Acoustic Weyl semimetals in synthetic dimensions

Here, we propose the construction of acoustic Weyl semimetals in synthetic dimensions based on a 2D coupling waveguide array under external dynamic modulations. The type-I, type-II, and line node acoustic Weyl semimetals can be realized in one lattice array and the associated transitions between different phases can be implemented by flexibly adjusting the dynamic modulations. The correspondence between different phases and symmetries is analyzed. The results clearly show that the spectra of topological surface states undergo bidirectional or unidirectional shifts in the frequency domain according to the type of Weyl points. Our work opens the door for studying acoustic Weyl physics in the synthetic dimensions and may have impacts on acoustic wave manipulation in both spatial and frequency domains.