Nature of Long-Lived\nMoire Interlayer Excitons\nin Electrically Tunable MoS<sub>2</sub>/MoSe<sub>2</sub> Heterobilayers

Interlayer excitons in transition-metal dichalcogenide\nheterobilayers\ncombine high binding energy and valley-contrasting physics with a\nlong optical lifetime and strong dipolar character. Their permanent\nelectric dipole enables electric-field control of the emission energy,\nlifetime, and location. Device material and geometry impact the nature\nof the interlayer excitons via their real- and momentum-space configurations.\nHere, we show that interlayer excitons in MoS<sub>2</sub>/MoSe<sub>2</sub> heterobilayers are formed by charge carriers residing at\nthe Brillouin zone edges, with negligible interlayer hybridization.\nWe find that the moiré superlattice leads to the reversal of\nthe valley-dependent optical selection rules, yielding a positively\nvalued g-factor and cross-polarized photoluminescence. Time-resolved\nphotoluminescence measurements reveal that the interlayer exciton\npopulation retains the optically induced valley polarization throughout\nits microsecond-long lifetime. The combination of a long optical lifetime\nand valley polarization retention makes MoS<sub>2</sub>/MoSe<sub>2</sub> heterobilayers a promising platform for studying fundamental bosonic\ninteractions and developing excitonic circuits for optical information\nprocessing.