The topological one-way waveguide mode of the acoustic wave has recently been demonstrated in various meta-structure systems. Here, we show that in a topological phononic crystal with a symmetry-broken acoustic unit cell, the topological state possesses not just a “spin-like” pseudospin mode but also real spin angular momentum. By rotating the double-square units, the band of the phononic crystal will become inverse and induce both topological phase transition and spin angular momentum reversal. As such, by putting two topologically different systems together, the spin angular momentum dependent one-way interface modes can be selectively excited by acoustic spin sources, exhibiting robust transport protected by tight spin-momentum locking. The spin angular momentum density distribution in the unit cell and edge states shows that in addition to the pseudospin, there is a strong correlation between the real spin angular momentum and topological properties in this acoustic system, producing the topologically selective acoustic torque. Revealing the real spin angular momentum and associated acoustic spin torque properties of these topological phononic and acoustic systems will give people a more general understanding about symmetric breaking wave systems and help people to explore more potential applications of acoustic spins in various topological systems.
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7 April 2021
Research Article|
April 02 2021
Real spin angular momentum and acoustic spin torque in a topological phononic crystal
Special Collection:
Acoustic Metamaterials 2021
Chenwen Yang
;
Chenwen Yang
Center for Phononics and Thermal Energy Science, China-EU Joint Lab on Nanophononics, Shanghai Key Laboratory of Special Artificial Microstructure Materials and Technology, School of Physics Science and Engineering, Tongji University
, 200092 Shanghai, China
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Yu-Tao Tan
;
Yu-Tao Tan
Center for Phononics and Thermal Energy Science, China-EU Joint Lab on Nanophononics, Shanghai Key Laboratory of Special Artificial Microstructure Materials and Technology, School of Physics Science and Engineering, Tongji University
, 200092 Shanghai, China
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Hong Chen;
Hong Chen
Center for Phononics and Thermal Energy Science, China-EU Joint Lab on Nanophononics, Shanghai Key Laboratory of Special Artificial Microstructure Materials and Technology, School of Physics Science and Engineering, Tongji University
, 200092 Shanghai, China
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Jie Ren
Jie Ren
a)
Center for Phononics and Thermal Energy Science, China-EU Joint Lab on Nanophononics, Shanghai Key Laboratory of Special Artificial Microstructure Materials and Technology, School of Physics Science and Engineering, Tongji University
, 200092 Shanghai, China
a)Author to whom correspondence should be addressed: Xonics@tongji.edu.cn
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a)Author to whom correspondence should be addressed: Xonics@tongji.edu.cn
Note: This paper is part of the Special Topic on Acoustic Metamaterials 2021.
J. Appl. Phys. 129, 135106 (2021)
Article history
Received:
December 31 2020
Accepted:
March 09 2021
Citation
Chenwen Yang, Yu-Tao Tan, Hong Chen, Jie Ren; Real spin angular momentum and acoustic spin torque in a topological phononic crystal. J. Appl. Phys. 7 April 2021; 129 (13): 135106. https://doi.org/10.1063/5.0042556
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