Topological energy harvesting of surface acoustic waves in a phononic crystal slab with periodic stubbed surface

In this paper, we demonstrate energy harvesting of surface acoustic waves (SAWs) via topological interface states in a two-dimensional phononic crystal (PC) with the periodic arrangement of bar-like locally resonant units on its surface. The system can produce pure SAW bands in the subwavelength realm due to bar oscillation. Both transverse and longitudinal vibrations of the stubbed bar can selectively couple to the intrinsic SAWs in the PC slab. Subsequently, through constructing the typical Su-Schrieffer-Heeger model, we analyze the topological properties of zone-folding-induced SAW bands with transverse and longitudinal vibration characteristics, respectively. When two arrays with distinct topological bandgaps are spliced together, topological interface states will appear. Topological energy harvesting of SAWs with two different vibration characteristics is finally achieved in one structure. Our study expands the applicability of topological interface states for SAW in a compacted platform, such as polarization selection or sensing.