Excitonic Complexes in a Charge Tunable WSe2 Monolayer Device

Transition Metal Dichalcogenides (TMD) monolayers have emerged as exciting 2D materials for optoelectronics and spintronics. Due to the large exciton binding energies and strong spin-orbit coupling, these materials can host various and robust excitonic complexes. The encapsulation of TMD monolayers into hBN combined with the constant improvement of the material quality now enable to reproducibly observe and control these excitonic complexes in the optical spectra.
In this work, we study a WSe2 monolayer embedded into a charge tunable device made of graphite electrodes and hBN. This allows us to study excitonic complexes in different doping regimes (neutral, n or p). We systematically performed magneto-photoluminescence/reflectivity and time resolved photoluminescence as a function of doping to identify the nature of the excitonic transitions based on their characteristic Landé g-factor and their temporal dynamics. The fine structure of the trion (intervalley, intravalley, dark trion) will first be discussed. Phonon assisted transitions (momentum mismatch dark exciton and spin forbidden dark exciton) are also identified. Finally the origin of more complex transitions observed under high n type doping will be discussed.