Observation of acoustic spin

• 作者: Chengzhi Shi Hong Chen Jie Ren Rongkuo Zhao Sui Yang Xiang Zhang Yang Long Yuan Wang
• 来源期刊: 国家科学评论（英文版）
• 年，卷（期）: 2019,（4）
• 页码范围: 707-712
• 页数: 6页
• 语种: 英文
• DOI: 10.1093/nsr/nwz059

摘要

Unlike optical waves, acoustic waves in fluids are described by scalar pressure fields, and therefore are considered spinless. Here, we demonstrate experimentally the existence of spin in acoustics. In the interference of two acoustic waves propagating perpendicularly to each other, we observed the spin angular momentum in free space as a result of the rotation of local particle velocity. We successfully measured the acoustic spin, and spin-induced torque acting on a designed lossy acoustic probe that results from absorption of the spin angular momentum. The acoustic spin is also observed in the evanescent field of a guided mode traveling along a metamaterial waveguide. We found spin–momentum locking in acoustic waves whose propagation direction is determined by the sign of spin. The observed acoustic spin could open a new door in acoustics and its applications for the control of wave propagation and particle rotation.