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2D semiconductors, such as monolayer transition metal dichalcogenides (TMDCs), have drawn significant attention owing to their unique electrical and optical properties. Despite this attention, much remains to be known about the excited states of these materials in momentum space. Recently, time- and angle- resolved photoemission spectroscopy (TR-ARPES) has been successfully applied to provide a momentum space prospective of the excitonic states in WSe₂ monolayer and multilayered heterostructures ^1-3. Here we simultaneously access both the excitons and free carriers in monolayer WS₂ across the entire first Brillouin zone. Thereby, we provide a direct measurement of the excited state properties, which critically determine the optoelectronic properties of 2D semiconductors.

[1] Madéo, J. et al. Directly visualizing the momentum-forbidden dark excitons and their dynamics in atomically thin semiconductors. Science 370, 1199-1204, 2020.

[2] Man, M. K. L. et al. Experimental measurement of the intrinsic excitonic wave function. Sci. Adv. 7, eabg0192, 2021.

[3] Karni, O. et al. Structure of the moiré exciton captured by imaging its electron and hole. Nature 603, 247-252, 2022.