Chiral Phonons in Moiré Superlattices

We discover chiral phonons at the lowest energy bands in moiré superlattices. The moiré chiral phonons we uncover are the collective excitations of the stacking domains. Their origin is uniquely attributed to the stacking configurations whose interlayer binding energy breaks the C 2z symmetry on t...

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Bibliographic Details
Published in:Nano letters 2021-12, Vol.21 (23), p.10026-10031
Main Authors: Suri, Nishchay, Wang, Chong, Zhang, Yinhan, Xiao, Di
Format: Article
Language:English
Subjects:
Chemistry
Materials Science
Physics
Science & Technology - Other Topics
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Summary:We discover chiral phonons at the lowest energy bands in moiré superlattices. The moiré chiral phonons we uncover are the collective excitations of the stacking domains. Their origin is uniquely attributed to the stacking configurations whose interlayer binding energy breaks the C 2z symmetry on the moiré length scale. Within elastic theory, we use a general symmetry analysis to provide a complete classification of van der Waals heterostructures in respect to hosting moiré chiral phonons and show the calculation for twisted MoS2 as an example. We present a low-energy effective model to qualitatively understand the moiré chiral phonons and show that it captures the essential physics remarkably well. Our result potentially opens up new possibilities in phononic twistronics as the moiré chiral phonons have high tunability, moiré scale wavelengths, excitation energies in only a few meV and can possibly be mechanically excited.
ISSN:1530-6984
1530-6992
DOI:10.1021/acs.nanolett.1c03692