Double topological edge states investigation in sonic metamaterials

We investigate the topologically protected sound propagation in sonic metamaterials, analogous to quantum spin hall effect (QSHE). The sonic metamaterials consist of circular rods and meta-molecules arranged in air with a honeycomb-lattice. The on-demand inversion in topological phase can be achieved by two ways of scatterer controls at locally resonant frequency and Bragg frequency. The Helmholtz resonators in the structure are contributed to the formation of subwavelength double Dirac cones which are more likely to appear due to local resonance enhancement with more number of resonators. By combining two sonic metamaterials with different topological invariants, we demonstrate the robust sound propagation and pseudospin-dependent one-way acoustic propagation at the interface. Experimental measurement of the topologically protected acoustic wave transmission matches well with the simulation result. (C) 2020 Elsevier B.V. All rights reserved.