Study of High-Temperature Superconductor Diplexers for Satellite Communications

The high-temperature superconductor （HTSC） resonator and diplexer are simulated by full-wave tools. A newly developed miniature HTSC diplexer is designed and fabricated on double sided YBa2Cu3O7 （YBCO） film （YBCO/LaAlO3/YBCO）, the thickness of which is 400 nm for YBCO and 0.5 mm for the LaAlO3. The measured results show a good agreement with the simulation. The volume and mass of the diplexers are greatly reduced by miniaturized configuration.

Angular dependence of vertical force and torque when magnetic dipole moves vertically above flat high-temperature superconductor

The interaction between a permanent magnet(PM)assumed as a magnetic dipole and a flat high-temperature superconductor(HTS)is calculated by the advanced frozen-image model.When the dipole vertically moves above the semiinfinite HTS,the general analytical expression of vertical force and that of torque are obtained for an arbitrary angle between the magnetization direction of the PM and the c axis of the HTS.The variations of the force and torque are analyzed for angle and vertical movements in both zero-field cooling(ZFC)condition and field cooling(FC)condition.It is found that the maximum vertical repulsive or attractive force has the positive or negative cosine relation with the angle.However,the maximum torque has the positive or negative sine relation.From the viewpoint of the rotational equilibrium,the orientation of the magnetic dipole with zero angle is deemed to be an unstable equilibrium point in ZFC,but the same orientation is considered as a stable equilibrium point in FC.In addition,both of the variation cycles of the maximum force and torque with the angle areπ.

Lateral magnetic stiffness under different parameters in a high-temperature superconductor levitation system

Magnetic stiffness determines the stability of a high-temperature superconductor(HTS)magnetic levitation system.The quantitative properties of the physical and geometrical parameters that affect the stiffness of HTS levitation systems should be identified for improving the stiffness by some effective methods.The magnetic stiffness is directly related to the first-order derivative of the magnetic force with respect to the corresponding displacement,which indicates that the effects of the parameters on the stiffness should be different from the relationships between the forces and the same parameters.In this paper,we study the influences of some physical and geometrical parameters,including the strength of the external magnetic field(B0)produced by a rectangular permanent magnet(PM),critical current density(Jc),the PM-to-HTS area ratio(α),and thickness ratio(β),on the lateral stiffness by using a numerical approach under zero-field cooling(ZFC)and field cooling(FC)conditions.In the first and second passes of the PM,the lateral stiffness at most of lateral positions essentially increases with B0 increasing and decreases withβincreasing in ZFC and FC.The largest lateral stiffness at every lateral position is almost produced by the minimum value of Jc,which is obviously different from the lateral force–Jc relation.Theα-dependent lateral stiffness changes with some parameters,which include the cooling conditions of the bulk HTS,lateral displacement,and movement history of the PM.These findings can provide some suggestions for improving the lateral stiffness of the HTS levitation system.

Comparative Study of 10-MW High-Temperature Superconductor Wind Generator with Overlapped Field Coil Arrangement

The electromagnetic characteristics and iron loss of a high-temperature superconductor wind generator(HWG)equipped with an overlapped field coil arrangement(OFCA)are studied by comparing with the one equipped with the conventional field coil arrangement(CFCA).Through a quantitative analysis,it was found that HWG with OFCA exhibits better electromagnetic characteristics than HWG with CFCA and can reduce the iron loss by eliminating the magnetic flux sag caused by the adjacent field coil sides with the same current flow direction.In addition,the OFCA topology can further reduce the volume of the wind generator.

Magnetic levitation performance of high-temperature superconductor over three magnetic hills of permanent magnet guideway with iron shims of different thicknesses

Superconducting magnetic levitation performance, including levitation force and guidance force, is important for the application of high-temperature super- conducting maglev. Both of them are not only affected by different arrays of superconductors and magnets, but also by the thickness of the iron shim between permanent magnets. In order to obtain the best levitation performance, the magnetic field distribution, levitation force, and guidance force of a new type of three magnetic hills of permanent magnet guideway with iron shim of different thicknesses （4, 6, and 8 mm） are discussed in this paper. Simulation analysis and experiment results show that the guideway with iron shim of 8 mm thickness possesses the strongest magnetic field and levitation performance when the suspension gap is larger than 10 mm. However, with the decreasing of suspension gap, the guideway with iron shim of 4 mm thickness possesses the best levitation performance. The phenomena can be attributed to the density distribution of flux and magnetization of iron shim.

Vibration characteristics of a multi-block high-temperature superconducting maglev system

The multi-block high-temperature superconducting （HTS） maglev system has more complicated dynamic characteristics than the single-block HTS maglev system. To study its vibration characteristics, we designed a maglev measurement system. The system responses at the excitation frequencies of 2, 3 and 15 Hz were examined. Results show that the responses under excitation frequencies of 2 and 3 Hz include a 6 Hz component, which means that the maglev system is a critical nonlinear system. Moreover, the 6 Hz component is much stronger than the 2 Hz or 3 Hz components in the response spectra. There is the interaction between excitation and response. Under an excitation frequency of 15 Hz, intensified low-frequency perturbations were observed.

HIGH-TEMPERATURE HEAT CAPACITIES OF THE PHASES IN Y-Ba-Cu-O SYSTEM

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Development of metal-organic deposition-derived second-generation high-temperature superconductor tapes and artificial flux pinning

The second-generation high-temperature superconductor tape(2G-HTS,also known as a coated conductor)based on REBaCuO(REBa_(2)Cu_(3)O_(7-δ))exhibits high current density and potential cost-effective price/performance,compared with conventional superconducting materials.Using commercial 2G-HTS tapes,more than a dozen cable vendors had been manufacturing REBCO cables,such as the latest kilometer-class REBCO cable,which was incorporated into a civil grid on December 2021,as part of the recordbreaking 35-kV-voltage superconductor cable demonstration project in downtown Shanghai.This paper describes the development of HTS-coated conductors,then outlines the various technological routes for their preparation,reviews the artificial flux pinning of coated conductors,and finally summarizes the technological breakthroughs,the latest research advances,and provides an outlook on their application prospects.

Electron-phonon coupling in cuprate and iron-based superconductors revealed by Raman scattering

Electron-phonon coupling （EPC） in cuprate and iron-based superconducting systems, as revealed by Raman scat- tering, is briefly reviewed. We introduce how to extract the coupling information through phonon lineshape. Then we discuss the strength of EPC in different high-temperature superconductor （HTSC） systems and possible factors affecting the strength. A comparative study between Raman phonon theories and experiments allows us to gain insight into some crucial electronic properties, especially superconductivity. Finally, we summarize and compare EPC in the two existing HTSC systems, and discuss what role it may play in the HTSC.

Robustness of s-wave pairing symmetry in iron-based superconductors and its implications for fundamentals of magnetically driven high-temperature superconductivity

Based on the assumption that the superconducting state belongs to a single irreducible representation of lattice symmetry, we propose that the pairing symmetry in all measured iron-based superconductors is generally consistent with the A1g s-wave. Robust s-wave pairing throughout the different families of iron-based superconductors at different doping regions signals two fundamental principles behind high-To superconducting mechanisms： （i） the correspondence principle： the short-range magnetic-exchange interactions and the Fermi surfaces act collaboratively to achieve high-Tc superconductivity and determine pairing symmetries; （ii） the magnetic-selection pairing rule： supercon- ductivity is only induced by the magnetic-exchange couplings from the super-exchange mechanism through cation-anion-cation chemical bonding. These principles explain why unconventional high- Tc superconductivity appears to be such a rare but robust phenomena, with its strict requirements regarding the electronic environment. The results will help us to identify new electronic structures that can support high-Tc superconductivity.

Scaling of ac susceptibility and the nonlinear response function of high-temperature superconductors

The amplitude-dependent ac susceptibility of high-temperature superconductors is shown to obey some empirical scaling relations. We try to analyze this behavior by extending a dc nonlinear response function of mixed state to the ac cases. The derived equations for critical current and ac susceptibility x(T) agree with the scaling relations of experimental data.

高温超导材料与技术的发展及应用

近一个世纪以来,超导理论、超导材料和超导应用技术已经取得了重大的发展,尤其是新近发展的具有很高实用性能的高温超导(HTS)材料与技术,已开始从实验研究走向实际应用阶段．该文简要介绍了高温超导(HTS)材料的发现历史,阐述了HTS带材、块材和薄膜的制备工艺及特性,总结了HTS材料在强电和弱电领域中的应用发展现状．

超导材料在电工领域的应用

超导材料的应用给电工技术带来了质的飞跃。本文介绍了到目前为止已经实用化的几种超导材料及其优缺点,简述了超导材料在电工领域的应用现状。

稀土高温超导体开发应用进展

介绍了稀土超导体的主要类别及ＹＢＣＯ的主要性质。

Critical Scaling of Extended Power Law I - V Isotherms near Vortex Glass Transition

In view of the question about the vortex glass theory of the freezing of disordered vortex matter raised by recent experimental observations, we reinvestigate the critical scaling of high Tc superconductors. It is found that the dc current-voltage characteristic of mixed state superconductors has a general form of extended power law which is based on the Ginzburg-Landau （GL） functional in the similar way as the vortex glass theory. Isotherms simulated from this nonlinear equation fit the experimental I- V data of Strachan et al. [Phys. Rev. Left. 87（2001） 067007]. The puzzling question of the derivative plot for the I - V curves and the controversy surrounding the values of critical exponents are discussed.

实用化高温超导材料研发进展

综述了目前国内外实用化高温超导材料研发的最新进展,系统介绍和总结了Bi-2223、YBCO涂层导体、MgB2线带材和YBCO块材等主要的实用化高温超导材料制备和性能的最新结果。对比了美国、日本和韩国等国家的高温超导材料研发模式,分析了实用化高温超导材料的发展趋势及应用前景。

Influence of Gauge Fluctuation on Electron Pairing Order Parameter and Correlation Functions of a Two-Dimensional System

Based on a two-dimensional electron system with pure gauge field, we demonstrate that the long range order of the electron pairing order parameter can be destroyed by the gauge fluctuation for both s-wave and d-wave symmetric Cooper pair parameters, even if the pure gauge field mediates attractive interaction between the spinup and spin-down electrons, while the signal of the Meissner effect is observable. This model can be used to explain the recent experimental data of the high Tc cuprate superconductors observed.

Study of Pseudogap in Underdoped Cuprate

A mean-field spin-density wave (SDW) analysis of pseudogap in the underdoped cuprates is proposed on the dependence of the energy gap which mimics the pseudogap near (π, 0) point at least. It implies that the pseudogap structure near (π, 0) is not sensitive to the long-range order and will survive leading to the pseudogap phenomenon in the underdoped metallic phase. On the other hand, in the long-range ordering antiferromagnetic region, the mean-field SDW theory holds and the pseudogap structure predicated by the theory should be observable experimentallyv. Then one prediction is that the pseudogap would smoothly extrapolate between itinerant antiferromagnetic phase and underdoped metallic phase.

Electron Correlation in High Temperature Cuprates

Electron correlation plays a key role in high-temperature cuprate superconductors. Material-parameter dependence of cuprates is important to clarify the mechanism of high temperature superconductivity. In this study, we examine the ground state of the three-band Hubbard model (d-p model) that explicitly includes oxygen p orbitals. We consider the half-filled case with the large on-site Coulomb repulsion Ud by using the variational Monte Carlo method. The ground state is insulating when Ud is large at half-filling. The ground state undergoes a transition from a metal to a Mott insulator when the level difference εp-εd is increased.

Josephson Fourier Spectrometer Based on HTSP: Construction and Quantum Computer Realization Problem

The possibility of creating a spectrometer of THz range, which is based on non-stationary Josephson effect in HTSP is considered. Simple design of Josephson junction adjustable at cryogenic conditions is proposed. Using of such device for solving the problem of factorization of high value numbers, which in fact is the only motivation for creating a quantum computer, is discussed.