Twist Angle-Dependent Phonon Hybridization in WSe2/WSe2 Homobilayer

Bera, KP and Solanki, D and Mandal, S and Biswas, R and Taniguchi, T and Watanabe, K and Raghunathan, V and Jain, M and Sood, AK and Das, A (2024) Twist Angle-Dependent Phonon Hybridization in WSe2/WSe2 Homobilayer. In: ACS Nano, 18 . 24379 -24390.

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Abstract

The emerging moiré superstructure of twisted transition metal dichalcogenides (TMDs) leads to various correlated electronic and optical properties compared to those of twisted bilayer graphene. In such a versatile architecture, phonons can also be renormalized and evolve due to atomic reconstruction, which, in turn, depends on the twist angle. However, observing this reconstruction and its relationship to phonon behavior with conventional, cost-effective imaging methods remains challenging. Here, we used noninvasive Raman spectroscopy on twisted WSe2/WSe2 (t-WSe2) homobilayers to examine the evolution of phonon modes due to interlayer coupling and atomic reconstruction. Unlike in the natural bilayer (NB), �0° as well as �60° t-WSe2 samples, the nearly degenerate A1g/E2g mode in the twisted samples (1-7°) split into a doublet in addition to the nondegenerate B2g mode, and the maximum splitting is observed around 2-3°. Our detailed theoretical calculations qualitatively capture the splitting and its dependence as a function of the twist angle and highlight the role of the moiré potential in phonon hybridization. Additionally, we found that around the 2° twist angle, the anharmonic phonon-phonon interaction is higher than the natural bilayer and decreases for larger twist angles. Interestingly, we observed anomalous Raman frequency softening and line-width increase with the decreasing temperature below 50 K, pointing to the combined effect of enhanced electron-phonon coupling and cubic anharmonic interactions in moiré superlattice. © 2024 American Chemical Society

Item Type:	Journal Article
Publication:	ACS Nano
Publisher:	American Chemical Society
Additional Information:	The copyright for this article belongs to publishers.
Keywords:	Niobium compounds; Phonons; Photoreactivity; Thermography (imaging); Tungsten compounds, Anharmonicities; Bi-layer; Hybridisation; Moiré homobilayer; Phonon anharmonicity; Phonon hybridization; Splittings; Tungsten diselenide; Twist angles; Twistronic, Selenium compounds
Department/Centre:	Division of Electrical Sciences > Electrical Communication Engineering Others Division of Physical & Mathematical Sciences > Physics
Date Deposited:	15 Sep 2024 10:47
Last Modified:	15 Sep 2024 10:47
URI:	http://eprints.iisc.ac.in/id/eprint/86096

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