Direct visualization of hybridized excitons in twisted WS₂/MoSe₂ heterobilayers

Twisted heterobilayers of transition metal dichalcogenides (TMD) provide a unique and tunable platform to study properties of excitons. Particularly, in WS₂/MoSe₂ heterostructure systems, the conduction band minimum of two layers are nearly degenerate, leading to hybridization between intralayer excitons and interlayer excitons. Optical measurements including photoluminescence and reflectance spectra have shown emerging temperature- and twist-angle-dependence. To further understand the formation and evolution of hybridized excitons, we performed time-resolved angle-resolved photoemission spectroscopy (TR-ARPES) to directly visualize energetics and dynamics of exciton states in momentum space. We also characterized dynamics of samples with different twist angles at various temperature and fluence conditions. Our study has shown that moiré superlattice and band alignment play significant roles in the ultrafast exciton dynamics.