Acoustic metamaterials with spinning components

Abstract

We show that an acoustic metamaterial consisting of an array of spinning cylindrical inclusions can possess many unusual properties, including folded bulk bands and interface-state bands. The folding of bands inside the first Brillouin zone is made possible by a rotation-induced antiresonance of compressibility and the rotational Doppler effect. Both bulk and interface-state band dispersions exhibit remarkable filling-fraction-dependent features such as the emergence of a cutoff frequency when the filling fraction exceeds a critical value. Robust one-way transport properties are supported by nondegenerate interface states, but within the same band, interface states at different frequencies can have different propagation directions.