Spin-orbit interactions of transverse sound
arXiv:2105.13558 · doi:10.1038/s41467-021-26375-9
Abstract
Spin-orbit interactions (SOIs) endow light with intriguing properties and applications such as photonic spin-Hall effects and spin-dependent vortex generations. However, it is counterintuitive that SOIs can exist for sound, which is a longitudinal wave that carries no intrinsic spin. Here, we theoretically and experimentally demonstrate that airborne sound can possess artificial transversality in an acoustic micropolar metamaterial and thus carry both spin and orbital angular momentum. This enables the realization of acoustic SOIs with rich phenomena beyond those in conventional acoustic systems. We demonstrate that acoustic activity of the metamaterial can induce coupling between the spin and linear crystal momentum k, which leads to negative refraction of the transverse sound. In addition, we show that the scattering of the transverse sound by a dipole particle can generate spin-dependent acoustic vortices via the geometric phase effect. The acoustic SOIs can provide new perspectives and functionalities for sound manipulations beyond the conventional scalar degree of freedom and may open an avenue to the development of spin-orbit acoustics.
31 pages, 8 figures
References in corpus (9)
- Optical spin-to-orbital angular momentum conversion in inhomogeneous anisotropic media
- Chiral nanophotonic waveguide interface based on spin-orbit coupling of light
- Valley Vortex States in Sonic Crystals
- Spin and orbital angular momenta of acoustic beams
- Topological non-Hermitian origin of surface Maxwell waves
- Transverse spin and surface waves in acoustic metamaterials
- Polar metamaterials: A new outlook on resonance for cloaking applications
- A group theoretical route to deterministic Weyl points in chiral photonic lattices
- Optical isolation induced by subwavelength spinning particle via spin-orbit interaction