Active Metamaterials with Negative Static Electric Susceptibility

Abstract

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.

Monitoring variations of refractive index via Hilbert–Schmidt speed and applying this phenomenon to improve quantum metrology

“…However, natural materials with negative values of both ϵ and µ are rare and only exist at certain frequency ranges. Therefore, researchers have explored alternative ways to achieve negative refraction, such as using materials with only one negative parameter (either ϵ or õ) [32][33][34][35][36][37], or using composite structures that combine different materials with positive and negative parameters. In this paper, we investigate how QFI and Hilbert-Schmidt speed (HSS), two important quantum metrological tools [10], can be used to detect and characterize these phenomena in atomic media with nonlinear optical responses.…”