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.

中文翻译：

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具有负静电敏感性的活性超材料。

尽管公认的教科书论点表明，静电敏感性χ（0）在“所有物体”中必须为正，但已指出，未处于热力学平衡状态的材料不必受此限制。从理论上预测具有原子和分子能级倒数的介质将表现出χ（0）<0状态，但是所设想的系统需要降低温度，降低压力和外部泵浦激光器来保持粒子数反转。而且，从未通过实验证实χ（0）<0的存在。在这里，对χ（0）<0采取完全不同的方法，并基于带有内部电源的有源超材料，提出了实现“真”χ（0）<0的设计概念。制造了两个有源超材料结构，尽管出于实用方便的原因仍在外部实现了其动力源，但仍提供了支持这一总体概念的证据。有效值可以在室温和压力下轻松获得，并且可以在整个稳定性范围-1 <χ（0）<0范围内调节，从而导致实验确定的幅度比先前预测的幅度大一千倍。由于χ（0）<0是缺少的反磁性电模拟物，因此这项工作为新技术能力（例如稳定的静电悬浮）打开了大门。有效值可以在室温和压力下轻松获得，并且可以在整个稳定性范围-1 <χ（0）<0范围内调节，从而导致实验确定的幅度比先前预测的幅度大一千倍。由于χ（0）<0是缺少的反磁性电模拟物，因此这项工作为新技术能力（例如稳定的静电悬浮）打开了大门。有效值可以在室温和压力下轻松获得，并且可以在整个稳定性范围-1 <χ（0）<0范围内调节，从而导致实验确定的幅度比先前预测的幅度大一千倍。由于χ（0）<0是缺少的反磁性电模拟物，因此这项工作为新技术能力（例如稳定的静电悬浮）打开了大门。