Angle- and polarization-resolved luminescence from suspended and hexagonal boron nitride encapsulated MoSe2 monolayers

The polarized photoluminescence from atomically thin transition metal dichalcogenides is a frequently applied tool to scrutinize optical selection rules and valley physics, yet it is known to sensibly depend on a variety of internal and exter-nal material and sample properties. In this work, we apply combined angle-and polarization-resolved spectroscopy to explore the interplay of excitonic physics and phenomena arising from the commonly utilized encapsulation procedure on the optical properties of atomically thin MoSe2. We probe monolayers prepared in both suspended and encapsulated manners. We show that the hBN encapsulation significantly enhances the linear polarization of exciton photolumines-cence emission at large emission angles. This degree of linear polarization of excitons can increase up to similar to 17% in the hBN encapsulated samples. As we confirm by finite-difference time-domain simulations, it can be directly connected to the optical anisotropy of the hBN layers. In comparison, the linear polarization at finite exciton momenta is signifi-cantly reduced in a suspended MoSe2 monolayer, and becomes notable only in cryogenic conditions. This phenomenon strongly suggests that the effect is rooted in the k-dependent anisotropic exchange coupling inherent in 2D excitons. Our results have strong implications on further studies on valley contrasting selection rules and valley coherence phenomena using standard suspended and encapsulated samples. Published by Optica Publishing Group under the terms of the Creative Commons Attribution 4.0 License.