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Spin-orbit interactions of transverse sound
Shubo Wang1, Guanqing Zhang2, Xulong Wang2
1Department of Physics, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong, China. shubwang@cityu.edu.hk.
Nature Communications
|October 22, 2021
Summary
This study demonstrates spin-orbit interactions (SOIs) in airborne sound using acoustic metamaterials. These findings enable new sound manipulation possibilities beyond conventional acoustics.
Area of Science:
- Acoustics
- Metamaterials
- Wave Physics
Background:
- Spin-orbit interactions (SOIs) are crucial in light, enabling phenomena like the photonic spin-Hall effect.
- Sound waves are typically longitudinal and lack intrinsic spin, making SOIs counterintuitive.
Purpose of the Study:
- To theoretically and experimentally demonstrate the existence of SOIs in airborne sound.
- To explore novel acoustic phenomena and functionalities enabled by artificial transversality in sound waves.
Main Methods:
- Utilizing an acoustic micropolar metamaterial to induce artificial transversality in sound.
- Investigating the coupling between acoustic spin and crystal momentum (k).
- Analyzing the scattering of transverse sound by dipole particles.
Main Results:
- Airborne sound was shown to possess artificial transversality, enabling it to carry spin and orbital angular momentum.
- Acoustic activity in the metamaterial induced spin-momentum coupling, resulting in negative refraction of transverse sound.
- Spin-dependent acoustic vortices were generated through geometric phase effects during scattering.
Conclusions:
- Acoustic SOIs are achievable in engineered metamaterials, expanding sound manipulation capabilities.
- This work opens new avenues for 'spin-orbit acoustics' and advanced sound control.
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