Study of momentum-resolved exciton dynamics in Monolayer Tungsten Disulfide*

Monolayer transition metal dichalcogenides (TMDs) exhibit unique characteristics among semiconductors. Desirable features such as direct bandgaps at K-points and highly efficient light-matter coupling have led to many potential applications in electronics, optoelectronics, and quantum devices. Recently, time and angle-resolved photoemission spectroscopy (TR-ARPES)  techniques have succeeded in accessing the momentum-resolved dynamics of excitons in monolayer TMDC materials, such as WSe₂ [1], and WS₂ [2]. Here, we further probe the exciton dynamics in CVD grown monolayer WS₂ samples using TR-ARPES by applying a variety of pump photoexcitation conditions, such as intensity and pump wavelength. Our results provide valuable insight into the ultrafast dynamics between free carriers, bright excitons and dark excitons.

[1]       J. Madéo et al., “Directly visualizing the momentum-forbidden dark excitons and their dynamics in atomically thin semiconductors,” Science (80), vol. 1204, pp. 1199–1204, 2020.

[2]       R. Wallauer et al., “Momentum-Resolved Observation of Exciton Formation Dynamics in Monolayer WS 2,” Nano Lett., vol. 21, pp. 5867–5873, 2021.