Free-form acoustic topological waveguides enabled by topological lattice defects

The interplay between real-space topological lattice defects and momentum-space band topology can lead to new topological states. Here, the authors demonstrate that disclinations in acoustic valley-Hall crystals can induce valley-like transport. Using this mechanism, various acoustic topological waveguides with irregular shapes and multiple internal terminations are experimentally realized, providing a novel way for robust free-from waveguiding.