Imaging an Acoustic Topological Edge Mode on a Patterned Substrate with Microwave Impedance Microscopy

Abstract

The topological properties of an acoustic metamaterial's phononic band structure would be useful for developing functional acoustic and thermal devices. While previous demonstrations of topological properties have been limited to low-frequency airborne sound, high-frequency acoustic waveguides utilizing the topological edge state are increasingly in demand for quantum technologies, sensing, and microwave communication. In this work, the authors use innovative microscopy to visualize topological acoustic edge states at frequencies as high as 2.4 GHz on a patterned substrate, which bodes well for the feasibility of topological surface-acoustic-wave devices.