Realization of the Quantum Spin Hall Effect Using Tunable Acoustic Metamaterials

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We report pseudospin-dependent hybrid topological acoustic metamaterials constructed from tunable acoustic metamaterials and honeycomb-latticed sonic crystals. Using a theoretical model analogous to electrostatic interactions, we provide an efficient approach to evaluate intra- and interlattice couplings, whose competition is the major physical reason arousing the quantum spin Hall effect. The intralattice coupling is from the intrinsic design of the acoustic metamaterial, and the interlattice coupling is affected by multiple scattering among periodic scatterers. By independently manipulating the acoustic metamaterial and sonic crystal, we can successfully induce topological phase transitions at will. An alternative type of topological material is thus realized with great tunability. With identical building blocks for all hybrid topological acoustic metamaterials, a simple tuning of the corotation angle of each acoustic metamaterial can directly induce a topological phase transition, which makes the reconfiguration of the topological domains very convenient. A tunable multiport acoustic power divider is designed and demonstrated using numerical simulations and experiments. An alternative method to control the transmission rate and direction is thus reached and alternative routes for designing hybrid topological acoustic metamaterials with different functionalities and versatile applications are thus paved.