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.

沿表面引导的弹性波在地球物理，超声检查，机械振动和表面声波设备中占主导地位。精确控制表面瑞利波及其与极化体波的耦合提出了一个挑战，即要解锁有效的能量收集和减振设备所需的波传输灵活性。我们设计了弹性的超表面，它由附着在弹性基底上的杆谐振器的渐变阵列组成，再加上声子-电子系统中Umklapp散射的关键见解，使我们能够利用晶体动量的传递。我们将瑞利表面波模转换为形成可调谐光束的体波。实验，