The physics and applications of superconducting metamaterials

Abstract

We summarize progress in the development and application of metamaterial structures utilizing superconducting elements. After a brief review of the salient features of superconductivity, the advantages of superconducting metamaterials over their normal metal counterparts are discussed. We then present the unique electromagnetic properties of superconductors and discuss their use in both proposed and demonstrated metamaterial structures.Finally we discuss novel applications enabled by superconducting metamaterials, and then mention a few possible directions for future research.Our objective is to give a basic introduction to the emerging field of superconducting metamaterials. The discussion will focus on the RF, microwave, and low-THz frequency range, because only there can the unique properties of superconductors be utilized. Superconductors have a number of electromagnetic properties not shared by normal metals, and these properties can be exploited to make nearly ideal and novel metamaterial structures. In section I. we begin with a brief overview of the properties of superconductors that are of relevance to this discussion. In section II we consider some of the shortcomings of normal metal based metamaterials, and discuss how superconducting versions can have dramatically superior properties. This section also covers some of the limitations and disadvantages of superconducting metamaterials. Section III reviews theoretical and experimental results on a number of unique metamaterials, and discusses their properties.Section IV reviews novel applications of superconducting metamaterials, while section V includes a summary and speculates about future directions for these metamaterials. I. SuperconductivitySuperconductivity is characterized by three hallmark properties, these being zero DC resistance, a fully diamagnetic Meissner effect, and macroscopic quantum phenomena. 1 , 2 , 3 The zero DC resistance hallmark was first discovered by Kamerlingh Onnes in 1911, and has since led to many important applications of superconductors in power transmission and energy storage. The second hallmark is a spontaneous and essentially complete diamagnetic response developed by superconductors in the presence of a static magnetic field. As the material enters the superconducting state it will develop currents to exclude magnetic field from its interior. This phenomenon is known as the Meissner effect, and distinguishes superconductors from perfect conductors (which would not show a spontaneous Meissner effect).Finally, macroscopic quantum effects arise from the quantum mechanical nature of the superconducting correlated electron state.

Multistability and switching in a superconducting metamaterial

“…I n recent years, the idea of using superconducting quantum interference devices (SQUIDs) and their quantum analogues (qubits) as meta-atoms in superconducting microwave metamaterials has become increasingly appealing as the attention of the community shifts towards tunability and parametric effects [1][2][3][4] . In the quantum limit, efforts to build many-qubit systems blur the border between circuit quantum electrodynamics and metamaterials [5][6][7][8] while even the classical case holds a multitude of interesting and yet unexplored possibilities.…”

Wide-band tuneability, nonlinear transmission, and dynamic multistability in SQUID metamaterials

“…The frequency and time in equation (1) are normalized to the corresponding LC SQUID frequency ω 0 = 1/ √ LC and its inverse ω where Ω is the driving frequency, φ dc is the flux bias, and φ ac is the amplitude of the ac field. The current, i n,m , flowing in the (n, m) SQUID, normalized to the critical current of the junction, I c , is given by…”

“…Superconducting metamaterials [1], a particular class of artificial media that rely on the extraordinary properties of superconductors at sufficiently low temperatures, have been recently attracted great attention (see e.g., reference [2]). Conventional metamaterials, that comprise highly conducting metallic elements [3,4,5], typically exhibit high losses in the frequency range where their unusual and sought properties are manifested.…”

Refractive index in generalized superconductors with Born–Infeld electrodynamics

“…Since then, the study on the negative refraction has attracted intensive interest and a large number of the negative refractive index materials have been introduced [16]. Interestingly, recent studies show that in the radio, microwave and low-terahertz frequency ranges the superconductors can behave as metamaterials and exhibit negative refraction [17]. Using the AdS/CFT correspondence, Gao and Zhang investigated the optical properties in the s-wave superconductors and found that the negative refraction does not appear in these holographic models in the probe limit [18].…”