Robust and Reconfigurable Waveguide Design in Valley-Topological Phononic Crystals

As an analogy of topological insulators and superconductors, “topological phononics”, which applies the concept of band topology to acoustic dispersion, has attracted increasing attention in recent years. We present design of topological acoustic/elastic waveguides in phononic crystals. Topological waveguides are designed from the phonon dispersion analyses by finding edge modes appearing at interfaces between phononic crystals with different band topologies. As a prototype model, we first designed the topological waveguides in kHz regimes. Experimental validation of the designed waveguide has been performed in the frequency region via laser-doppler measurements. The robustness of the waveguide propagation against defects, corners, and structural inaccuracy in the waveguide has been quantitatively evaluated. We also introduced a structural transition of local symmetry inversion in the phononic crystal to implement a reconfigurability into the waveguide .Further development toward GHz regime will pave the way to the development of next-generation information devices using the proposed structures as an alternative or complimentary approach.