Causality of linear time-invariant systems inherently defines the wave-matter interaction process in wave physics. This principle imposes strict constraints on the interfacial response of materials on various physical platforms. A typical consequence is that a delicate balance has to be struck between the conflicting bandwidth and geometric thickness when constructing a medium with desired impedance, which makes it challenging to realize broadband impedance modulation with compact structures. In pursue of improvement, the over-damped recipe and the reduced excessive response recipe are creatively presented in this work. As proof-of-concept demonstration, we construct a metamaterial with intensive mode density which supports strong non-locality over a frequency band from 320 Hz to 6400 Hz. Under the guidelines of the over-damped recipe and the reduced excessive response recipe, the metamaterial realizes impedance matching to air and exhibits broadband near-perfect absorption without evident impedance oscillation and absorption dips in the working frequency band. We further present a dual-functional design capable of frequency-selective absorption and reflection by concentrating the resonance modes in three frequency bands. Our research reveals the significance of the over-damped recipe and the strong non-local effect in broadband impedance modulation, which may open up avenues for constructing efficient artificial impedance boundaries for energy absorption and other wave manipulation.

中文翻译：

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通过非局部声学超材料进行宽带阻抗调制

线性时不变系统的因果关系固有地定义了波物理学中的波物质相互作用过程。该原理对材料在各种物理平台上的界面响应施加了严格的限制。一个典型的后果是，在构建具有所需阻抗的介质时，必须在冲突的带宽和几何厚度之间取得微妙的平衡，这使得实现具有紧凑结构的宽带阻抗调制具有挑战性。为了追求改进，本作品创造性地提出了过阻尼配方和减少过度响应配方。作为概念验证演示，我们构建了一种具有密集模式密度的超材料，该材料在 320 Hz 至 6400 Hz 的频带上支持强非局部性。在过阻尼配方和减少过度响应配方的指导下，超材料实现了与空气的阻抗匹配，并表现出宽带近乎完美的吸收，在工作频段没有明显的阻抗振荡和吸收下降。我们进一步提出了一种双功能设计，能够通过将共振模式集中在三个频带中来进行频率选择性吸收和反射。我们的研究揭示了过阻尼配方的重要性和宽带阻抗调制中的强非局部效应，这可能为构建有效的人工阻抗边界以进行能量吸收和其他波操纵开辟道路。超材料实现了与空气的阻抗匹配，并表现出宽带近乎完美的吸收，在工作频段没有明显的阻抗振荡和吸收下降。我们进一步提出了一种双功能设计，能够通过将共振模式集中在三个频带中来进行频率选择性吸收和反射。我们的研究揭示了过阻尼配方的重要性和宽带阻抗调制中的强非局部效应，这可能为构建有效的人工阻抗边界以进行能量吸收和其他波操纵开辟道路。超材料实现了与空气的阻抗匹配，并表现出宽带近乎完美的吸收，在工作频段没有明显的阻抗振荡和吸收下降。我们进一步提出了一种双功能设计，能够通过将共振模式集中在三个频带中来进行频率选择性吸收和反射。我们的研究揭示了过阻尼配方的重要性和宽带阻抗调制中的强非局部效应，这可能为构建有效的人工阻抗边界以进行能量吸收和其他波操纵开辟道路。