Yttrium Barium Copper Oxide Superconductor Research Articles

Coupling Sub-nanoliter BDPA Organic Radical Spin Ensembles with YBCO Inverse Anapole Resonators

We report the development and test of planar microwave Inverse Anapole Resonators (IARs) made of superconducting Yttrium Barium Copper Oxide (YBCO) for electron spin resonance spectroscopy on small samples. We first characterize our resonators in zero field and then by carrying out transmission spectroscopy on a diluted $$\alpha ,\gamma $$ -bisdiphenylene- $$\beta $$ -phenylally (BDPA) organic radical spin ensemble in an applied magnetic field. These IARs allow us to carry out electron spin resonance spectroscopy both in continuous-wave and pulsed-wave mode, and to estimate the spin memory time of BDPA. The comparison with the results obtained for the same sample on typical linear coplanar resonators shows an improvement by $$\approx 2\text { - up to}\,3$$ – orders of magnitude in spin sensitivity, with effective sensing volumes below 1 nanoliter. The best sensitivity we achieved is $$S\approx \,10^{7}\,\text {spin}/\sqrt{\mathrm{Hz}}$$ in the pulsed-wave regime. These results compare well with similar experiments reported in the literature.

Dual Frequency Mixing Products and Terahertz Hilbert-Transform Spectroscopy With Josephson Cantilevers in a THz Microscope

Josephson cantilevers, based on high-temperature superconducting yttrium barium copper oxide Josephson junctions, can be employed for the measurement of frequency and power of microwave and terahertz radiation. Each Josephson cantilever carries at least one Josephson junction with a dedicated antenna structure for better coupling. In the THz microscope, such cantilevers are employed for spatially resolved measurements of radiation distributions over either active emitting or passive samples that are irradiated by an external terahertz source. The power distribution can be reconstructed from Shapiro steps in the current-voltage characteristic of the cantilever's Josephson junction by methods including Hilbert spectroscopy. We show that simulations with simultaneous excitation with more than a single frequency result in the appearance of Shapiro steps at sum and difference frequencies. The amplitudes of these steps approximately follow Bessel functions, as with the Shapiro steps from single frequency excitation. This is confirmed by a setup in the THz microscope, where the Josephson cantilever is simultaneously subjected to 40 GHz radiation of variable power and 693 or 762 GHz radiation from a far-infrared laser system. Josephson mixing spectra show peaks at sum and difference frequencies following Bessel curves with increasing power, as it was predicted for the according Shapiro steps. These products should be avoided for a reconstruction of the original signals by Hilbert spectroscopy.

THz Radiation Measurement with HTSC Josephson Junction Detector Matched to Planar Antenna

Superconducting Josephson junctions have major advantages as detectors of millimeter wave radiation. Frequency of the radiation can be easily derived from the Shapiro steps of the current-voltage characteristics. However, system performance is highly sensitive to impedance mismatch between the antenna and the junction; therefore, optimization is essential. We analyzed and implemented an improved antenna structure, in which the junction is displaced from the antenna center and placed between the ends of two matching strips. Based on theoretical analysis and advanced electromagnetic simulations, we optimized strip dimensions, which affect both the detection magnitude and the frequency of the reflection coefficient dip. Accordingly, two Au bow-tie antennas with different matching strip widths were fabricated. Superconducting Yttrium Barium Copper Oxide (YBCO) thin films were deposited exactly at the bicrystal substrate misorientation points, forming Josephson junctions at the ends of two matching strips. We found a very high correlation between the simulations and the response to Radio Frequency (RF) radiation in the range of 145–165 GHz. Experimental results agree extremely well with the design, showing best performance of both antennas around the frequency for which impedance matching was derived.

A Study of a Narrow-Band Receiving System of Cold-Electron Bolometers for the 220 and 240 GHz Channels using an Oscillator Based on the High-Temperature YBCO Superconductor

We present the results of theoretical and experimental studies of the resonant properties of a single cell of a receiving system based on cold-electron bolometers (CEBs) with a double-slot antenna and curved coplanar lines, which is intended for receiving a signal in the range 220–240 GHz with a bandwidth of 5%. The resonant properties of a CEB located on the cryostat plate with a temperature of 0.3 K, are measured using an oscillator based on high-temperature superconductor (HTS) of yttrium barium copper oxide (YBCO), placed inside the same cryostat on a plate with a temperature of 4 K, which allows one to obtain smooth amplitude-frequency characteristics.

Microwave dual-mode resonators for coherent spin-photon coupling

We implement superconducting Yttrium barium copper oxide planar resonators with two fundamental modes for circuit quantum electrodynamics experiments. We first demonstrate good tunability in the resonant microwave frequencies and in their interplay, as emerges from the dependence of the transmission spectra on the device geometry. We then investigate the magnetic coupling of the resonant modes with bulk samples of 2,2-diphenyl-1-picrylhydrazyl organic radical spins. The transmission spectroscopy performed at low temperature shows that the coherent spin-photon coupling regime with the spin ensembles can be achieved by each of the resonator modes. The analysis of the results within the framework of the input-output formalism and by means of entropic measures demonstrates coherent mixing of the degrees of freedom corresponding to two remote spin ensembles and, with a suitable choice of the geometry, the approaching of a regime with spin-induced mixing of the two photon modes.

Levitation force of melt-textured YBCO superconductors under non-quasi-static situation

The superconducting levitation force of a simple superconductor-magnet system under non-quasi-static situation is investigated experimentally. Two yttrium barium copper oxide (YBCO) samples with different performances are chosen from two small batches of samples prepared by the top-seeded melt-textured growth process. The residual carbon content of the precursor powders of the two batches is different due to different heat treatment processes. During the experimental process for measuring the levitation force, the value of the relative speed between the YBCO sample and the permanent magnet is higher than that in conventional studies. The variation characteristics of the superconducting levitation force are analyzed and a crossing phenomenon in the force–displacement hysteresis curves is observed. The results indicate that the superconducting levitation force is different due to the different residual carbon contents. As residual carbon contents reduce, the crossing phenomenon is more obvious accordingly.

Accessing the High‐Q Dark Plasmonic Fano Resonances in Superconductor Metasurfaces

Superconducting metamaterials at terahertz frequencies has provided a platform for designing switchable plasmonic metamaterial devices. However, since metals at terahertz frequencies are excellent conductors, the superior role of superconductors in designing low‐loss, high quality factor metamaterials remains unclear. In this work, a low asymmetry Fano resonant split‐ring‐resonator is considered in which a regime of extremely low radiative loss is identified where the high temperature yttrium barium copper oxide superconductor meta‐atom supports a sharp high quality factor Fano resonance while an identical metallic resonator does not show the resonance behavior. The radiative and the nonradiative losses are comparable in low asymmetry Fano resonant meta‐atoms. The observation of high quality factor Fano resonance behavior clearly establishes the utility of superconductors over metals in designing lower loss plasmonic metamaterials at terahertz frequencies that may have multifunctional applications in areas that require strong light–matter interactions.

Dual ion beam assisted magnetron deposition of biaxially textured YSZ and YBCO/YSZ thin films

Abstract Biaxially textured yttria stabilized zirconia (YSZ) thin films were deposited on polished hastelloy and silicon substrates using ion beam assisted deposition (IBAD). The IBAD apparatus includes a planar magnetron fitted with a crystalline YSZ target to provide the film-forming species, and two Kaufman-type ion beam sources which provide Ar+ ions for bombarding the film during growth. The two ion beam sources were mounted symmetrically at 55° angles to the substrate plane normal, making 110° angle between them. Textured YSZ films were deposited under three different IBAD conditions: (a) films were bombarded by a single ion beam source (SIBAD), (b) films were bombarded by a single ion beam source for a time alternating from the two symmetric directions (AIBAD), and (c) by dual ion beam assisted deposition (DIBAD) where the film was bombarded simultaneously from the two symmetric directions. The X-ray φ-scan results indicate that DIBAD followed by epitaxial growth of YSZ produced the highest degree of biaxial texture in YSZ films. Superconducting yttrium barium copper oxide (YBCO) films deposited on highly textured DIBAD YSZ films had φ-scan full width at half maximum of 7.1° and 5.5° for hastelloy and silicon substrates, respectively.

The Effect of Dy Doping on the Magnetic Behavior of YBCO Superconductors

The effect of dysprosium (Dy) doping on yttrium barium copper oxide (YBCO) prepared by conventional solid-state reaction method has been investigated by means of XRD, AC susceptibility, and DC magnetization measurements. AC susceptibility measurements for sintered YBCO pellets have been performed as a function of temperatures at constant frequency and AC field amplitude in the absence of a DC bias field. DC magnetization measurements were done at 5, 20, and 77 K upon zero field cooling (ZFC) process. The magnetization measurements showed a paramagnetic behavior existing at high magnetic fields. The magnetic field dependence of critical current density of the samples has been estimated from DC magnetization data. The partial Dy substitution for Y on YBCO superconductors improves the bulk critical current density at high magnetic fields and at high-temperature regions (higher than 20 K).

Application of computational intelligence technique for estimating superconducting transition temperature of YBCO superconductors

Yttrium barium copper oxide (YBCO) is a high temperature superconductor with excellent potential for long distance power transmission applications as well as other applications involving generation of high magnetic field such as magnetic resonance imaging machines in hospitals. Among the uniqueness of this material is its perpetual current carrying ability without loss of energy. Practical applications of YBCO superconductor depend greatly on the value of the superconducting transition temperature (TC) attained by YBCO superconductor upon doping with other external materials. The number of holes (i.e. doping) present in an atom of copper in CuO2 planes of YBCO superconductor controls its TC. Movement of the apical oxygen along CuO2 planes due to doping gives insight to the way of determining the effect of doping on TC using the bound related quantity (lattice parameter) that is easily measurable with reasonable high precision. This work employs excellent predictive and generalization ability of computational intelligence technique via support vector regression (SVR) to develop a computational intelligence-based model (CIM) that estimates the TC of thirty-one different YBCO superconductors using lattice parameters as the descriptors. The estimated superconducting transition temperatures agree with the experimental values with high degree of accuracy. The developed CIM allows quick and accurate estimation of TC of any fabricated YBCO superconductor without the need for any sophisticated equipment.

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ChemInform Abstract: Probing the Electronic Structure of Yttrium Barium Copper Oxide Superconductors by Copper, Oxygen, and Barium NQR and NMR

ChemInform Abstract: Probing the Electronic Structure of Yttrium Barium Copper Oxide Superconductors by Copper, Oxygen, and Barium NQR and NMR

Terahertz superconductor metamaterial

We characterize the behavior of split ring resonators made up of high transition temperature yttrium barium copper oxide superconductor using terahertz time-domain spectroscopy measurements and numerical simulations. The superconductor metamaterial is found to show a remarkable change in the transmission spectra at the fundamental inductive-capacitive resonance as the temperature dips below the critical transition temperature. This resonance switching effect is normally absent in traditional metamaterials made up of regular metals. The temperature-dependent resonance behavior of the superconducting metamaterial would lead to development of low loss terahertz switches at cryogenic temperatures.

Particle size dependence of the superconductivity and ferromagnetism in YBCO nanoparticles

Magnetic properties of superconducting yttrium barium copper oxide (YBa2Cu3O7-δ) nanoparticles (31–43 nm) prepared by a chemical route have been studied. These nanoparticles have been found to clearly exhibit ferromagnetism at room temperature while superconducting transition is observed at lower temperatures. The low temperature hysteresis loops show evidence suggesting the presence of a large paramagnetic contribution in addition to the superconducting contributions from the particles. Bulk YBCO obtained by pelletizing and heating the same nanoparticles at a high temperature, displays the usual superconducting characteristics and gives no trace of ferromagnetism down to 10 K. The superconducting transition temperature of the nanoparticles is lower than for the bulk YBCO and there is a trend of decreasing T c with smaller size of the particles. In contrast the ferromagnetic moment increases with decreasing particle size. The development of ferromagnetism is attributed to the presence of surface oxygen vacancies that lead to electron redistribution on the different ions at the surface. The simultaneous decrease of superconducting T c and the increase of ferromagnetism with decreasing size considered as being reflective of the increased role of finite size and surface defects that weaken the superconductivity and enhance the ferromagnetism. Possible coexistence of surface ferromagnetism and bulk superconductivity at lower temperatures is discussed.

Superconducting Yttrium Barium Copper Oxide Thin Films Growing on the Strained Substrates

The article is devoted to formation of superconducting thin films on the single-crystal substrate where areas with different values of the critical current density are, that is needed for fabrication of superconducting devices. The method is based on an establishment of elastic mechanical stresses on the substrate crystal under the nanosecond focused pulsed laser irradiation. On the irradiated substrate the superconducting thin film having auxiliary elastic stresses not till the area is over the irradiated section of the substrate is grown. At the same time the critical film current density is suppressed for required values are used to fabricate Josephson junctions. Observations for a long time demonstrate superconducting transport film properties are not varied significantly during the maintenance.

Observations of a hysteresis loss valley in yttrium barium copper oxide superconductors

We present measurements of the ac susceptibility of sintered yttrium barium copper oxide pellets prepared by a melt processed solid state reaction method, with different amounts of ZnO added. The measurements were performed versus temperature T for several different ac magnetic field amplitudes Hac in the presence of static bias magnetic fields Hb directed along Hac. For all our samples, for each choice of Hac, the imaginary part of the ac susceptibility versus T traces a peak, denoted by χ″max, centered at a temperature denoted by Tmax.We also find that plots of the values of χ″max vs Hac and of χ″max vs Tmax generate curves that display a valley. Calculations of hysteresis losses, exploiting a critical-state model where the critical current density jc=α(T)∕Bn, reproduce the experimental data quite well.

Effect of Temperature on Impedance Behavior of Insulation Layer in a HTS MEMS Switch for RF Applications

We have successfully developed High Temperature Superconducting (HTS) MicroElectroMechanical (MEM) switches for RF applications. A typical switch is composed of a superconducting Yttrium Barium Copper Oxide (YBa/sub 2/Cu/sub 3/O/sub 7/) coplanar waveguide structure with a gold bridge membrane suspended above an area of the center conductor covered with Barium Titinate (BaTiO/sub 3/) ferroelectric. A control voltage applied between the membrane and transmission line causes the membrane to collapse on top of the dielectric layer by electrostatically induced force; this in turn allows the RF signal to capacitively shunt to ground. Initial testing of switches showed very promising RF behavior with insertion losses less than 0.1dB with 30 dB isolation at 3 GHz. These switches rely on the "ON/OFF" impedance ratio to achieve switching; this is determined by the dielectric constant of the BaTiO/sub 3/ ferroelectric. These switches will be operated at cryogenic temperatures; we have investigated the impedance behavior vs. temperature of the HTS/ferroelectric/metal heterostructure to better understand the behavior of the insulating layer at cryogenic temperatures.

Pulsed-Laser Deposition of Biaxially Textured YSZ/CeO2 Films on Electrodeposited Ir/Ni-W Tapes for YBCO Superconductors

AbstractIridium film is a potential candidate as a buffer layer for yttrium barium copper oxide (YBCO) coated conductors. Pulsed laser deposition (PLD) of biaxially textured CeO2/yttrium stabilized zirconium oxide (YSZ) layers on electrodeposited Ir/Ni-W is reported. Biaxial texturing is obtained by deposition of a YSZ seed layer at 800°C in 10-6 Torr vacuum. X-ray diffraction (XRD) studies of Θ-2Θ and pole figure confirmed in-plane out-of-plane biaxial texturing with Δφ = 6.5° and Δω = 8°. Atomic force microscopy (AFM) revealed a surface with roughness of about 3 nm.

Double-sided sputtering deposition of YBa/sub 2/Cu/sub 3/O/sub 7-δ/ thin films on 2" LaAlO/sub 3/ wafers for microwave applications

Superconducting yttrium barium copper oxide films were prepared on 2" lanthanum aluminate substrates by sputtering from a cylindrical and stoichiometric target. The deposition parameters were studied in order to obtain in a reproducible manner a sufficiently low value of the surface resistance for microwave applications. The typical value at 10 GHz and 77 K was 0.35 m/spl Omega/ down to 0.2 m/spl Omega/. The purpose of this work was the subsequent deposition of YBa/sub 2/Cu/sub 3/O/sub 7-z/ on the LaAlO/sub 3/ backside without degradation of the first deposit. The fabrication of the subsequent deposit was made with the same deposition parameters as the first film after turning over the substrate at room temperature. The physical and structural properties of both side deposits were analyzed (RBS, ion channeling, MEB, XRD, Rs and electrical resistivity). Although the first film underwent a second thermal process during the subsequent deposition, the surface resistance value was not degraded. This unexpected result is discussed in the frame of the mechanism of oxygenation in YBa/sub 2/Cu/sub 3/O/sub 7-x/ film by changing the conditions of sample cooling. An example of a microwave filter using this double-sided structure is presented.

Oxide epitaxial lift-off of superconducting thin film devices

Oxide epitaxial lift-off (OELO) has been successfully accomplished for thin single layer films of strontium titanate and multilayer films of strontium titanate and superconducting yttrium barium copper oxide (YBCO). The technique employs a YBCO release layer to separate the films from the growth substrate. The critical development was the use of a polymer support layer which retains sufficient compliance after curing to permit stress relaxation of the oxide film in such a way as to prevent cracking. Multilayer lift-off had the additional necessity of encapsulating the YBCO device layer. This was accomplished by alternately depositing layers of strontium titanate and YBCO. Layer thicknesses were optimized to compensate for the resulting through-thickness stress gradient which developed due to thermal expansion differences.