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Electrically Tunable Localized versus Delocalized Intralayer Moir\'e Excitons and Trions in a Twisted MoS$_2$ Bilayer

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posted on 2023-01-12, 15:15 authored by Medha Dandu, Garima Gupta, Pushkar Dasika, Kenji Watanabe, Takashi Taniguchi, Kausik Majumdar
Moir\'e superlattice-induced sub-bands in twisted van der Waals homo- and hetero-structures govern their optical and electrical properties, rendering additional degrees of freedom such as twist angle. Here, we demonstrate the moir\'e superlattice effects on the intralayer excitons and trions in a twisted bilayer of MoS$_2$ of H-type stacking at marginal twist angles. We identify the emission from localized and multiple delocalized sub-bands of intralayer moir\'e excitons and show their electrical modulation by the corresponding trion formation. The electrical control of the oscillator strength of the moir\'e excitons also results in a strong tunability of resonant Raman scattering. We find that the gate-induced doping significantly modulates the electronic moir\'e potential, however leaves the excitonic moir\'e confinement unaltered. This effect, coupled with variable moir\'e trap filling by tuning the optical excitation density, allows us to delineate the different phases of localized and delocalized moir\'e trions. We demonstrate that the moir\'e excitons exhibit strong valley coherence that changes in a striking non-monotonic W-shape with gating due to motional narrowing. These observations from the simultaneous electrostatic control of quasiparticle-dependent moir\'e potential will lead to exciting effects of tunable many-body phenomena in moir\'e superlattices.



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