Luminescent Emission of Excited Rydberg Excitons from Monolayer WSe<sub>2</sub>.

Chen, Shao-Yu; Lu, Zhengguang; Goldstein, Thomas; Tong, Jiayue; Chaves, Andrey; Kunstmann, Jens; Cavalcante, L S R; Woźniak, Tomasz et al. · Nano Lett · 2019

basic_science · Level V

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Abstract

We report the experimental observation of radiative recombination from Rydberg excitons in a two-dimensional semiconductor, monolayer WSe<sub>2</sub>, encapsulated in hexagonal boron nitride. Excitonic emission up to the 4 s excited state is directly observed in photoluminescence spectroscopy in an out-of-plane magnetic field up to 31 T. We confirm the progressively larger exciton size for higher energy excited states through diamagnetic shift measurements. This also enables us to estimate the 1 s exciton binding energy to be about 170 meV, which is significantly smaller than most previous reports. The Zeeman shift of the 1 s to 3 s states, from both luminescence and absorption measurements, exhibits a monotonic increase of the g-factor, reflecting nontrivial magnetic-dipole-moment differences between ground and excited exciton states. This systematic evolution of magnetic dipole moments is theoretically explained from the spreading of the Rydberg states in momentum space.