Nature of Long-Lived Moiré Interlayer Excitons in Electrically Tunable MoS2/MoSe2 Heterobilayers

• Published in: Nano letters Vol. 24; no. 36; pp. 11232 - 11238
• Main Authors: Alexeev, Evgeny M., Purser, Carola M., Gilardoni, Carmem M., Kerfoot, James, Chen, Hao, Cadore, Alisson R., Rosa, Bárbara L.T., Feuer, Matthew S. G., Javary, Evans, Hays, Patrick, Watanabe, Kenji, Taniguchi, Takashi, Tongay, Seth Ariel, Kara, Dhiren M., Atatüre, Mete, Ferrari, Andrea C.
• Format: Journal Article
• Language: English
• Published: American Chemical Society 11-09-2024
• Subjects: Letter; moiré superlattice; interlayer excitons; valley polarization; photoluminescence; layered materials heterostructures; Stark shift; transition-metal dichalcogenides
• ISSN: 1530-6984; 1530-6992; 1530-6992
• DOI: 10.1021/acs.nanolett.4c02635

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 MoS2/MoSe2 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 MoS2/MoSe2 heterobilayers a promising platform for studying fundamental bosonic interactions and developing excitonic circuits for optical information processing.