Elastic topological interface states induced by incident angle

Abstract

Topological interface states are currently attracting fast-growing attention in classical wave systems. However, little work has been done on the topological interface states in one-dimensional (1D) elastic wave systems, especially in the case of oblique incidence. This paper theoretically demonstrates the realization of topological interface states of elastic waves in a 1D composite structure composed of two phononic crystals (PCs) with different topological characteristics, which can be regulated by the incident angle. For the out-of-plane SH mode, multiple topological interface states can coexist in different common bandgaps. For the in-plane complex P-SV coupled mode, topological interface states can exist in both “partial-polarization” and “omni-polarization” bandgaps. All these topological interface states exist in wide incident angle regions. The polarization and the mode conversion of the interface states have also been discussed. Our results provide an innovative method to excite and tune topologically protected interface states for elastic waves, which may have potential applications in obtaining strong local vibration for different polarized elastic wave modes.