Experimental realization of a reconfigurable electroacoustic topological insulator

A substantial challenge in guiding elastic waves is the presence of reflection and scattering at sharp edges, defects, and dis-order. Recently, mechanical topological insulators have sought to overcome this challenge by supporting back-scattering resis-tant wave transmission. In this paper, we propose and experi-mentally demonstrate a reconfigurable electroacoustic topolog-ical insulator exhibiting an analog to the quantum valley Hall effect (QVHE). Using programmable switches, this phononic struc-ture allows for rapid reconfiguration of domain walls and thus the ability to control back-scattering resistant wave propaga-tion along dynamic interfaces for phonons lying in static and finite-frequency regimes. Accordingly, a graphene-like polyac-tic acid (PLA) layer serves as the host medium, equipped with periodically arranged and bonded piezoelectric (PZT) patches, resulting in two Dirac cones at the K points. The PZT patches are then connected to negative capacitance external circuits to break inversion symmetry and create nontrivial topologi-cally protected bandgaps. As such, topologically protected inter-face waves are demonstrated numerically and validated exper-imentally for different predefined trajectories over a broad frequency range.