Tailored elastic surface to body wave Umklapp conversion

Public Time: 2020-06-29 00:00:00
Journal: Nature Communications
doi: 10.1038/s41467-020-17021-x
Author: Gregory J. Chaplain;Jacopo M. De Ponti;Andrea Colombi;Rafael Fuentes-Dominguez;Paul Dryburg;Don Pieris;Richard J. Smith;Adam Clare;Matt Clark;Richard V. Craster
Summary: Elastic waves guided along surfaces dominate applications in geophysics, ultrasonic inspection, mechanical vibration, and surface acoustic wave devices; precise manipulation of surface Rayleigh waves and their coupling with polarised body waves presents a challenge that offers to unlock the flexibility in wave transport required for efficient energy harvesting and vibration mitigation devices. We design elastic metasurfaces, consisting of a graded array of rod resonators attached to an elastic substrate that, together with critical insight from Umklapp scattering in phonon-electron systems, allow us to leverage the transfer of crystal momentum; we mode-convert Rayleigh surface waves into bulk waves that form tunable beams. Experiments, theory and simulation verify that these tailored Umklapp mechanisms play a key role in coupling surface Rayleigh waves to reversed bulk shear and compressional waves independently, thereby creating passive self-phased arrays allowing for tunable redirection and wave focusing within the bulk medium.
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