Angle- and polarization-resolved luminescence from suspended and hexagonal Boron Nitride encapsulated MoSe₂ monolayers

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 transition metal dichalcogenides. In our study, we probe MoSe₂ monolayers which are prepared in both a suspended, as well as an encapsulated manner. We show that the hBN encapsulation significantly enhances the linear polarization of exciton PL emission at large emission angles. This degree of linear polarization of excitons can increase up 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 significantly reduced in suspended MoSe₂ monolayer, and only becomes notable at cryogenic conditions. This phenomenon strongly suggest that the effect is rooted in the k-dependent anisotropic exchange coupling inherent in 2D excitons.