Interlayer excitons in bilayer MoS 2 with strong oscillator strength up to room temperature

I.C. Gerber (1) , Emmanuel Courtade , Shivangi Shree , Cédric Robert , Takashi Taniguchi , Kenji Watanabe , Andrea Balocchi , Pierre Renucci , Delphine Lagarde , Xavier Marie , Bernhard Urbaszek

1 LPCNO - Laboratoire de physique et chimie des nano-objets

Coulomb bound electron-hole pairs, excitons, govern the optical properties of semiconducting transition-metal dichalcogenides like MoS 2 and WSe 2. We study optical transitions at the K point for 2H homobilayer MoS 2 in density functional theory including excitonic effects and compare them with reflectivity measurements in high-quality samples encapsulated in hexagonal BN. In both calculated and measured spectra we find a strong interlayer exciton transition in energy between A and B intralayer excitons, observable for T = 4-300 K, whereas no such transition is observed for the monolayer in the same structure in this energy range. The interlayer excitons consist of an electron localized in one layer and a hole state delocalized over the bilayer, which results in the unusual combination of high oscillator strength and a static dipole moment. We also find signatures of interlayer excitons involving the second-highest valence band (B) and compare absorption calculations for different bilayer stackings. For homotrilayer MoS 2 we also observe interlayer excitons and an energy splitting between different intralayer A excitons originating from the middle and outer layers, respectively.

Domaines: Autre

I.C. Gerber, Emmanuel Courtade, Shivangi Shree, Cédric Robert, Takashi Taniguchi, et al.. Interlayer excitons in bilayer MoS 2 with strong oscillator strength up to room temperature. Physical Review B: Condensed Matter and Materials Physics (1998-2015), 2019, 99 (3), ⟨10.1103/PhysRevB.99.035443⟩. ⟨hal-02366345⟩