A one-dimensional tunable magnetic metamaterial

Abstract

Abstract:We present experimental data on a one-dimensional superconducting metamaterial that is tunable over a broad frequency band. The basic building block of this magnetic thin-film medium is a single-junction (rf-) superconducting quantum interference device (SQUID). Due to the nonlinear inductance of such an element, its resonance frequency is tunable in situ by applying a dc magnetic field. We demonstrate that this results in tunable effective parameters of our metamaterial consisting of 54 rf-SQUIDs. In order to obtain the effective magnetic permeability µ r,eff from the measured data, we employ a technique that uses only the complex transmission coefficient S 21 .

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

“…Tuneability of an rf SQUID can be achieved either with the amplitude of the ac field, φ ac , or with the flux bias, φ dc , which generate the flux threading its loop [35]. The resonance shift due to a dc flux bias has been actually observed in low−T c , single rf SQUIDs in the linear regime [18], as well as in 1D SQUID metamaterials [19,32,56]. Assuming isotropic coupling, i.e., λ x = λ y = λ, the maximum and minimum values of the linear frequency band are then obtained by substituting κ = (κ x , κ y ) = (0, 0) and (π, π), respectively, into equation (5).…”

“…Superconductors, on the other hand, are intrinsically nonlinear materials, due to the extreme sensitivity of the superconducting state in external stimuli [7,8], which moreover exhibit significantly reduced Ohmic losses. They thus provide unique opportunities to the researchers in the field for the fabrication of superconducting metamaterials with highly controllable effective electromagnetic properties including wideband tuneability [9,10,11,12,13,14,15,16,17,18,19,20].…”

“…The replacement of metallic SRRs with rf SQUIDs, which have no direct electrical conduct but instead they are coupled magnetically through their mutual inductances, has been suggested theoretically a few years ago [30,31]. Such SQUID metamaterials have been recently realized in the lab [18,19,32,24,25], that exhibit strong nonlinearities and wide-band tuneability with unusual magnetic properties due to macroscopic quantum effects. Nonlinearity and discreteness in SQUID metamaterials, along with low Ohmic losses (at least at microwave frequencies) may also lead in the generation of discrete breathers [33,34,35], i.e., time-periodic and spatially localized modes that change locally the magnetic response.…”

“…Their operation frequency spans a huge range, from zero [51,52,53,54] to microwaves [55,18,56,19,32] and to Terahertz [11,12,37,57,38,39,40,15,58,59,41,42] and visible [45] frequencies. Moreover, researchers rely on particular superconducting devices to access the trully quantum metamaterial regime [30,60,61,62,63].…”

Giant nonlinearity in a superconducting sub-terahertz metamaterial

“…Before proceeding, we will briefly overview the properties that make the superconducting metamaterials particularly well-suited for operation at frequencies up to and including terahertz. 17 The superconducting metamaterials offer low Joule losses, sub-nanosecond nonlinear response, [18][19][20] access to quantum-mechanical phenomena through the inclusion of Josephson junctions, [21][22][23] and sensitivity to light, 24 magnetic field, and temperature. 7,25,26 The nonlinear response of the superconductors at terahertz/sub-THz frequencies occurs via two mechanisms.…”