被动$\mathcal{PT}$对称Willis介质中的单向零声反射
Unidirectional zero sonic reflection in passive $\mathcal{PT}$ symmetric Willis media
摘要：
在声学超材料的有效介质描述中，Willis耦合与电磁学中的双各向异性具有相同的作用。Willis介质可以用一个由经典的有效体积模量和密度以及定义声学双各向异性的附加交叉耦合项组成的本构矩阵来描述。基于一个统一的理论模型，我们统一的属性的声学威利斯耦合与$\mathcal{PT}$对称系统在同一把伞下，并显示在任何一种情况下，一个例外的点主机一个非常明显的散射不对称性，伴随着单向零反射声波。分析处理支持实验输入的非对称侧载wavesguides显示如何规范转换和损失偏置可以拥抱威利斯材料和非厄米物理量身定制单向无反射声学，这是有目的的隔音和转向。
英文摘要：
In an effective medium description of acoustic metamaterials, the Willis coupling plays the same role as the bianisotropy in electromagnetism. Willis media can be described by a constitutive matrix composed of the classical effective bulk modulus and density and additional cross-coupling terms defining the acoustic bianisotropy. Based on an unifying theoretical model, we unite the properties of acoustic Willis coupling with $\mathcal{PT}$ symmetric systems under the same umbrella and show in either case that an exceptional point hosts a remarkably pronounced scattering asymmetry that is accompanied by one-way zero reflection for sound waves. The analytical treatment is backed up by experimental input in asymmetrically side-loaded wavesguides showing how gauge transformations and loss biasing can embrace both Willis materials and non-Hermitian physics to tailor unidirectional reflectionless acoustics, which is appealing for purposeful sound insulation and steering.
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