Topological sonic whispering gallery protected by the synthetic Weyl points

The synthetic dimensional provides a powerful platform for us to explore the topological properties of matter. In this paper, we choose two physical dimensions ($k_x$ and $k_y$) and one geometric structure parameter (the height of the air cavity $\delta$) to construct a synthetic space. The simulation results display that the three couples of Weyl points and Fermi arcs appear in the synthetic space. We find that the frequency range of valley chiral edge states can be flexibly regulated by changing the position of boundary truncation of the sonic crystal. Both theoretically and experimentally, we demonstrate that the sonic valley-locked whispering gallery can be realized along the interface between the sonic crystals and hard walls. In the valley-locked whispering gallery, the acoustic waves propagate unidirectionally along the closed channel, with highly scattering efficiency and small diffraction.