Anti-scattering propagation in multiple-bend valley phononic crystals

Valley topological phononic crystals (PCs) have attracted wide attention due to the topological properties of their edge states. In general, valley interface states can exist in the interfaces that are constructed by opposite valley topological phases. Here we study the anti-scattering propagation properties of edge states in a single valley PC. We present that the edge states can exist in different boundary terminations with different band dispersions. The boundary transport behaviors of acoustic waves along the two designed PCs are demonstrated numerically. The results show that the chiral edge states are immune against additional scatterers that preserve the valley pseudospins, but the backscattering can happen when intervalley scattering is included. Nevertheless, the anti-scattering propagation in complex multiple-bend structures can be realized by the smooth transition between the edge states and the valley interface states. Similar to the designed frequency-selective device, more prospective applications can be anticipated in the manipulation of acoustic wave propagation.