Nature of Long-Lived Moiré Interlayer Excitons in Electrically Tunable MoS<sub>2</sub>/MoSe<sub>2</sub> Heterobilayers
Evgeny M. Alexeev, Carola M. Purser, Carmem M. Gilardoni, James Kerfoot, Hao Chen, Alisson R. Cadore, Bárbara L. T. Rosa, Matthew S. G. Feuer, Evans Javary, Patrick Hays, Kenji Watanabe, Takashi Taniguchi, Sefaattin Tongay, Dhiren M. Kara, Mete Atatüre, Andrea C. Ferrari
Abstract
High Resolution Image Download MS PowerPoint Slide Interlayer excitons in transition-metal dichalcogenide heterobilayers combine high binding energy and valley-contrasting physics with a long optical lifetime and strong dipolar character. Their permanent electric dipole enables electric-field control of the emission energy, lifetime, and location. Device material and geometry impact the nature of the interlayer excitons via their real- and momentum-space configurations. Here, we show that interlayer excitons in MoS 2 /MoSe 2 heterobilayers are formed by charge carriers residing at the Brillouin zone edges, with negligible interlayer hybridization. We find that the moiré superlattice leads to the reversal of the valley-dependent optical selection rules, yielding a positively valued g-factor and cross-polarized photoluminescence. Time-resolved photoluminescence measurements reveal that the interlayer exciton population retains the optically induced valley polarization throughout its microsecond-long lifetime. The combination of a long optical lifetime and valley polarization retention makes MoS 2 /MoSe 2 heterobilayers a promising platform for studying fundamental bosonic interactions and developing excitonic circuits for optical information processing.