future semiconductor optoelectronics due to their unique electronic and optical properties. In particular, electron-hole pairs (excitons) in TMDCs are stable at room temperature and interact strongly with light. When TMDCs are embedded in an optical microcavity, the excitons can hybridise with cavity photons to form exciton polaritons (polaritons herein), which display both ultrafast velocities and strong interactions. The ability to manipulate and trap polaritons on a microchip is critical for future applications. Here, we create a potential landscape for room-temperature polaritons in monolayer WS$_2$, and demonstrate their free propagation and trapping. We show that the effect of dielectric disorder, which restricts the diffusion of WS$_2$ excitons and broadens their spectral resonance, is dramatically reduced in the strong exciton-photon coupling regime leading to motional narrowing. This enables the ballistic transport of WS$_2$ polaritons across tens of micrometers with an extended range of partial first-order coherence. Moreover, the dephasing of trapped polaritons is dramatically suppressed compared to both WS$_2$ excitons and free polaritons. Our results demonstrate the possibility of long-range transport and efficient trapping of TMDC polaritons in ambient conditions.