Robust and High-Capacity Phononic Communications through Topological Edge States by Discrete Degree-of-Freedom Multiplexing

One long-term goal of phononic communications is to achieve the controlled transport of elastic wave signals with enhanced information capacity and improved robustness, which is still challenging given the complexity of elastic waves in terms of vectorial movement and multiple polarizations. Here, we present our theoretical and experimental study of the robust transport of elastic wave signals along interfaces between distinct topological phases. These topological edge states are robust against defects and disorders because they are jointly protected by both pseudospin and valley degrees of freedom (DOFs); thus naturally providing doubled information carriers within a single channel. A topology-based beam splitter is experimentally demonstrated, where the signal's propagation path is uniquely determined and topologically protected. Edge states between distinct topological phases not only offer a route towards new topological phenomena, but also open up an avenue for the design of high-capacity and robust phononic communication devices through discrete DOF multiplexing.