The topological properties of an object, associated with an integer called the topological
invariant, are global features that cannot change continuously but only through abrupt …

Acoustic metamaterials have been widely investigated over the past few decades and have
realized acoustic parameters that are not achievable using conventional materials. After …

The book provides a comprehensive presentation of the topic of phononic and sonic
crystals, including acoustic and elastic wave propagation in homogeneous and periodic …

Nontrivial band topologies have been discovered in classical systems and hold great
potential for device applications. Unlike photons, sound has fundamentally different …

Strongly confined waveguiding is one of the main applications of phononic crystals that can
be achieved at any frequency and scale. Phononic crystal waveguides replace the cladding …

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 …

Previous studies on the propagation direction of valley topological edge states mainly focus
on the matching between orbital angular momentum of the excitation source and specific …

In this work, we construct on-chip valley phononic crystal plates by building up triangular
silicon pillars on the silicon plate. We introduce the graded interface sliding for two typical …

Originally discovered in condensed matter systems, topological insulators (TIs) have been
ubiquitously extended to various fields of classical wave physics including photonics …

Topological insulators that can host special symmetry-protected boundary states and corner
states have attracted increasing intention in acoustic engineering. Recently, the concept of …