Multichannel Topological Transport in an Acoustic Valley Hall Insulator

Valley interface states, resulting in acoustic valley Hall topological insulators, have recently become a hot topic in the study of acoustic systems. On the basis of structural diversity and potential applications, we construct a two-dimensional triangular-lattice phononic crystal with ${C}_{3v}$-symmetric scatterers, and obtain two distinct valley Hall phases with nonvanishing valley Chern indices by rotating the scatterers. We numerically calculate the dispersion relations of these valley Hall phases including two kinds of interfaces, and find that valley interface states exist at not only the zigzag interface but also the armchair interface. We demonstrate the acoustic splitting and merging of valley interface states in the cross-waveguides, and numerically achieve the xor and or logic functions. We also design three complicated waveguides by assembling phononic crystals with distinct valley Hall phases. By experimental measurements in these waveguides, we successfully implement one-, two-, and three-channel topological transport. This research possibly provides a design route exploiting valley interface states to fabricate multichannel acoustic communication devices.