Acoustic Valley Spin Chern Insulators

The valley topological phases and transport phenomena for classical waves have attracted a great deal of attention. We realize valley spin Chern insulators in bilayer phononic crystals of a square lattice, whose topological invariants are described by the valley spin Chern numbers with the layer pseudospin. Four types of nontrivial topological phases can be realized by tuning the heights of cavities, which can result in the layer-mixed, layer-polarized, and layer-locked acoustic kink states. Interestingly, we experimentally demonstrate the anomalous layer-dependent partition transports of the acoustic kink states at the intersection constituted by the distinct topological phases. By taking advantage of the additional layer pseudospin, our systems provide a powerful platform from which to explore the intriguing properties of topological acoustics, and have potential applications for sound manipulation.