论文标题

声学威利斯超材料超出被动性

Acoustic Willis metamaterials beyond the passivity bound

论文作者

Cho, Choonlae, Wen, Xinhua, Park, Namkyoo, Li, Jensen

论文摘要

声学双性异性(也称为Willis参数)通过在组成关系中的动量和应变之间提供非惯性耦合来扩展声学领域。与电磁学共享共同的基础,声学双歧镜的实现可以与适当设计的逆散装模量和质量密度合作对声波进行异国情调操纵。尽管整个本构参数的控制证实了有趣的理论和实用应用,但尚未开发出独立和精确设计的极化能力的Willis超材料,以克服最大威利斯结合的最大限制以及对变质剂的被动性固有的非质量限制。在这里,通过扩展了最近开发的虚拟化超材料的概念,我们提出了打破了被动性和相互限制的声学威利斯超材料,同时还可以实现对所有具有设计频率响应的本构参数的解耦控制。通过基于每种极化响应的平均对称性对称对称性的基础卷积内核,我们在实验中证明了双异常的被动培养基极限。此外,还基于数字卷积的频率分散的反向设计概念,还证明了纯粹的非偏置媒体和具有宽带,平坦响应威利斯耦合的媒体。我们的方法提供了在因果关系条件下可访问的所有可能独立可编程的极端本构参数和频率色散可调性,并为实现声学超材料的完整功能提供了一个灵活的平台。

Acoustic bianisotropy, also known as the Willis parameter, expands the field of acoustics by providing nonconventional couplings between momentum and strain in constitutive relations. Sharing the common ground with electromagnetics, the realization of acoustic bianisotropy enables the exotic manipulation of acoustic waves in cooperation with a properly designed inverse bulk modulus and mass density. While the control of entire constitutive parameters substantiates intriguing theoretical and practical applications, a Willis metamaterial that enables independently and precisely designed polarizabilities has yet to be developed to overcome the present restrictions of the maximum Willis bound and the nonreciprocity inherent to the passivity of metamaterials. Here, by extending the recently developed concept of virtualized metamaterials, we propose acoustic Willis metamaterials that break the passivity and reciprocity limit while also achieving decoupled control of all constitutive parameters with designed frequency responses. By instituting basis convolution kernels based on parity symmetry for each polarization response, we experimentally demonstrate bianisotropy beyond the limit of passive media. Furthermore, based on the notion of inverse design of the frequency dispersion by means of digital convolution, purely nonreciprocal media and media with a broadband, flat-response Willis coupling are also demonstrated. Our approach offers all possible independently programmable extreme constitutive parameters and frequency dispersion tunability accessible within the causality condition and provides a flexible platform for realizing the full capabilities of acoustic metamaterials.

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