Luminescent emission of excited Rydberg excitons from monolayer WSe2

TL;DR

This paper reports the first experimental observation of Rydberg excitons in monolayer WSe2, revealing their size, binding energy, and magnetic properties through advanced spectroscopic techniques.

Contribution

It provides direct experimental evidence of Rydberg excitons in monolayer WSe2 and characterizes their magnetic and energetic properties, advancing understanding of 2D excitonic systems.

Findings

Observation of excitonic emission up to 4s state

Estimated exciton binding energy of about 170 meV

Monotonic increase of g-factor with excited states

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 Tesla. We confirm the progressively larger exciton size for higher energy excited states through diamagnetic shift measurements. This also enables us to estimate the 1s exciton binding energy to be about 170 meV, which is significantly smaller than most previous reports. The Zeeman shift of the 1s to 3s states, from both luminescence and absorption measurements, exhibits a monotonic increase of 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.