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Ultrasonic crystals provide a novel path forward for studying Dirac-like physics in classical systems free from interaction effects and are considered promising candidates for the development of more complex multilayer systems, such as those governed by a Moire pattern. However, no ultrasonic crystal experiment (and to the best of our knowledge no experiment studying classical wave propagation in a hexagonal lattice) has measured linear dispersion along the Dirac cone at the edge of the Brillouin zone where the upper and lower bands touch, which must include a measure of reduced phase and group velocities along the cone. This presentation will discuss experimental and theoretical results on acoustic surface wave propagation in a hexagonal lattice of resonant cavities, which can aid in the observation of such Dirac-like physics for ultrasonic crystals.
Gangemi et al. (Fri,) studied this question.