Twist-Angle Dependent Interlayer Exciton Emission in MoSe2-WSe2 Heterostructures*

Two-dimension materials can be stacked together to realize van der Waals heterostructures that host novel optical and electronic properties. By stacking two different transition metal dichalcogenide semiconductors together, interlayer excitons (IXs) can be realized, which are composed of electrons and holes located in different layers. Recent studies in MoSe₂-WSe₂ heterostructures have shown bright IX photoluminescence (PL) when the twist-angle between layers is close to 0 (R-type stacking) or 60 (H-type stacking). Previously it has been shown that R and H type heterostructures exhibit twist-angle dependent polarization properties due to the valley dependent optical selection rules. In this presentation, I will discuss several significant differences between the optical response of R-type and H-type hBN encapsulated MoSe₂-WSe₂ heterostructures.I will show that the two types of heterostructures (R and H) exhibit qualitatively different dependencies of PL intensity as a function of temperature and excitation power. Time resolved PL measurements further distinguish R and H type IXs, where the latter exhibits a density dependent lifetime which we attribute to intervalley scattering.