Search results for "Energy engineering"
showing 10 items of 1099 documents
Characterisation of Cooper pair boxes for quantum computing
2001
We have measured and characterised superconducting single Cooper pair boxes (SCB) using superconducting single electron transistor (SET) fabricated on the same chip as an electrometer. The electrometer is sensitive to the potential changes of the SCB island and thus measures the number of excess Cooper pairs on the island. The boxes were of the Al/AlOx/Al Josephson junction type. The SCB and SET were characterised separately and the box storage performance for Cooper pairs was analysed by observing the changes in the SCB island potential while sweeping the gate voltage.
Macroscopic persistent currents in laser deposited YBa2Cu3O7 films
1989
We have investigated persistent currents in a superconducting YBa2Cu3O7 ring of about 1 cm diameter, which was deposited as c-axis textured film on a SrTiO3 substrate by laser ablation. The currents were registered, via their magnetic field distribution, with a small vibrating pick-up coil. At 77 K persistent currents with negligible decay over 103 s have been observed below a critical current density jc=0.9×105 A/cm2, both for a field-cooled and a zero-field-cooled sample. This demonstrates that it is possible to fabricate dissipationless devices of such films on a relatively large scale.
A facile semi-open method for synthesis of non-centrosymmetric superconducting Li2(Pd,Pt)3B bulks and thin films
2010
Abstract Non-centrosymmetric superconductor Li 2 (Pd 1− x Pt x ) 3 B, x = 0–1 was synthesized from mixtures of the elements. A simple semi-open method is proposed using endings-pressed stainless steel tubes placed in a high-vacuum furnace. Heating regime employed a short-time overheating at 900 °C and a slow cooling step between T s and 550 °C within 3 h. To adequately compensate Li-losses and attain maximum critical temperature, the optimum T s and starting Li-content were found to change from 720 to 740 °C and from Li 2.4 to Li 2.6 , respectively, when x was changing from 0 to 1. It was shown that placing Li separately in the tube also produces superconducting samples, Li being supplied …
(Bi,Pb)2Sr2Ca2Cu3O10+δ superconductor composites: Ceramics vs. fibers
1991
Abstract Well characterized (Bi, Pb) 2 Sr 2 Ca 2 Cu 3 O 10+δ superconductor powder has been used to prepare superconductor-glass, -metal and -alloy composites through solid state reaction method. A recently developed Laser Floating Zone (LFZ) apparatus has been used to transform the ceramic precursors into oriented fibers. The diamagnetic properties have been studied by a.c. susceptibility. The microstructure of fibers has been studied by SEM and compared with that of the original ceramic precursors. XRD has been used to study phase composition on representative composite samples and fibers. The results indicate some potential for the 2223-Ag composite, which displays improved diamagnetic p…
Resistivity and irreversibility line of (Hg0.9Re0.1)Ba2CaCu2O6+δ HTS thin films
2003
Abstract High-quality epitaxial (Hg 0.9 Re 0.1 )Ba 2 CaCu 2 O 6+ δ HTS thin films were successfully prepared by pulsed laser deposition (PLD) of Hg-free precursor material on (1 0 0)-oriented SrTiO 3 substrates with subsequent Hg vapour annealing. (Hg 0.9 Re 0.1 )Ba 2 CaCu 2 O 6+ δ HTS thin films exhibit sharp superconducting transitions at T c ≈122 K. The electrical resistance for c -axis oriented HgRe-1212 films has been studied as a function of temperature and dc magnetic fields up to 10 T parallel to the crystallographic c -axis. The irreversibility line for the HgRe-1212 has been deduced from the data and investigated as a function of reduced temperature T / T c . The result of the irr…
Microwave electrodynamics of the antiferromagnetic superconductor GdBa2Cu3O7−δ
1999
The temperature dependence of the microwave surface impedance and conductivity are used to study the pairing symmetry and properties of cuprate superconductors. However, the superconducting properties can be hidden by the effects of paramagnetism and antiferromagnetic long-range order in the cuprates. To address this issue we have investigated the microwave electrodynamics of GdBa_2Cu_3O_{7-\delta}, a rare-earth cuprate superconductor which shows long-range ordered antiferromagnetism below T_N=2.2 K, the Neel temperature of the Gd ion subsystem. We measured the temperature dependence of the surface resistance and surface reactance of c-axis oriented epitaxial thin films at 10.4, 14.7 and 17…
Tunneling spectroscopy of giant vorticity states in superconducting micro- and nanorings at ultra-low temperatures
2008
Abstract When a superconducting contour is exposed to a magnetic field screening currents are induced. At temperatures well below the critical temperature Tc periodicity of the persistent currents can significantly exceed the superconducting flux quantum h / 2 e due to formation of metastable energy states with high quantum winding numbers (vorticity). We have studied the effect in normal metal-insulator-superconductor (NIS) and SIS’IS tunnel structures with the superconducting (S or S′) electrode in a shape of a loop. The tunnel current oscillates due to the modulation of the superconducting density of states by the persistent currents reaching the sub-critical values. In the limit of loop…
Normal and mixed state Hall effect in (Hg0.9Re0.1)Ba2CaCu2O6+δ fully textured HTSC thin films
2004
Abstract Temperature and magnetic field dependence of the Hall effect in the normal and mixed state of fully textured (Hg0.9Re0.1)Ba2CaCu2O6+δ (HgRe-1212) HTSC thin films prepared by laser ablation deposition have been studied. The longitudinal resistivity ρxx and Hall resistivity ρyx of HgRe-1212 superconductor thin films were measured for a wide range of magnetic fields from 125 mT to 12 T with the field perpendicular to the ab plane and the current in the ab plane. A sign change of the Hall resistivity is observed in fields below 3 T in the region close to the superconducting onset temperature. The temperature dependencies ρxx ∝ T and ρyx ∝ 1/T have been observed for HgRe-1212 thin films…
Probing the superconducting state of UPd2Al3 thin films by tunneling spectroscopy
1997
Abstract Giaever-type planar cross junctions of thin films of the heavy fermion superconductor UPd2Al3 and counter-electrodes of Au, Ag and Al were prepared. Tunneling barriers consisting of the native oxide layer of UPd2Al3 and artificial barriers of AlOx and UOx were investigated. The junctions without artificial barrier show a lack of reproducebility. On some junctions a BCS-like tunneling conductivity with a ratio of 2Δ 0 /k B T c ⋍ 3.8 was observed. Using oxidized Al deposited at room temperature as a barrier no substantial increase of the junction resistance occured. With Uraniumoxide a much higher resistance was obtained, but an association of the bias dependent junction conductivity…
Vortex-system ordering during magnetisation measurements in YBa2Cu3O7−δ films at low temperatures
2007
Abstract Zero-field-cooling dc magnetisation relaxation measurements performed on optimally doped epitaxial YBa 2 Cu 3 O 7− δ films with the external magnetic field H oriented parallel to the c -axis reveal the ordering of the creeping vortex-system in the low temperature T domain, due to the macroscopic currents induced in the sample. This dynamic ordering manifests itself through the appearance of a maximum in the T variation of the normalised vortex-creep activation energy. The location of this maximum in the H – T plane describes a well-defined current induced order–disorder line. Our results suggest the absence of a static elastic vortex glass in disordered high-temperature superconduc…