Observation of acoustic spin

Chengzhi Shi, Rongkuo Zhao, Yang Long, Sui Yang, Yuan Wang, Hong Chen, Jie Ren, Xiang Zhang

Research output: Contribution to journalArticlepeer-review

89 Scopus citations


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.

Original languageEnglish (US)
Pages (from-to)707-712
Number of pages6
JournalNational Science Review
Issue number4
StatePublished - Jul 1 2019
Externally publishedYes


  • acoustic spin
  • spin-induced torque
  • spin-momentum locking

ASJC Scopus subject areas

  • General


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