Selective excitation of localized acoustic skyrmion modes based on directional sound sources

Acoustic skyrmion modes are topological texture structures of velocity field vectors generated on the surface of acoustic structures. This protected vector distribution provides new dimensions for processing advanced sound information, transmission, and data storage. In this study, a combined structure of waveguides and spiral structures is designed by using directional acoustic sources to excite waveguide mode transmission, thereby achieving selective excitation of localized acoustic skyrmion modes. Through theoretical analysis and numerical simulations, the pressure field distribution and velocity field distribution excited by spin acoustic sources, Huygens acoustic sources, and Janus acoustic sources in this structure are investigated, demonstrating the directional transmission properties of acoustic surface waves and the selectively excited acoustic skyrmion modes in the combined structure. Numerical calculations reveal that when the spin acoustic source excites acoustic surface waves propagating along the waveguide, the acoustic skyrmion modes in the helical structure in the direction corresponding to the propagation are selectively excited. When the Huygens source excites acoustic surface waves propagating along the waveguide, the acoustic skyrmion modes in the right or left direction are selectively excited. However, when the Janus source excites acoustic surface waves propagating along the waveguide, the acoustic skyrmion modes in the upward or downward direction are selectively excited. This waveguide excitation method is a new means of exciting acoustic skyrmion modes, making the excitation of acoustic skyrmion modes more flexible. Moreover, this waveguide excitation method has significant potential applications in more complex and larger-scale acoustic systems. The research results may promote the understanding of the symmetry in acoustic near-field physics, open up new ways for manipulating particles by using sound waves, and also pave the way for designing advanced acoustic devices.