Orbital, spin and valley contributions to Zeeman splitting of excitonic resonances in MoSe2, WSe2 and WS2 Monolayers

• Published in: 2d materials 2019-01, Vol.6 (1)
• Main Authors: Koperski, Maciej, Molas, Maciej R, Arora, Ashish, Nogajewski, Karol, Bartos, Miroslav, Wyzula, Jan, Vaclavkova, Diana, Kossacki, Piotr, Potemski, Marek
• Format: Article
• Language: English
• Subjects: excitons; magneto-optical studies; transition metal dichalcogenide monolayers
• ISSN: 2053-1583
• DOI: 10.1088/2053-1583/aae14b

We present a comprehensive optical study of the excitonic Zeeman effects in transition metal dichalcogenide monolayers, which are discussed comparatively for selected materials: MoSe2, WSe2 and WS2. We introduce a simple semi-phenomenological description of the magnetic field evolution of individual electronic states in fundamental sub-bands by considering three additive components: valley, spin and orbital terms. We corroborate the validity of the proposed description by inspecting the Zeeman-like splitting of neutral and charged excitonic resonances in absorption-type spectra. The values of all three terms are estimated based on the experimental data, demonstrating the significance of the valley term for a consistent description of magnetic field evolution of optical resonances, particularly those corresponding to charged states. The established model is further exploited for discussion of magneto-luminescence data. We propose an interpretation of the observed large g-factor values of low energy emission lines, due to so-called bound/localized excitons in tungsten based compounds, based on the brightening mechanisms of dark excitonic states.