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arXiv · 2301.03916

External screening and lifetime of exciton population in single-layer ReSe$_2$ probed by time- and angle-resolved photoemission spectroscopy

Klara Volckaert·Byoung Ki Choi·Hyuk Jin Kim·Deepnarayan Biswas·Denny Puntel·Simone Peli·Fulvio Parmigiani·Federico Cilento·Young Jun Chang·Søren Ulstrup
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Abstract

The semiconductor ReSe$_2$ is characterized by a strongly anisotropic optical absorption and is therefore promising as an optically active component in two-dimensional heterostructures. However, the underlying femtosecond dynamics of photoinduced excitations in such materials has not been sufficiently explored. Here, we apply an infrared optical excitation to single-layer ReSe$_2$ grown on a bilayer graphene substrate and monitor the temporal evolution of the excited state signal using time- and angle-resolved photoemission spectroscopy. We measure an optical gap of $(1.53 \pm 0.02)$ eV, consistent with resonant excitation of the lowest exciton state. The exciton distribution is tunable via the linear polarization of the pump pulse and exhibits a biexponential decay with time constants given by $τ_1 = (110 \pm 10)$ fs and $τ_2 = (650 \pm 70)$ fs, facilitated by recombination via an in-gap state that is pinned at the Fermi level. By extracting the momentum-resolved exciton distribution we estimate its real-space radial extent to be greater than 17.1 Å, implying significant exciton delocalization due to screening from the bilayer graphene substrate.

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Klara Volckaert, Byoung Ki Choi, Hyuk Jin Kim, Deepnarayan Biswas, Denny Puntel, Simone Peli, Fulvio Parmigiani, Federico Cilento, Young Jun Chang, Søren Ulstrup. 2023-01-10. External screening and lifetime of exciton population in single-layer ReSe$_2$ probed by time- and angle-resolved photoemission spectroscopy. https://doi.org/10.1103/physrevmaterials.7.l041001

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