Rayleigh wave metasurface with the emerging hybrid band characteristics of Auxetic metamaterials

This paper introduces a novel metasurface based on Auxetic metamaterials for attenuating and isolating low-frequency Rayleigh waves. Distributed scatterers are embedded in the Auxetic substrate to form the unit cell, and the meticulously designed layout is intended to induce more multipolar resonance modes. Firstly, the propagation characteristics of Rayleigh waves in the elastic half-space containing metamaterial domain are investigated under the dynamic effective framework of elastic media, and the effective parameter combinations for shielding Rayleigh waves are summarized, which provide a guide for customized design. Then, a new ultra-low frequency band gap is revealed via eigenstate analysis and effective parameter calculation. More noteworthy is the discovery of bridging effects in hybrid bands. Finally, multiple bandgaps, including ultra-low frequency bandgap, are integrated through hybrid bands, achieving an ultra-wide attenuation from 3.2 Hz to 20 Hz, almost perfectly covering the main frequency range of real seismic Rayleigh waves. At the same time, a reduction of up to 96.3% in the response peak is also validated in time-domain testing. More promisingly, there is still room to improve the low-frequency performance of the metasurface by optimizing the effective modulus of the Auxetic metamaterial. Undoubtedly, it further explores the physical boundary of extremely compact metamaterials in modulating even larger wavelength, which will inspire more potential Auxetic metamaterials for applications in emerging fields.