Directional Acoustic Superscattering by Coupled Resonators

We demonstrate acoustic superscattering from a subwavelength scatterer consisting of multiple deep-subwavelength resonators. We show that superscattering is enabled by strong coupling between these resonators and the discrete rotational symmetry of the scatterer results in angle-dependent superscattering. From the cylindrical-wave expansion of an incident plane wave, we observe that radially arranged resonators can effectively couple to these expanded cylindrical waves. In addition, we provide an analytical model characterizing the coupled resonators, providing a critical understanding of superscattering. As an experimental demonstration, we present a superscatterer with six acoustic resonators that shows angle-dependent superscattering.