Multiplexed chiral and helical acoustic anomaly bulk states in an inverse-designed metamaterial

However, they have so far been realized mostly in separate systems. Here, we achieve the multiplexing of valley and pseudospin DOFs in one acoustic system.

An acoustic metamaterial simultaneously hosting single and double Dirac cones is inversely designed by the developed topology optimization method. Thereafter, under a hard-boundary condition, valley-locked chiral states and pseudospin-locked helical states emerge within two separate frequency windows and can be selected by tuning the operating frequency. Furthermore, their applications for multifrequency acoustic energy enhancement are experimentally demonstrated.