Showing papers on "High-temperature superconductivity published in 2022"

Development of RE-Ba-Cu-O superconductors in the U.S. for ultra-high field magnets

Abstract: High-temperature superconductors (HTSs) make it possible to achieve magnetic fields beyond the 23.5 T limit of low-temperature superconductors. For higher energy density, high-performance HTS with J e > 1000 A mm−2 enables reduction in coil winding length and a smaller magnet size. Among HTS, REBa2Cu3O7−δ (REBCO, RE = rare earth) exhibits excellent mechanical properties and superior performance over a wide range of temperatures and magnetic fields. REBCO tapes can be converted to various formats, including round wires. The state-of-the-art REBCO superconductors for ultra-high field magnets, including cable/wire architectures, are reviewed. R&D needs to address the remaining challenges with REBCO superconductors for ultra-high magnetic field applications is discussed.

Progress on Second-Generation High-Temperature Superconductor Tape Targeting Resistive Fault Current Limiter Application

Abstract: The resistive superconducting fault current limiter is well known for its simple structure and outstanding current-limiting effect, and it is broadly applied in power grid systems. The second-generation high-temperature superconductor (HTS) tape, of higher structural strength and greater room-temperature resistance, is well suited for application in resistive superconducting fault current limiters. The quenching caused by overcurrent in the HTS tape is a complexed coupling effect of several physical factors. The tape structure and properties directly impact the ultimate HTS tape’s quench performance. In this study, various SS316-laminated HTS tapes, of different critical currents, room-temperature resistances, and masses, were prepared. The pulse impact parameters of the various tape samples were measured using the RLC high-current impact test platform. By analyzing the resultant data, a quantitative assessment methodology to measure a tape’s tolerance toward impact was developed. The dependence of the HTS tape’s tolerance toward impact on its critical current, room-temperature resistance, and mass was studied. This provides numerical guidance on HTS material selection for resistive superconducting fault current limiters.

Compressed superhydrides: the road to room temperature superconductivity

Abstract: Room-temperature superconductivity has been a long-held dream and an area of intensive research. The discovery of H3S and LaH10under high pressure, with superconducting critical temperatures (Tc) above 200 K, sparked a race to find room temperature superconductors in compressed superhydrides. In recent groundbreaking work, room-temperature superconductivity of 288 K was achieved in carbonaceous sulfur hydride at 267 GPa. Here, we describe the important attempts of hydrides in the process of achieving room temperature superconductivity in decades, summarize the main characteristics of high-temperature hydrogen-based superconductors, such as hydrogen structural motifs, bonding features, electronic structure as well as electron-phonon coupling etc. This work aims to provide an up-to-date summary of several type hydrogen-based superconductors based on the hydrogen structural motifs, including covalent superhydrides, clathrate superhydrides, layered superhydrides, and hydrides containing isolated H atom, H2and H3molecular units.

Dynamic Resistance of Series-Connected HTS Stacks Considering Electromagnetic and Thermal Coupling

Abstract: When a high temperature superconductor (HTS) coated conductor carries a DC transport current within the background of an oscillating magnetic field, the effect of dynamic resistance takes place. Under the circumstance when the dynamic resistance effect is significant, heat dissipation will be generated to change the temperature of HTS tapes. The amplitude of the instantaneous dynamic resistance increases with time due to the rising temperature. The phenomenon is more obvious when it comes to the HTS stacks where superconducting tapes are assembled so close. This paper proposes a numerical model with electromagnetic and thermal coupling to study the dynamic resistance of the series-connected HTS stack. Experimental results have shown that the proposed numerical model can describe dynamic resistance more accurately than conventional models. Besides, investigations are carried out on how the insulation thickness in the stack and the frequency of AC magnetic fields impact the dynamic resistance of HTS stacks under the influence of Joule heat. This can provide a useful reference for the design of superconducting devices in which dynamic resistance occurs.

A Review on Strain Study of Cuprate Superconductors

Abstract: Cuprate superconductors have attracted extensive attention due to their broad promising application prospects. Among the factors affecting superconductivity, the effect of strain cannot be ignored, which can significantly enhance or degrade superconductivity. In this review, we discuss and summarize the methods of applying strain to cuprate superconductors, strain measurement techniques, and the influence of strain on superconductivity. Among them, we pay special attention to the study of strain in high–temperature superconducting (HTS) films and coating. We expect this review can guide further research in the field of cuprate superconductors.

Progress and prospects for cuprate high temperature superconductors under pressure

Abstract: ABSTRACT Since the discovery of high temperature superconductivity in at an unprecedented of 35 K over 35 years ago, high pressure experiments have played a critical role in bdeveloping cuprate superconductivity. Soon after its discovery, compression experiments on revealed a large / , motivating the study of ‘chemical pressure’ in the material that led to the 90 K Superconductor . Cuprate superconductors discovered subsequently exhibited a range of from 30 K to 140 K, including the commonly studied Bi, Tl, and Hg based families. Pressure has large effects on superconductivity in these materials, including raising in the Hg based cuprates from 140 K to 166 K at 30 GPa. Reviewing past experiments indicate that pressure dopes holes into the planes common to all cuprates. Further detailed high pressure studies of these materials should deepen our understanding of cuprate superconductivity and the possibility of reaching still higher in cuprates.

Magnetization Loss of Multi-Layered CORC According to Various Winding Types

Abstract: Conductor on round core (CORC) is one of high temperature superconducting (HTS) conductors with large current capacity. CORC stacks HTS tapes to increase the current capacity. CORC can have various structures according to how we stack HTS tapes. The direction of the spiral winding in each layer and the overlapped area of HTS tapes affect AC losses of CORC because the losses mainly depend on the perpendicular magnetic fields on the HTS tapes. We have measured the magnetization losses of CORC short samples with various structures. Each sample has a different number of layers, winding direction in each layer, and overlapped area. We confirmed the best structure of CORC with the least magnetization loss.

Improvement of critical current density of <i>RE</i> Ba ₂ Cu ₃ O _7-δ by increase in configurational entropy of mixing

Abstract: REBa2Cu3O7-d (RE123, RE: rare earth) is one of the high-temperature superconductors with a transition temperature (Tc) exceeding 90 K. Because of its high Tc and large critical current density (Jc) under magnetic fields, RE123 superconductors have been expected to play a key role in superconductivity application. To accelerate application researches on RE123-based devices, further improvements of Jc characteristics have been desired. In this study, we investigated the effects of high-entropy alloying at the RE site on the superconducting properties, through the measurements of local (intra-grain) Jc (Jclocal) by a remanent magnetization method. We found that Jclocal shows a trend to be improved when four or five RE elements are solved at the RE site, which results in high configurational entropy of mixing (delta_Smix). Because high-entropy alloying can improve Jclocal of RE123 superconductors by modification of the RE site composition and delta_Smix, and the technique would be applicable together with other techniques, such as introduction of nanoscale disorders, our entropy-engineering strategy introduced here would be useful for development of RE123 superconducting materials available under high magnetic fields.

Three-Dimensional Numerical Characterization of High-Temperature Superconductor Bulks Subjected to Rotating Magnetic Fields

Abstract: High-temperature superconductor (HTS) bulks have shown very promising potential for industrial applications due to the ability to trap much higher magnetic fields compared to traditional permanent magnets. In rotating electrical machines, the magnetic field is a combination of alternating and rotating fields. On the contrary, all studies on electromagnetic characterization of HTS presented in the literature so far have only focused on alternating AC magnetic fields and alternating AC loss due to the unavailability of robust experimental techniques and analytical models. This paper presents a numerical investigation on the characterization of HTS bulks subjected to rotating magnetic fields showing AC loss, current density distribution in three-dimensional axes, and trapped field analysis. A three-dimensional numerical model has been developed using H-formulation based on finite element analysis. An HTS cubic sample is magnetized and demagnetized with two-dimensional magnetic flux density vectors rotating in circular orientation around the XOY, XOZ, and YOZ planes.

Influence of Ion Irradiation on Critical Characteristics of Second-Generation HTSC Tapes

Abstract: One of the practical applications of the second-generation HTSC tapes (or CC – coated conductors) is in accelerator magnets. During operation, the superconducting winding will inevitably be exposed to ionizing radiation with the formation of radiation defects in the HTSC layer. This process can lead to a gradual degradation of both the critical characteristics and the structure of the HTSC. The report presents the results demonstrating the change in the critical temperature and critical current (down to a complete loss of superconducting properties) of the second-generation HTSC tapes under irradiation with 6.3 MeV Cu ions in a wide range of fluences. The critical temperature was measured by a four-contact method. The critical current was calculated from the magnetization curves, which were measured in the temperature range from 5 to 77 K and magnetic fields up to 8 T. It was demonstrated that the critical current is more sensitive to radiation defects than the critical temperature is.

Pulsed Field Magnetization of YBa2Cu3O7-δ Bulk Assembly for Motor Application

Abstract: A high-temperature superconducting (HTS) motor has been developed using bulk superconductors as quasi-cryo-permanent magnets to allow a stronger remanent field. In this work, we focus on the in-situ magnetization of the bulk superconductors which is considered one of the main challenges. YBa2Cu3O7-δ bulks that had been used in the motor were magnetized via pulsed field magnetization (PFM) as single samples and assembly. The peak trapped field achieved via PFM is similar to that achieved via field cooling magnetization at 77 K. For the bulk assembly, the existence of a neighboring bulk superconductor was found to affect the penetration of the magnetic flux during the PFM process especially under low applied fields. This leads to a 3% to 4% reduction in peak trapped field, and 10% to 13% reduction in integrated magnetic flux.

Study on AC Over-Current Characteristics With Physical Properties of the Outer Layer of GdBa2Cu3O7-x Thin-Film-Type Superconducting Wire Having Composite Structure Using RF Sputtering Deposition Method

Abstract: Superconducting application technology, which is an eco-friendly core technology in the field of electric power and energy transport in the future industry, can be developed starting with the improvement of the performance of superconducting wires with excellent critical characteristics. A thin-film-type superconducting wire, which is created in the form of a multi-layered thin film, is a key element in superconducting power devices. Various surface treatment technologies can be applied to the stabilization layer among the multiple thin-film layers of thin-film-type superconducting wire, and a surface treatment technology using plasma can also be used. Surface treatment technology using plasma has already been applied to various materials as a means to improve the critical properties of materials. Based on these premises, this study sought to change the physical properties of thin-film-type superconducting wire by applying the plasma surface treatment technology to the stabilization layer of GdBa2Cu3O7-X thin-film-type superconducting wire, a core material for superconducting power devices. The changed electrical conduction characteristics are analyzed by measuring the critical currents of 8 specimens, as well as AC overcurrent, which is the main subject of this study. The findings of the test indicate that the electrical properties of the thin-film-type superconducting wire depend on the physical properties of the additionally deposited material. Accordingly, the electrical performance of the thin-film-type superconducting wire also varies. In addition, the plasma surface treatment technology is deemed suitable for the change in the electrical performance of thin-film-type superconducting wire.

Superconductivity Phenomenon: Fundamentals and Theories

Abstract: Since their discovery, superconductor materials have been the subject of extensive studies thanks to their original properties. Such materials are endowed by zero resistance at a low temperature making it possible to conduct the electric current without loss of energy. In addition, magnetic fields are deeply affected in superconductors, they can be canceled completely in the material, or they can be pinned in a so-called mixed zone where both superconducting and normal states co-exist. Thus, thorough knowledge of the phenomena which occur within these materials is very necessary to enlarge their fields of integration. According to BCS theory, the superconductivity phenomenon in low-temperature Superconductors (LTS) originates from the pairing of electrons through phonons. Thus, researchers try to explain superconductivity in HTS materials which helps to improve the performance of applications that use superconductors. Although the LTS materials are exploited intensively in many areas, the problem of cryogenics still faces their industrial emergence. The manipulation of superconductors cooled with liquid nitrogen (77 K) instead of liquid helium (4.2 K) opens up market opportunities for high-temperature superconductivity technology. Works devoted to improving the critical temperature in view of reaching room temperature superconductivity are in permanent progression.

Numerical and Experimental Study on Thermal Stability of BSCCO/REBCO Hybrid Tapes

Abstract: This paper studies the thermal stability of BSCCO (Bi-2223) /REBCO hybrid tapes with different stacking methods under various operating currents in liquid nitrogen (LN ₂ ) bath. The thermal stability of single REBCO tape and BSCCO tape are also studied as the comparison. A 3D numerical model considering the anisotropic thermal conductivity is established to calculate the normal zone propagation velocity (NZPV) and minimum quench energy (MQE) of different hybrid tapes, and the temperature distributions of the tapes are obtained as well. The experiments of thermal stability of single tape and RB hybrid tape are also carried out. Results show the hybrid tape has better thermal stability than the REBCO tape and faster NZPV than the BSCCO tape.

Multilayer YBa₂Cu₃O_7-x/Ca_0.3Y_0.7Ba₂Cu₃O_7-x Nanocomposite Films With 2–8% BaZrO₃ Doping for High-Field Applications

Abstract: High-field applications require high concentrations of strong pinning centers. In this article, BaZrO ₃ doped YBa ₂ Cu ₃ O ₇ (BZO/YBCO) nanocomposite films with BZO doping up to 8 vol.% were fabricated in a multilayer (ML) format by inserting two 10 nm thick Ca _0.3 Y _0.7 Ba ₂ Cu ₃ O _7-x spacer layers in the BZO/YBCO nanocomposite films for improved pinning and enhanced critical current density J_c at high fields. Significant J_c enhancement was observed in all the BZO/YBCO ML films of BZO doping in the entire range of 2–8 vol.% as compared to their SL counterpart's. At 65 K, the enhancement of peak pinning force density ( F_{p, max} ) is 71, 67, 296, and 47% for 2, 4, 6, and 8 vol.% BZO/YBCO ML films, respectively. In addition, the B _max (the location of the F_{p, max} ) is shifted towards higher values for BZO/YBCO ML films by up to 33%. Interestingly, at high BZO doping of 8 vol.%, the enhanced modulated strain field was found to reduce the detrimental effect of Ca ion diffusion on T _c , leading to J_c enhancement at a strong field up to 9 T at all orientations of the magnetic field.

Advances in second-generation high-temperature superconducting tapes and their applications in high-field magnets

Abstract: Second-generation high-temperature superconducting (2G-HTS) tapes based on REBa2Cu3O7-x (REBCO, RE: rare earth) materials enable the energy-efficient and high-power-density delivery of electricity, thereby promoting the development of clean energy generation, conversion, transmission, and storage. To overcome the weak grain-boundary connection and poor mechanical properties of these superconductors, a thin-film technology for epitaxy and biaxial textures based on flexible substrates has been developed. In recent years, high-quality 2G-HTS tapes have been produced at the kilometer scale and used in superconducting demonstration projects. This review first summarizes the development of HTS materials and briefly expounds the properties of REBCO superconducting materials. Subsequently, the structural characteristics, preparation methods, and current research progress of 2G-HTS tapes are given. In addition, the applications of REBCO tapes in constructing high-field magnets are also briefly reviewed.

Portable, desktop high-field magnet systems using bulk, single-grain RE–Ba–Cu–O high-temperature superconductors

Abstract: Bulk high-temperature superconducting materials can trap magnetic fields up to an order of magnitude larger than conventional permanent magnets. Recent advances in pulsed field magnetization (PFM) techniques now provide a fast and cost-effective method to magnetize bulk superconductors to fields of up to 5 T. We have developed a portable, desktop bulk high-temperature superconducting magnet system by combining advanced PFM techniques with state-of-the-art cryocooler technology and single-grain, RE–Ba–Cu–O [(RE)BCO, where RE is a rare-earth element or yttrium] bulk superconducting materials. The base temperature of the system is 41 K and it takes about 1 h for the system to cool down to 50 K from room temperature. A capacitor bank, combined with easily-interchangeable, solenoid- or split-type copper magnetizing coils and an insulated bipolar gate transistor acting as a high-speed switch, allows magnetic pulses to be generated with different pulse profiles. The system is capable of trapping magnetic fields of up to ∼3 T. In this work, we report the results of the magnetization of a range of single-grain Y–Ba–Cu–O, Eu–Ba–Cu–O and Gd–Ba–Cu–O (GdBCO), bulk superconducting discs using this system. A higher trapped field was recorded using a split coil incorporating iron yokes at temperatures of 65 K and above, whereas at lower temperatures, a higher trapped field was obtained using the solenoid coil. The GdBCO sample achieved the highest trapped field for both single-pulse (SP) and two-stage-multi-pulse (TSMP) methods using the solenoid coil. Maximum trapped fields of 2.26 T at 55 K and 2.85 T at 49 K were recorded at the centre of the top surface of the GdBCO sample for the SP and TSMP methods, respectively. The PFM process is substantially an adiabatic process so, therefore, the thermal contact between the sample and sample holder is of critical importance for cooling the bulk sample during application of the pulse. The design of the sample holder can be modified easily to enhance the thermal stability of the sample in order to achieve a higher trapped field.

High-Tc Cuprate Superconductors: Materials, Structures and Properties

Abstract: The cuprate superconductors are the first and the most important high-Tc superconducting materials, as still today applications of superconductivity at the temperature of liquid nitrogen (77 K) are only possible with cuprate superconductors (and here, especially the three compositions YBa2Cu3O7−δ (abbreviated as Y-123 or YBCO), Bi2Sr2CaCu2O8+δ (Bi-2212) and Bi2Sr2Ca2Cu2O10+δ (Bi-2223)). In this chapter, we present the crystal structures of the main 5 HTSc cuprate families (Ln-Cu–O (Ln-214), Y-Ba-Cu–O (YBCO), Bi-Sr-Ca-Cu–O (BSCCO), Tl-Ba-Ca-Cu–O (TlBCCO), and Hg-Ba-Ca-Cu–O (HgBCCO)) and their specific crystallographic features and discuss the resulting superconducting properties and the electric and magnetic characteristics being important for the applications, including the normal state properties, the grain boundary problem, the irreversibility lines, and issues of creating flux pinning sites to increase the critical current density, jc. We further point out the progress in the material development in the direction for applications concerning the microstructure and texture and present the typical sample shapes.KeywordsHigh-Tc superconductorsCupratesCrystal structuresPhase diagramDopingOxygen contentIrreversibility linesMicrostructureApplications

Graphene doping effects on the magnetic and transport properties of YBa2Cu3O7-δ high temperature superconductor

Abstract: In this work, bulk graphene-doped YBa 2 Cu 3 O 7-δ (YBCO) high-temperature superconductor samples were prepared with composition of YBCO + x wt.% graphene nanoplatelets (G) (x = 0, 0.2, 0.4, 0.6, 0.8, 1.0). The X-ray diffraction patterns show the YBCO orthorhombic phase in all the samples. The SEM images show good grain connectivity between YBCO grains in graphene-doped samples. Furthermore, the broadening of resistivity under applied magnetic fields up to 9T and thermally activated flux creep in the mixed state were studied using Arrhenius plots. The activation energy U 0 (H) increased with graphene doping results in better flux pinning and higher critical current densities. Moreover, improvement in the critical temperature (T C ), upper critical field (μ 0 H C2 ) and the irreversibility field (μ 0 H irr ) were observed in graphene-doped samples as compared to the pure YBCO sample.

Influence of growth temperature on the pinning landscape of YBa2Cu3O7− δ films grown from Ba-deficient solutions

Abstract: Cuprate coated conductors are promising materials for the development of large-scale applications, having superior performance over other superconductors. Tailoring their vortex pinning landscape through nanostructure engineering is one of the major challenges to fulfill the specific application requirements. In this work, we have studied the influence of the growth temperature on the generation of intrinsic pinning defects in YBa2Cu3O7−δ films grown by chemical solution deposition using low Ba precursor solutions. We have analysed the critical current density as a function of the temperature, applied magnetic field magnitude and orientation, J c(T,H,θ), to elucidate the nature and strength of pinning sites and correlate the microstructure of the films with their superconducting performance. An efficient pinning landscape consisting of stacking faults and associated nanostrain is naturally induced by simply tuning the growth temperature without the need to add artificial pinning sites. Samples grown at an optimized temperature of 750 °C show very high self-field J c values correlated with an overdoped state and improved J c(T,H,θ) performances.

Online Perception on the Performance of YBCO Tapes via Intelligent Video-Aided PLD System

Abstract: Second generation HTS tape has entered the stage of mass production. The biggest bottleneck in stable production and consistently high-quality superconducting coatings lies in the control of deposition temperature during superconducting coatings. It is very challenging to effectively monitor the temperature in the dynamic process of roll-to-roll coating. Through observation, it is found that the color of superconducting surface is very sensitive to the change of coating temperature. In this study, a real-time video analysis technology has been developed to obtain the grayness scale of the surface of the superconducting layer during coating. The relationship between grayness scale, temperature and the final critical current of superconducting tape has been established through short sample experiments. These relationships are also clearly demonstrated in the long tape production process, which can significantly detect any abnormal trends of tape products by capturing the surface temperatures through grayness scale. The region of interest was tracked, by dividing it into three parts and calculating the average grayness level of each part. The results obtained can be used to determine PLD temperature setting and provide a reference for the subsequent slitting of superconducting tapes. This work also provides a potential quality improvement technique for superconducting tape production.

Enhancement of Bi-2223 Intergrain Connections by Heat Treatment Parameters Optimization

Abstract: Aiming at the improvement of current capacity in Bi2Sr2Ca2Cu3O10+δ (Bi-2223) superconducting tapes, both the calcination process of precursor powders and the sintering process of Bi-2223 tapes have been modified to tune the intergrain connections. By adopting different calcination atmosphere of air and oxygen during the pre-calcination process, the phase composition of final precursor powder kept almost the same, while the particle size decreased in oxygen pre-calcinated powders, which thus led to the appearance of more secondary phases. On the other hand, due to the optimization of crystallization process of Bi-2223 phase, the microstructure with less pore density has been obtained, which proved that the increase of heating rate could obviously lead to the enhancement of intergrain connections of Bi-2223 tapes. Finally, critical current of 116 A has been achieved with the air pre-calcinated powders and 400 °C /h heating rate during HT2, which was ∼40% increase comparing with the Ic of Bi-2223 tape with oxygen pre-calcinated powders and 100 °C/h heating rate in HT2 process.

Superconductor relaxation -- A must to be integrated into stability calculations

Abstract: A superconductor is stable if it does not quench. Quench is a short-time physics problem. For its deeper understanding of, and how to avoid quench, the physics behind stability has to be analysed. A previously suggested dynamic relaxation model is re-considered and applied to YBaCuO 123 and BSCCO 2223 high-temperature, thin film superconductors. Parallel to this investigation, an unconventional approach using an electrical resistance network (a cell model) is applied to introduce a method how to estimate the extent by which, in resistance measurements, exact determination of critical temperature of superconductors is possible. This resistive cell model, when considering its numerical convergence behaviour, in a side result may provide an alternative explanation of (at least a contribution to) bending of resistivity vs. temperature curves, and perhaps also an alternative to standard explanations of the thermal fluctuations impact on these curves. The dynamic relaxation and the resistance models provide a parenthesis that correlates, in terms of the Ginzburg-Landau order parameter, (i) solution of superconductor stability problem (the main objective of this paper), with tentative explanation of (ii) bending of the resistivity curves near critical temperature and (iii) with predictions from thermal fluctuations.

The Simulation on Thermal-Electromagnetism of High-Tc Superconducting Bulks Under Stochastic Excitations

Abstract: High temperature superconducting (HTS) maglev utilizes the magnetic flux pinning characteristics of vehicle's high temperature superconducting bulk to achieve the stable suspension. During the operation, ac losses will occur inside the HTS bulks due to the irregularity of the permanent magnetic guideway (PMG), causing the change of the temperature, which directly affects the stability of the suspension system. In this article, the magnetic-thermal-guideway coupled model of two-dimensional HTS bulks YBCO, liquid nitrogen (LN) and PMG is established by using COMSOL Multiphysics. The test track irregularity spectrum of high-speed railway is introduced and added to the PMG to simulate the magnetic field fluctuation caused by its arrangement irregularity. The characteristics of the HTS bulks’ power loss, the average current density distribution over the cross section and the temperature rise of the bulk, LN, and suspension gap (SG) are studied respectively under four conditions of excitations: lateral coupled with vertical excitations, lateral excitations, vertical excitations, and nonexcitations. Meanwhile, by comparing and analyzing with the model without considering the temperature, the influence of the temperature on the current density is studied. These results provide certain references for the safe and stable operation of HTS suspension system.

High Temperature Superconductivity Arising in a Metal Sheet Full of Holes

Abstract: By drilling periodic thru-holes in a suspended film, the phonon system can be modified. Being motivated by the BCS theory, the technique, so-called phonon engineering, was applied to a niobium sheet. The newly emergent high-Tc superconductivity, however, cannot be accounted for by the BCS theory. Rather, its exposed configuration, namely a square-lattice oxygen network, is reminiscent of the copper--oxygen plane in cuprate high-Tc superconductors. It turns out that its magnetic result is consistent with the principle of giant atom, which was developed by another heroes of superconductivity, Fritz London and John Slater, in the 1930s, several decades earlier than the propagation of BCS theory. The superconducting transition feature is discussed on the basis of a comprehensive theory of the giant atom---the theory of hole superconductivity.

Variation of restoring force characteristics with the arrangement of high-temperature superconductors

Abstract: In this study, we investigated the characteristic changes in the restoring force characteristics with magnetic flux pinning phenomenon caused by changing the boundary conditions between multiple high-temperature superconductors. The magnetic flux pinning characteristics were investigated when a gap was provided between the superconductors and when a step was provided between the superconductors. At this time, a permanent magnet with a magnetic flux focusing arrangement was used as the floating body. As a result, it was confirmed that the restoring force characteristics due to magnetic flux pinning are improved under specific conditions. This revealed the usefulness of adjusting the boundaries between superconductors.

Basic Concepts and Properties of Superconductors

Abstract: The phenomenon of super conductance is quite fascinating due to enormous applications and hence intense research in this area attracted engineers, scientists and businessmen. In this Chapter, we will briefly elaborate the conversion of a normal conductor to a superconductor which is a fascinating material since its discovery as well as the role of critical temperature and critical magnetic field for the super phenomenon of superconductivity. A short historical journey of superconductors from 1911 to date is also the part of this chapter that started with the work of Onnes on extreme low temperatures in cryogenic laboratories. The difference between perfect conductor and superconductor, classification of superconductors and finally the fundamental properties of superconductors have been discussed precisely.