Dynamics of Moiré Exciton in a Twisted MoSe2/WSe2 Heterobilayer

Abstract

AbstractMoiré potential by stacking two monolayers with slightly different lattice mismatches acts as periodic quantum confinement for optically generated excitons and provides spatially ordered 0D quantum systems. Fundamental studies on intrinsic optical phenomena in the moiré exciton are conducted; however, the excitonic states and, particularly, the dynamic properties of moiré excitons are underexplored. In this study, the unrevealed structures of moiré exciton states and their intriguing dynamics in twisted MoSe2/WSe2 heterobilayers are experimentally investigated by photoluminescence spectroscopy. Phonon‐mediated momentum dark exciton state above bright exciton state with splitting energy of ≈8 meV inside moiré potential is observed. Additionally, it is demonstrated that the dynamics of moiré excitons are determined by the radiative recombination process of bright moiré excitons at low temperatures (<20 K) and phonon‐assisted non‐radiative processes from the lowest bright to dark moiré exciton state at high temperatures (>30 K). Furthermore, additional peaks at the high‐energy side under high‐power excitation conditions are observed, which indicates emission from the triplet bright moiré exciton state with a longer decay time of 700 ns. Experimental evidence of the bright and dark exciton states within the moiré potential might provide novel platforms for quantum optics applications using moiré superlattices.