Measurement of the Spin-Forbidden Dark Excitons in MoS2 and MoSe2 monolayers

Cédric Robert (1) , B. Han (1) , P. Kapuscinski (2, 3) , A. Delhomme (3) , Clément Faugeras (2) , Thierry Amand (1) , M. R. Molas (4) , M. Bartos (2, 5) , K. Watanabe (6) , T. Taniguchi (6) , B. Urbaszek , M. Potemski (1) , Xavier Marie (1)

1 LPCNO - Laboratoire de physique et chimie des nano-objets
2 LNCMI-G - Laboratoire national des champs magnétiques intenses - Grenoble
3 Wroclaw University of Science and Technology
4 UW - University of Warsaw
5 BUT - Brno University of Technology [Brno]
6 NIMS - National Institute for Materials Science

Excitons with binding energies of a few hundreds of meV control the optical properties of transition metal dichalcogenide monolayers. Knowledge of the fine structure of these excitons is therefore essential to understand the optoelectronic properties of these 2D materials. Here we measure the exciton fine structure of MoS2 and MoSe2 monolayers encapsulated in boron nitride by magneto-photoluminescence spectroscopy in magnetic fields up to 30 T. The experiments performed in transverse magnetic field reveal a brightening of the spin-forbidden dark excitons in MoS2 monolayer: we find that the dark excitons appear at 14 meV below the bright ones. Measurements performed in tilted magnetic field provide a conceivable description of the neutral exciton fine structure. The experimental results are in agreement with a model taking into account the effect of the exchange interaction on both the bright and dark exciton states as well as the interaction with the magnetic field.

Domaines: Systèmes désordonnés et réseaux de neurones [cond-mat.dis-nn]; Science des matériaux [cond-mat.mtrl-sci]

Cédric Robert, B. Han, P. Kapuscinski, A. Delhomme, Clément Faugeras, et al.. Measurement of the Spin-Forbidden Dark Excitons in MoS2 and MoSe2 monolayers. Nature Communications, 2020, 11, pp.4037. ⟨10.1038/s41467-020-17608-4⟩. ⟨hal-03026188⟩