Coexistence of broadband conduction and amplitude-driven topological confinement in synthetic acoustic matter

Abstract

Nonlinear and topological wave phenomena offer new opportunities for robust wave manipulation. Existing experimental platforms have largely focused on on-site (Kerr-like) nonlinearities within tight-binding frameworks, leaving the regime of programmable nonlinear inter-site coupling in far-field scattering systems essentially unexplored. Here we demonstrate a programmable acoustic metamaterial that exhibits amplitude-driven topological confinement of sound while simultaneously maintaining broadband linear transmission across the same frequency range. The system consists of an open acoustic waveguide coupled to a chain of actively controlled electroacoustic resonators enabling tunable nonlinear and nonlocal interactions. Using a classical wave-scattering model we show that increasing the excitation amplitude drives a robust topological interface mode localized deep within the structure, with the confinement strengthening continuously with drive rather than at a finite threshold. The predictions are verified experimentally using a fully programmable metacrystal composed of individually controlled acoustic resonators, enabling real-time manipulation of coupling parameters. The mode's topological origin is established by symmetry: it survives coupling disorder beyond 50% of nominal but collapses when a delay between adjacent couplings is introduced, effectively breaking the protecting chiral symmetry. These results establish a versatile platform for studying nonlinear topological wave physics and for designing adaptive acoustic metamaterials.