Abstract
We report the experimental observation of radiative recombination from
Rydberg excitons in a two-dimensional semiconductor, monolayer WSe2,
encapsulated in hexagonal boron nitride. Excitonic emission up to the 4s
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 is exciton
binding energy to be about 170 meV, which is significantly smaller than
most previous reports. The Zeeman shift of the is to 3s 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.
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