Topological Sliding Moiré Phononic Crystals

Topological physics in classical systems, such as photonic and acoustic systems, is fast becoming an exciting field in fundamental and applied research. However, almost all existing topological acoustic materials are restricted to systems with conventional lattices and specific time-space symmetries. Here, we present a unique design of topological phononic crystals with moiré superlattice that are constructed by simply sliding a layer of moiré phononic crystals. Assisted by the sliding degree of freedom, sliding moiré phononic crystals exhibit nontrivial topology characterized by a dynamical Chern number, leading to topological pumping of special topological moiré edge states that are completely insensitive to the edge geometry. More interestingly, moiré phononic crystals possess one-dimensional moiré flat bulk bands, giving rise to one-dimensional localized states in the bulk that result in an array of compact and nearly independent one-dimensional signal channels. Various applications such as acoustic communications and isolations in integrated devices can be anticipated from the intriguing acoustic one-dimensional localized bulk states and topological moiré edge states enriched by the sliding modulation.