A.R. Buckingham

Superconducting plasmonics and extraordinary transmission

Negative dielectric constant and dominant kinetic resistance make superconductors intriguing plasmonic media. Here we report on the effect of extraordinary transmission through an array of sub-wavelength holes in a perforated film of high-temperature YBCO superconductor.

Flux Exclusion Superconducting Quantum Metamaterial: Towards Quantum-level Switching

Nonlinear and switchable metamaterials achieved by artificial structuring on the subwavelength scale have become a central topic in photonics research. Switching with only a few quanta of excitation per metamolecule, metamaterials elementary building block, is the ultimate goal, achieving which will open new opportunities for energy efficient signal handling and quantum information processing. Recently, arrays of Josephson junction devices have been proposed as a possible solution. However, they require extremely high levels of nanofabrication. Here we introduce a new quantum superconducting metamaterial which exploits the magnetic flux quantization for switching. It does not contain Josephson junctions, making it simple to fabricate and scale into large arrays. The metamaterial was manufactured from a high-temperature superconductor and characterized in the low intensity regime, providing the first observation of the quantum phenomenon of flux exclusion affecting the far-field electromagnetic properties of the metamaterial.

Engineering irreversibility of exchange springs in antiferromagnetic DyFe2/YFe2 superlattices

Irreversible exchange springs are experimentally observed in an antiferromagnetic (DyFe2 40 A/YFe2 80 A/DyFe2 8 A/YFe2 80 A) × 20 superlattice. Two irreversible exchange springs can be observed at 80 K with field along the [00] crystal direction. OOMMF micromagnetic simulation is employed to understand the underlying physics. It is confirmed that the induced anisotropy in the soft phase, by the 8 A thick DyFe2 layer, is mainly responsible for the observed irreversibility, which corresponds to switching between energy minima of the thin hard inclusion in the soft phase. The qualitative agreement between experiment and simulation is satisfactory. This demonstrates the feasibility to control the irreversibility of exchange spring winding and unwinding processes in antiferromagnetically coupled superlattices. This additional degree of freedom in the demagnetization process of the soft layers of exchange coupled superlattices can be utilized to reduce the switching field of a hybrid magnet through spin-wave assisted magnetization reversal.

Flux exclusion quantum superconducting metamaterial

The new type of metamaterial exploits magnetic flux quantization as a source of its nonlinear response but does not require Josephson junctions. We fabricated metamaterial from a high-Tc superconductor and report its electromagnetic characterization.