Active Metamaterials with Negative Static Electric Susceptibility.
Active Metamaterials with Negative Static Electric Susceptibility.
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具有负静电敏感性的活性超材料。
DOI：
10.1002/adma.201904863
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发表时间：
2020
期刊：
影响因子：
--
通讯作者：
Castles F
中科院分区：
文献类型：
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作者：
Castles F
虽然教科书上的论点认为静电磁化率χ（0）在“所有物体”中必须是正的，但有人指出，不处于热力学平衡的材料不一定受此限制。具有反转的原子和分子能级布居的介质在理论上已经被预测为表现出X（0）< 0状态，然而所设想的系统需要降低的温度、降低的压力和外部泵浦激光器来维持布居反转。此外，χ（0）< 0的存在从未被实验证实。在这里，一个完全不同的方法来解决问题的χ（0）< 0，并提出了一种设计概念，以实现“真正的”χ（0）< 0的基础上，有源超材料与内部电源。制造两种有源超材料结构，尽管出于实际方便的原因，它们仍然具有外部实现的电源，但它们提供了支持一般概念的证据。有效值在室温和常压下很容易获得，并且在稳定性−1 <x（0）< 0的范围内是可调的，从而导致实验确定的幅度比先前预测的大一千倍以上。由于χ（0）< 0是抗磁性的缺失电模拟，这项工作为稳定的静电悬浮等新技术能力打开了大门。
Although well‐established textbook arguments suggest that static electric susceptibility χ(0)must be positive in “all bodies,” it has been pointed out that materials that are not in thermodynamic equilibrium are not necessarily subject to this restriction. Media with inverted populations of atomic and molecular energy levels have been predicted theoretically to exhibit a χ(0)< 0 state, however the systems envisioned require reduced temperature, reduced pressure, and an external pump laser to maintain the population inversion. Further, the existence of χ(0)< 0 has never been confirmed experimentally. Here, a completely different approach is taken to the question of χ(0)< 0 and a design concept to achieve “true” χ(0)< 0 is proposed based on active metamaterials with internal power sources. Two active metamaterial structures are fabricated that, despite still having their power sources implemented externally for reasons of practical convenience, provide evidence in support of the general concept. Effective values are readily achieved at room temperature and pressure and are tunable throughout the range of stability −1 < χ(0)< 0, resulting in experimentally‐determined magnitudes that are over one thousand times greater than those predicted previously. Since χ(0)< 0 is the missing electric analog of diamagnetism, this work opens the door to new technological capabilities such as stable electrostatic levitation.