Broadband topological valley-projected edge-states transport in composite structure phononic crystal* *Project supported by the National Natural Science Foundation of China (Grant No. 61775050) and the Fundamental Research Funds for the Central Universities, China (Grant No. PA2019GDZC0098).

Abstract

The topological valley transport, realized in phononic crystals, has aroused tremendous interest in these years. Many previous researches have further promoted the development of this transport phenomenon. Crucially, the bandwidth of the valley-projected edge mode has been an essential research topic. As is well known, the broadband will improve the adaptability of the acoustic edge-states, which will be more conducive to the transmission of information. Therefore, in this paper, we present a composite structure, composed of the atoms with different shapes forming a hexagonal lattice, which can achieve larger bandwidth than a single structure. Meanwhile, the results demonstrate that the topological protected edge states are also observed in our structure. Furthermore, the backscattering suppressions from associated valley-protected edge states under certain perturbations have also been investigated and demonstrated. Our work can provide a new idea for designing acoustic devices based on valley degree of freedom.