1,721,073 research outputs found
Radiation-harvesting sub-THz bolometer based on resonant superconducting metamaterial
No full textWe demonstrate a sub-THz superconducting metamaterial bolometer with selective response that exploits inter-molecular electromagnetic interactions in the electrically interconnected network of superconducting resonators and superconducting phase-transition edge sensitivity of the electrical interconnect
Radiation-harvesting resonant superconducting sub-THz metamaterial bolometer
No full textWe demonstrate a sub-THz superconducting metamaterial bolometer with selective response that exploits intermolecular electromagnetic interactions in the electrically interconnected network of superconducting resonators, and superconducting phase-transition edge sensitivity of the electrical interconnect
A comparative study of thallium and bismuth 2223 superconducting tapes using a SQUID picovoltmeter
No full textModelling magnetic exchange springs in 1D, 2D, and 3D
No full text1D models of magnetic multilayers, with alternating hard and soft layers, are extended to 2D and 3D, and presented within a common framework of nearest neighbour interactions. Using 2D calculations, it is shown that the properties of magnetic exchange springs can be changed significantly by patterning the hard pinning layers. But, in certain cases the bending field BB is not significantly altered, even when half the pinning layer is removed. 3D calculations are used to probe the effects of defects on the properties of magnetic exchange springs, using epitaxial DyFe2/YFe2 superlattices as an example. It is shown that point defects such as Fe vacancies have little effect on the bending field transition. This is in marked contrast to the 1D model, where an Fe vacancy cuts the magnetic exchange spring into two. Finally, it is demonstrated that significant changes in the properties of magnetic exchange springs can be engineered, by placing rare-earth ions in the centre of the soft YFe2 springs. A new phenomenon, exchange spring collapse, is predicte
Radiation-harvesting resonant superconducting sub-THz metamaterial bolometer
No full textWe demonstrate a frequency-selective energy-harvesting sub-THz superconducting bolometer. The bolometer, a two-dimensional array of connected metamaterial resonators, exploits the collective mode of the metamaterial excitation to collect incident radiation and channel it into the bolometer hot-spot located on the connecting wire. The sharp dependence of the resistivity of the wire on the temperature at the hot-spot is utilized for radiation detection. Our approach allows combination of the radiation harvesting, spectral selectivity and detection functions in a single planar metamaterial structure
Electro-optical modulation of sub-terahertz radiation with superconducting metamaterial
No full textWe present the first demonstration of electro-optical modulator of sub-terahertz radiation where intensity and phase modulation is achieved by running current through a superconducting network of niobium meta-molecules supporting a high-Q resonance
Monte Carlo simulation of layered high temperature superconductors
No full textWe present results from Monte Carlo simulations of the vortex state in layered high temperature superconductors. We use a set of potentials derived from the Lawrence-Doniach free-energy functional which incorporates (i) intra-layer coupling (ii) inter-layer Josephson and electromagnetic interactions. We have employed a novel technique for performing an in-plane infinite lattice summation for the intra-layer interactions. This provides a minimum 50,000 times faster speed-up in the simulations over previous naïve methods which add periodic images in shells of increasing radius. We present results of the numerical B-T phase diagram in the pure system and obtain good agreement with available experimental/theoretical results
Electro-optical modulation of sub-terahertz radiation in a superconducting metamaterial
No full textWe report the first demonstration of electro-optical modulation of millimetre-wave radiation using a superconductor metamaterial. High-contrast intensity and phase modulation is achieved via the distraction of the superconducting state by current running through the metal network of niobium metamaterial. The asymmetrically split-ring niobium metamaterial at temperatures below Tc supports a Fano-type mode of excitation associated with high-quality resonances (Q~130) in its transmission and absorption spectra. Current up to 700mA running through the niobium network of metamolecules is sufficient to induce a phase transition in the superconductor which is accompanied by an increase of the Joule losses and a degradation of the Fano resonance. A nearly 100% modulation of the metamaterial's transmission and reflection at the resonance frequency of about ~100GHz has been demonstrated. We also demonstrated a 500kHz amplitude modulation of the sub-terahertz carrier signal and believe that the modulation rate can be improved further
Lock-in oscillations in magnetic hysteresis curves of YBa2Cu3O7-x single crystals
No full textWe report the first direct experimental evidence of intrinsic pinning in hysteresis loops of untwinned YBa2Cu3O7-x single crystals, for magnetic fields perpendicular to the c axis. We have observed oscillations in the M-H loops that are well explained when one considers the layered structure of this compound. The oscillations are found to be periodic in H-1/2a and are induced by a succession of transitions between states for which the vortex lattice is commensurate with the crystal lattice periodicity in the direction perpendicular to the CuO2 planes. The following anisotropy parameters were extracted from the experimental results: Gamma cb=(mc/mb)1/2=6.3, Gamma ca=(mc/ma)1/2=5.6, and Gamma ab=(ma/mb)1/2=1.13
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