Subwavelength Acoustic Valley-Hall Topological Insulators Using Soda Cans Honeycomb Lattices

摘要

Topological valley-contrasting physics has attracted great attention in exploring the use of the valley degree of freedom as a promising carrier of information.Recently,this concept has been extended to acoustic systems to obtain nonbackscattering sound propagations.However,previous demonstrations are limited by the cut-off frequency of 2D waveguides and lattice-scale size restrictions since the topological edge states originate from Bragg interference.Here we engineer topologically valley-projected edge states in the form of spoof surface acoustic waves that confine along the surface of a subwavelength honeycomb lattice composed of 330-mL soda cans.The inversion symmetry is broken through injecting a certain amount of water into one of the two cans in each unit cell,which gaps the Dirac cone and ultimately leads to the topological valley-Hall phase transition.Dual-frequency ranges of the valley-projected edge states below the sound line are observed,which originate from the first-order and second-order resonances,respectively.These results have the potential to enable promising routes to design integrated acoustic devices based on valley-contrasting physics.