Maity, I and Naik, MH and Maiti, PK and Krishnamurthy, HR and Jain, M (2020) Phonons in twisted transition-metal dichalcogenide bilayers: Ultrasoft phasons and a transition from a superlubric to a pinned phase. In: Physical Review Research, 2 (1).
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Abstract
The tunability of the interlayer coupling by twisting one layer with respect to another layer of two-dimensional materials provides a unique way to manipulate the phonons and related properties. We refer to this engineering of phononic properties as twistnonics. We study the effects of twisting on low-frequency shear modes (SMs) and layer breathing modes in a transition-metal dichalcogenide (TMD) bilayer using atomistic classical simulations. We show that these low-frequency modes are extremely sensitive to twisting and can be used to infer the twist angle. We find ultrasoft phason modes (frequency â1cm-1, comparable to acoustic modes) for any nonzero twist, corresponding to an effective translation of the moiré lattice by relative displacement of the constituent layers in a nontrivial way. Unlike the acoustic modes, the velocity of the phason modes are quite sensitive to the twist angle. Also, high-frequency SMs appear for small twist angles, identical to those in stable bilayer TMD (θ=0â or 60â), due to the overwhelming growth of stable stacking regions in relaxed twisted structures. Our study reveals the possibility of an intriguing θ-dependent superlubric to pinning behavior and of the existence of ultrasoft modes in all two-dimensional materials. © 2020 authors. Published by the American Physical Society.
| Item Type: | Journal Article |
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| Publication: | Physical Review Research |
| Publisher: | American Physical Society |
| Additional Information: | The copyright for this article belongs to the Authors. |
| Keywords: | Phonons; Shear flow, Classical simulation; Effective translation; High frequency HF; Interlayer coupling; Low-frequency modes; Relative displacement; Transition metal dichalcogenides; Two-dimensional materials, Transition metals |
| Department/Centre: | Division of Physical & Mathematical Sciences > Physics |
| Date Deposited: | 24 Jan 2023 07:11 |
| Last Modified: | 24 Jan 2023 07:11 |
| URI: | https://eprints.iisc.ac.in/id/eprint/79392 |
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