Observation of double-kink states in multivalley acoustic crystals

The Dirac degeneracy of band structures, along with the valley states after breaking, holds promising potential for robust signal processing. However, the conventional graphene structure only harbors a single pair of Dirac points, limiting its capacity for information storage and manipulation, and hindering its application in small-sized on-chip devices. In this study, we experimentally investigate S-graphene acoustic crystals that host two pairs of Dirac points and valleys. By examining the interplay between these multivalley pairs, we observe double-kink edge states that display $W$-type and $M$-type dispersions self-guiding at zigzag- and bearded boundaries in a single sample, respectively, eliminating the requirement of a cladding layer in conventional valley Hall effect. Additionally, benefiting from the increased degree of freedom, a superdirectional yet adjustable topological antenna is demonstrated by selectively exciting a specific valley branch. This research expands the degree of freedom for valleytronics and has the potential to stimulate the exploration of multiple spin-valley couplings and the design of unique functional devices.