Synthetic Pseudo-Spin-Hall effect in acoustic metamaterials

Matthew Weiner; Xiang Ni; Andrea Alù; Alexander B Khanikaev

doi:10.1038/s41467-022-34072-4

Synthetic Pseudo-Spin-Hall effect in acoustic metamaterials

Nat Commun. 2022 Oct 25;13(1):6332. doi: 10.1038/s41467-022-34072-4.

Authors

Matthew Weiner^{1

2

3

4}, Xiang Ni^{1

2

5}, Andrea Alù^{1

2

5}, Alexander B Khanikaev^{6

7

8}

Affiliations

¹ Department of Electrical Engineering, Grove School of Engineering, City College of the City University of New York, New York, NY, USA.
² Physics Program, Graduate Center of the City University of New York, New York, NY, USA.
³ Department of Physics, City College of New York, New York, NY, USA.
⁴ Nokia Bell Labs, New Providence, NJ, USA.
⁵ Advanced Science Research Center, City University of New York, New York, NY, USA.
⁶ Department of Electrical Engineering, Grove School of Engineering, City College of the City University of New York, New York, NY, USA. akhanikaev@ccny.cuny.edu.
⁷ Physics Program, Graduate Center of the City University of New York, New York, NY, USA. akhanikaev@ccny.cuny.edu.
⁸ Department of Physics, City College of New York, New York, NY, USA. akhanikaev@ccny.cuny.edu.

Abstract

While vector fields naturally offer additional degrees of freedom for emulating spin, acoustic pressure field is scalar in nature, and it requires engineering of synthetic degrees of freedom by material design. Here we experimentally demonstrate the control of sound waves by using two types of engineered acoustic systems, where synthetic pseudo-spin emerges either as a consequence of the evanescent nature of the field or due to lattice symmetry. First, we show that evanescent sound waves in perforated films possess transverse angular momentum locked to their propagation direction which enables their directional excitation. Second, we demonstrate that lattice symmetries of an acoustic kagome lattice also enable a synthetic transverse pseudo-spin locked to the linear momentum, enabling control of the propagation of modes both in the bulk and along the edges. Our results open a new degree of control of radiation and propagation of acoustic waves thus offering new design approaches for acoustic devices.