Numerical and experimental evidence of topological edge states in periodic acoustic black hole based on valley hall effect

In this paper, we design a phononic crystal plate with periodic lattices based on acoustic black holes (ABHs). The basic structure is composed of a triangular lattice with ABHs in the x-y plane whose symmetry ensures that the Dirac cone exists at the corners of the Brillouin zone. The space inversion symmetry can be broken by alternating the parameter values of ABHs. Due to the symmetry of parameters, two topologically distinct phases can be obtained by analogy with the quantum valley Hall effect. We connect them together to create topological edge states. More specifically, the interface between these two phases supports the topologically protected elastic guided mode in the horizontal plane which features quasi-unidirectional propagation. Then, simulations and experiments are carried out to verify this phenomenon.