Dual-band flexible large-area ultrasonic energy conveying via elastic chiral Landau levels

While conventional topological metamaterials offer promising avenues for manipulating elastic waves, energy capacities are commonly restricted from narrow structural boundaries or domain walls. The emergence of the chiral Landau level via introducing synthetic pseudomagnetic fields has been demonstrated to support unique bulk states, thereby spurring versatile wave controls. However, existing research primarily implements the chiral Landau level in a single frequency regime, impeding the applications of multiband functional devices. In this study, we realize the ultrasonic chiral Landau level of elastic waves in two separated frequency regions based on integrated topological valley phononic crystals. We demonstrate the chiral Landau level-induced dual-band bulk transport of ultrasonic waves with exceptional robustness against geometric perturbation, by numerical simulations and experiments. Remarkably, we achieve flexible ultrasonic energy manipulation including wave steering along an arbitrary route and energy splitting, through strategically tailoring the synthetic pseudomagnetic field in valley topological metamaterials. The developed topological elastic metamaterials with the dual-band chiral Landau levels functioning as extraordinary bulk states can find potential applications in multiband and multidirectional ultrasonic signal processing and energy management.