Realization of Topological Valley Hall Edge States of Elastic Waves in Phononic Crystals Based on Material Differences

In this study, the topological valley Hall edge states of elastic waves in phononic crystals are realized based on material differences. A phononic crystal structure with lantern rings is proposed. The results show that differences in the Young's modulus or density of lantern-ring materials can cause the destruction of the effective spatial inversion symmetry, which causes the valley Hall phase transition; thus, topological edge states emerge at the interface of two domains with topologically dissimilar phases. For valley topological transport, the traditional method to break the spatial inversion symmetry is by changing the dimensional parameters of scatterers in phononic crystals. However, in many cases, the space between scatterers is extremely small, making it difficult to obtain a sufficiently large band gap. Moreover, it is difficult to change the transport path and operating-frequency range of elastic waves after sample fabrication is finished. Here, the above problems are solved by the realization of valley topological transport based on changes to lantern-ring materials. The waveguide path is reconfigurable, that is, it can be altered conveniently, and the operating frequency can be tuned by changing the lantern-ring materials. These factors are very important for the topological transport of elastic waves. Topological valley transport achieved by this method has a good backscattering-suppression ability and obvious robustness to defects. Realization of topological valley Hall edge states by utilizing material differences provides an effective method for obtaining the topological transport of elastic waves, breaking the limitations of those based only on structural parameter changes, and this has good application prospects in elastic wave manipulation and communication.