Superconductivity In Materials Research Articles

Fabrication of a 25.2 T NMR magnet for an extreme condition user facility in China

Abstract An ultra-high field magnet (> 20 T) is desirable to study material characteristics under extreme magnetic condition with the use of magnetic resonance for a higher signal-to-noise ratio, better sensitivity and a higher spectral resolution. The fabrication of an ultra-high field magnet requires high-temperature superconducting materials like REBSO and BSCCO, which have higher critical temperature and current density as compared to conventional low-temperature superconducting materials. Despite the benefits of BSCCO for better field homogeneity and stability due to its smaller screening currents, it is technically challenging to use it in magnet fabrication due to the greater variations in tape thickness and width. In this highlighted study, an optimization procedure was developed to randomly re-order the wound double-pancake coils as well as optimize the winding turns based on pre-winding measurements. Such optimizations enable the fabrication of a magnet with high homogeneity that is suitable for use in nuclear magnetic resonance.

Recent development in high temperature superconductor: Principle, materials, and applications

Superconducting materials, discovered in the early twentieth century, have fascinated scientists with their unique attributes. This review provides a thorough exploration of superconductivity, tailored for newcomers, aiming to be a foundational resource for future research. It traces the evolution of different superconductors, including traditional, cuprate, and non-copper oxide types, detailing their specific characteristics. Central to the review is the examination of theoretical foundations, particularly the BCS theory, and the diverse applications of superconductors in high-performance magnets, energy transmission, and quantum computing. However, the practical deployment of superconductors is limited by challenges, notably their operation at extremely low temperatures, hindering widespread use. Furthermore, economic and technical difficulties in production and maintenance persist. To advance superconductors' potential, research must focus on enhancing critical temperatures and current density and developing cost-effective manufacturing techniques. This will enable novel applications in energy, transportation, and healthcare, driving technological progress.

Publishing important work that lacks validity or reproducibility – pushing frontiers or corrupting science?

ABSTRACT Scientific research requires objectivity, impartiality and stringency. However, scholarly literature is littered with preliminary and explorative findings that lack reproducibility or validity. Some low-quality papers with perceived high impact have become publicly notable. The collective effort of fellow researchers who follow these false leads down blind alleys and impasses is a waste of time and resources, and this is particularly damaging for early career researchers. Furthermore, the lay public might also be affected by socioeconomic repercussions associated with the findings. It is arguable that the nature of scientific research is such that its frontiers are moved and shaped by cycles of published claims inducing in turn rounds of validation by others. Using recent example cases of room-temperature superconducting materials research, I argue instead that publication of perceptibly important or spectacular claims that lack reproducibility or validity is epistemically and socially irresponsible. This is even more so if authors refuse to share research materials and raw data for verification by others. Such acts do not advance, but would instead corrupt science, and should be prohibited by consensual governing rules on material and data sharing within the research community, with malpractices appropriately sanctioned.

Excess Conductivity Analysis of an YBCO Foam Strut and Its Microstructure.

Struts of a superconducting YBa2Cu3Oy (YBCO) foam prepared by the infiltration growth method on the base of commercial polyurethane foams were extracted from the bulk, and thoroughly characterized concerning the microstructure and the magnetoresistance, measured by the four-point technique. Optical microscopy, electron microscopy, electron backscatter diffraction and atomic force microscopy observations indicate a unique microstructure of the foam struts which shows a large amount of tiny Y2BaCuO5 (Y-211) particles (with diameters between 50 and 100 nm) being enclosed in channel-like grain boundaries between the YBCO grains and a one-of-a-kind surface of the struts covered with Ba3Cu5Oy-particles. The resistance data obtained at temperatures in the range 4.2 K ≤T≤ 150 K (applied magnetic fields ranging from 0 to 7 T) were analyzed in the framework of the fluctuation-induced conductivity (FIC) approach using the models of Aslamazov-Larkin (AL) and Lawrence-Doniach (LD). The resulting FIC curves reveal the presence of five distinct fluctuation regimes, namely, the short-wave (SWF), one-dimensional (1D), two-dimensional (2D), three-dimensional (3D), and critical (CR) fluctuation domains. The analysis of the FIC data enable the coherence length in the direction of the c-axis at zero-temperature (ξc(0)), the irreversibility field (Birr), the upper critical magnetic field (Bc2), the critical current density at T= 0 K (Jc(0)) and several other parameters describing the the material's superconducting properties to be determined. The present data reveal that the minuscule Y-211 particles found along the YBCO grain boundaries alter the excess conductivity and the fluctuation behavior as compared to conventional YBCO samples, leading to a quite high value for Jc(0) for a sample with a non-optimized pinning landscape.

Interpretably learning the critical temperature of superconductors: Electron concentration and feature dimensionality reduction

A machine learning model for predicting the critical temperature of novel superconductors is proposed. The novelty of this approach is based solely on the choice of ab initio features, that is, descriptors directly and solely related to the electronic and atomic information of the single elements that chemically bond to form superconductors. We could show that selecting features, such as the electron concentration in the materials and the electronegativity from the available superconductor data, allows for a significant reduction in the learning dimensionality. At the same time, this choice provides a prediction accuracy in critical temperature up to 93% (relevant to a mean absolute error of 4.2 K) similar to more complex models using a significantly higher feature space. In total, the features could be reduced down to 11 in addition to the multidimensional electronic concentration (including 17 features for the atomic orbitals), emphasizing the significantly higher importance of electronegativity and electron concentration. The latter is mainly influenced by the 3s orbital followed by the 3p orbital. This choice is physically intuitive as it directly links to the electronic orbitals in the superconductors that mostly influence the learning, thus defining the accuracy of the predicted critical temperature. At the same time, the learning process is interpretable, providing a deep insight that could be proven invaluable in developing new theories on novel superconductor materials.

On the Structural and Vibrational Properties of Solid Endohedral Metallofullerene Li@C60

The endohedral lithium fulleride, Li+@C60•−, is a potential precursor for new families of molecular superconducting and electronic materials beyond those accessible to date from C60 itself. Solid Li@C60 comprises (Li@C60)2 dimers, isostructural and isoelectronic with the (C59N)2 units found in solid azafullerene. Here, we investigate the structural and vibrational properties of Li@C60 samples synthesized by electrolytic reduction routes. The resulting materials are of high quality, with crystallinity far superior to that of their antecedents isolated by chemical reduction. They permit facile, unambiguous identification of both the reduced state of the fulleride units and the interball C-C bonds responsible for dimerization. However, severe orientational disorder conceals any crystal symmetry lowering due to the presence of dimers. Diffraction reveals the adoption of a hexagonal crystal structure (space group P63/mmc) at both low temperatures and high pressures, typically associated with close-packing of spherical monomer units. Such a situation is reminiscent of the structural behavior of the high-pressure Phase I of solid dihydrogen, H2.

Experimental study on the an-isotropic critical current of REBCO tape.

Superconducting magnets are widely used in nuclear fusion reactors, high-energy particle accelerators, steady-state high magnetic fields, etc. Higher magnetic fields and higher operating temperatures are two application trends. High temperature superconducting (HTS) materials are the only choice for high temperature and high field magnets in the future. The first- and second-generation HTS materials have a typical tape structure; their critical performance is magnetic field angle and temperature dependent. A new test facility is developed for an experimental study on the an-isotropic critical current. The field angle can be changed from 0° to 360° with a resolution of 1°. The rotation deviation angle is measured to be 0.2° when the upper part rotates 90°. The temperature can be changed from 4.2 to 80K. The temperature errors are ±50, ±80, and ±135 mK for 4.2-20, 20-40, and 40-80K, respectively. The angle dependence of critical current (Ic) of the tested rare-earth barium copper oxide tape within 0°-30° is strong. From 30° to 90°, the sample Ic almost does not change with the magnetic field angle. The implementation of the project will not only promote the structural optimization of HTS tapes but also promote the miniaturization and economical application of HTS magnets.

Radiation protection methods for suborbital aircrafts

This paper presents the outcomes of a study conducted by SALTO team in the framework of the Student Aerospace Challenge, focusing on designing structures to optimize passenger protection against radiation in a suborbital vehicle. The study delves into space radiation characteristics and their potential impact on human health during suborbital flights. Through comprehensive research and the utilization of CARI-7A software, the team evaluated radiation exposure and explored both passive and active shielding solutions. The passive shielding solution involved the design of a multifunctional sandwich panel and a shielding layout for windows, minimizing weight penalties on the vehicle’s structure. Additionally, an active shielding concept utilizing high-temperature superconductor material and solenoid layouts was investigated. The study underscores the benefits and challenges associated with both passive and active shielding methods, emphasizing the importance of further exploration to enhance suborbital flight safety and pave the way for future human space exploration endeavors.

TMR-high-temperature superconductor composite magnetic sensor and its performance optimization

Tunnel magnetoresistance (TMR), recognized for its high sensitivity and low power consumption, holds significant promise in the domain of weak magnetic field detection. Using superconducting materials as magnetic concentrators can achieve several hundred to even a thousandfold amplification of magnetic fields, making it one of the most effective approaches to enhance the magnetic field resolution of TMR sensors. This paper utilized the flip-chip bonding process to integrate TMR with the high-temperature superconductor YBCO (YBa2Cu3O7-δ), and successfully developed TMR-YBCO composite magnetic sensor. Building upon this foundation, through optimization of the fabrication process and the pioneering use of a structural design incorporating the filling of annular holes with superconducting concentrators, the sensitivity of the sensor was further enhanced. Finally, the magnetic field resolution was increased by 1030 times compared to TMR sensors, reached to 2.9pT/Hz1/2 at 1 Hz. Simultaneously, results from frequency band testing indicated excellent frequency band characteristics, with a frequency response range exceeding kHz.

Prediction of ambient pressure superconductivity in cubic ternary hydrides with MH6 octahedra

Exploring high-temperature superconducting (high-Tc) material at ambient pressure holds immense significance for physics, chemistry, and materials science. In this study, we perform a high-throughput screening of strong electron-phonon interactions in X2MH6 compounds (X = Li, Na, Mg, Al, K, Ca, Ga, Rb, Sr, and In; M are 3d, 4d, and 5d transition metals). These compounds have a cubic structure featuring an MH6 octahedron motif. Our screening calculations suggest that 26 compounds exhibit dynamic stability and strong electron-phonon coupling. Among them, Mg2RhH6, Mg2IrH6, Al2MnH6, and Li2CuH6 show promising energetic stability and Tc of more than 50 K at ambient pressure. This study underscores promising high-Tc compounds at ambient pressure with distinctive MH6 motifs.

Cryogen-free 400-MHz nuclear magnetic resonance spectrometer as a versatile tool for pharmaceutical process analytical technology.

The discovery of new ceramic materials containing Ba-La-Cu oxides in 1986 that exhibited superconducting properties at high temperatures in the range of 35 K or higher, recognized with the Nobel Prize in Physics in 1987, opened a new world of opportunities for nuclear magnetic resonance (NMRs) and magnetic resonance imaging (MRIs) to move away from liquid cryogens. This discovery expands the application of high temperature superconducting (HTS) materials to fields beyond the chemical and medical industries, including electrical power grids, energy, and aerospace. The prototype 400-MHz cryofree HTS NMR spectrometer installed at Amgen's chemistry laboratory has been vital for a variety of applications such as structure analysis, reaction monitoring, and CASE-3D studies with RDCs. The spectrometer has been integrated with Amgen's chemistry and analytical workflows, providing pipeline project support in tandem with other Kinetic Analysis Platform technologies. The 400-MHz cryofree HTS NMR spectrometer, as the name implies, does not require liquid cryogens refills and has smaller footprint that facilitates installation into a chemistry laboratory fume hood, sharing the hood with a process chemistry reactor. Our evaluation of its performance for structural analysis with CASE-3D protocol and for reaction monitoring of Amgen's pipeline chemistry was successful. We envision that the HTS magnets would become part of the standard NMR and MRI spectrometers in the future. We believe that while the technology is being developed, there is room for all magnet options, including HTS, low temperature superconducting (LTS) magnets, and low field benchtop NMRs with permanent magnets, where utilization will be dependent on application type and costs.

Superconductivity and stability of the novel electron-doped H3S system under high pressure

As promising candidate materials for high-temperature superconductors, hydrides have attracted much attention. In particular, the discovery of Im3¯m H3S with a high Tc of 203 K has set off an upsurge in hydride research. As an electron donor, the incorporation of metal in binary polyhydrides is believed to play an important role in stabilizing the crystal structure and improving superconductivity. The novel Pm3¯m H3SM (M=K, Rb, Sr, Tl, Cs, Ba) systems, which can be regarded as electron-doped Im3¯m H3S, are discovered to be dynamically and thermodynamically stable under pressure. Unfortunately, their superconductivity is not as good as that of the parent H3S. As the most promising superconductor among them, H3STl is predicted to be superconducting with a Tc of 111.7 K under 160 GPa. These findings reveal the intricacy of electron doping in modulating the superconductivity of hydrogen-based superconductors. Electron-phonon coupling (EPC) is found to have a negative correlation with the central frequency ωc of phonon, which opens new avenues for designing and optimizing novel high-Tc superconductors.

Unraveling the electronic structure of LuH, LuN, and LuNH: building blocks of new materials.

Advances in superconductor technology have been pursued for decades, moving towards room temperature models, such as a postulated nitrogen-doped lutetium hydride network. While experimental observations have been contradictory, insight into the building blocks of potential new superconductor materials can be gained theoretically, unravelling the fascinating electronic structure of these compounds at a molecular level. Here, the fundamental building blocks of lutetium materials (LuH, LuN, and LuNH) have been examined. The structures, spectroscopic constants for the ground and excited states, and the potential energy curves have been obtained for these species using complete active self-consistent field (CASSCF) and multireference configuration interaction with Davidson's correction (MRCI+Q) methods. For LuNH, the energetic properties of its isomers are determined. The bond dissociation energies of the three building blocks are calculated with the state-of-the-art f-block ab initio correlation consistent composite approach (f-ccCA) and the high accuracy extrapolated ab initio thermochemistry (HEAT) scheme. As well, an analysis of different formation pathways of LuNH has been provided.

A systematic study on the phase diagram and superconductivity of ternary clathrate Ca-Sc-H at high pressures.

This work explores potential high-temperature superconductor materials in hydrogen-rich systems. Here, the crystal structure stabilities of ternary Ca-Sc-H systems under high-pressure (P = 100-250 GPa) and their superconductivities are investigated using the particle swarm optimization methodology combined with first-principles calculations. For the predicted candidate structures of Ca-Sc-H systems, the pressure-dependent phase diagram and thermodynamic convex hull were investigated across a wide range of compositions; the electronic properties of all the predicted phases were analyzed in detail to study the bonding behavior of these stable phases. We identified the crystal structures of four thermodynamically stable compounds: R3̄m-CaScH6, Immm-CaSc2H9,C2/m-Ca2ScH10, and R3̄m-CaScH12. Among them, R3̄m-CaScH12 was predicted to have the highest Tc value (i.e., 173 K) at 200 GPa. The discovery of this previously unreported pressure-induced decomposition of Ca-Sc-H systems will pave the way for investigations on the nature of hydrogen-metal interactions.

Effect of doping on evolution of He<sup>+ </sup>ion irradiation defects and superconductivity in EuBa<sub>2</sub>Cu<sub>3</sub>O<sub>7–δ</sub> superconducting strips

Rare-earth barium copper oxide (REBCO) as a representative of the second-generation high-temperature superconducting materials possesses superior physical advantages such as high critical magnetic field, elevated critical temperature, and superior current density, which has been applied to many domains. Although the introduction of non-superconducting nanoscale particle dopants, as a critical method, can enhance the magnetic flux pinning capability of REBCO strips, the effect of the doping on the performance change and microstructure evolution of the strips under irradiation is ignored. In this work, undoped and 3.5 mol% BaHfO<sub>3</sub> (BHO) doped EuBa<sub>2</sub>Cu<sub>3</sub>O<sub>7–δ</sub> strips are investigated in the room-temperature irradiation experiments (1.4 MeV He<sup>+</sup> ions) with three distinct doses of 5×10<sup>14</sup>, 5×10<sup>15</sup>, and 5×10<sup>16</sup> ions/cm<sup>2</sup>, respectively. Electrical performance tests reveal that the undoped strips exhibit a slight increase in <i>J</i><sub>c</sub> after the low-dose irradiation. However, with dose increasing, <i>J</i><sub>c</sub> decreases by over 60%. In contrast, doped strips experience a significantly smaller decline in <i>J</i><sub>c</sub>, ranging only between 30% and 40% at high-dose irradiation. Raman spectroscopy and transmission electron microscopy characterizations confirm that the defects induced by He<sup>+</sup> ion irradiation lead to amorphization and structural disorder within the superconducting layers, which is the primary reason for the decline in the superconducting properties of the strips. The results show that the introduction of localized strain through BHO nanophase in the superconducting layer changes the migration and aggregation behavior of irradiation-induced defects, repairing the damaged superconductor structure. Furthermore, the field dependence and temperature dependence of <i>J</i><sub>c</sub> of doped strips are irradiation-resistant due to BHO nanocrystals as strong pinning centers. Additionally, unlike the superconducting properties of the REBCO strips that can be repaired through oxygen annealing after neutron or heavy ion irradiation, the electrical properties of the two types of strips irradiated with high doses of He<sup>+</sup> ions in this work are further deteriorated after being annealed. It is worth noting that compared with the undoped strip, the localized strain generated by BHO in the doped strip inhibits the size growth of helium defects in the three-dimensional direction at high temperatures, which changes the magnetic flux pinning characteristics and delays the disorder and amorphization of the superconducting layer structure caused by the severe growth of helium bubbles. This study provides a reference for the application of REBCO superconducting strips in the irradiation environment.

Enhancing Adrenaline Sensing with Lanthanum Cuprate: A Promising Approach for a Novel Sensor

Electrochemical sensing is an excellent analytical means with multiple applications. Most of the electrochemical developments are based on the novel electrochemically active substrates. A lot of them have been adopted from other fields of material science. Every new class of functional materials has impacted on the development of electroanalytical chemistry. In this view, lanthanide cuprates, a well recognized high temperature superconducting materials were considered for adrenaline sensing. Obtained from corresponding oxides, a highly crystalline La2CuO4 found to be a suitable substrate for analytical method development. It inherited sponge-like morphology common for the most of the previously reported lanthanum cuprates with narrow pore size distribution at 400–700 nm. Excellent charge mobility and low resistivity provided a carbon paste electrode with improved linearity range and low limit of detection. Repeatability and stability of the developed sensor were at satisfactory level. Sensor functionality was verified on the real samples with excellent recovery rates. With this work we suggest further development of electroanalytical methods with application of lanthanide cuprates.

Overall design of a 5 MW/10 MJ hybrid high-temperature superconducting energy storage magnets cooled by liquid hydrogen

The integration of superconducting magnetic energy storage (SMES) into the power grid can achieve the goal of storing energy, improving energy quality, improving energy utilization, and enhancing system stability. The early SMES used low-temperature superconducting magnets cooled by liquid helium immersion, and the complex low-temperature cooling system greatly limited the promotion and application of such devices. SMES based on high temperature superconductivity (HTS) materials can operate in the temperature range of 15–30 K, which simplifies the cooling system and reduces the cooling loss, and greatly improves the operating efficiency and stability of the cooling system. In this paper, the overall design of a 5 MW/10 MJ SMES based on state of the art HTS materials is achieved. The structural parameters of YBCO and MgB2 cables are introduced and the structural parameters of energy storage magnet are analyzed. And the cooling scheme for SMES is provided.

In-field electro-magnetic-force characteristics of high-temperature superconducting films containing cracks

Superconducting materials have so far been applied in the fields of superconducting motors, flux pumps and nuclear magnetic resonance, but they are prone to mechanical damage due to their material properties. In this paper, the influences of different crack types (including position, angle, size, quantity and spacing) on the characteristics of current-carrying and excited superconducting thin films are analyzed by numerical simulations, as well as their electromagnetic and mechanical characteristics. Several novel and important conclusions are found. In both states, the boundary crack presents the largest current density concentration, while the central crack produces the largest stress concentration. With the increase of crack spacing, the current density on the multi-crack film decreases and eventually tends to be stable. In the current-carrying state, compared with 3 mm cracked film, the current density of 1 mm cracked film is reduced by up to 62.5 %. The von Mises stress of high-temperature superconducting film with 0.1 mm single-spacing cracks is 22.5 % higher than that for 0.3 mm double-spacing cracks, which indicates that close spacing and a high number of crack types are most detrimental to the mechanical properties of high-temperature superconducting films. In the excited state, when the crack angle θ is 90°, the current density streamlines cannot be segmented effectively, which results in the current distribution trend closer to the defect-free film. A large amount of induced current flows into the low-flux region at the 3 mm crack, leading to an increased risk of film quench. The films with 1 mm single-spacing and double-spacing cracks form a low-flux region between the cracks, which makes the magnetic field more difficult to penetrate.

Green-Light GaN p-n Junction Luminescent Particles Enhance the Superconducting Properties of B(P)SCCO Smart Meta-Superconductors (SMSCs)

Superconducting materials exhibit unique physical properties and have great scientific value and vast industrial application prospects. However, due to limitations, such as the critical temperature (TC) and critical current density (JC), the large-scale application of superconducting materials remains challenging. Chemical doping has been a commonly used method to enhance the superconductivity of B(P)SCCO. However, satisfactory enhancement results have been difficult to achieve. In this study, we introduce green-light GaN p-n junction particles as inhomogeneous phases into B(P)SCCO polycrystalline particles to form a smart meta-superconductor (SMSC) structure. Based on the electroluminescence properties of the p-n junction, the Cooper pairs were stimulated and strengthened to enhance the superconductivity of B(P)SCCO. The experimental results demonstrate that the introduction of inhomogeneous phases can indeed enhance the critical temperature TC, critical current density JC, and complete diamagnetism (Meissner effect) of B(P)SCCO superconductors. Moreover, when the particle size of the raw material of B(P)SCCO is reduced from 30 to 5 μm, the grain size of the sintered samples also decreases, and the optimal doping concentration of the inhomogeneous phases increases from 0.15 wt.% to 0.2 wt.%, further improving the superconductivity.

Non-equilibrium dynamics of spin-lattice coupling

Quantifying the dynamics of normal modes and how they interact with other excitations is of central importance in condensed matter. Spin-lattice coupling is relevant to several sub-fields of condensed matter physics; examples include spintronics, high-Tc superconductivity, and topological materials. However, experimental approaches that can directly measure it are rare and incomplete. Here we use time-resolved X-ray diffraction to directly access the ultrafast motion of atoms and spins following the coherent excitation of an electromagnon in a multiferroic hexaferrite. One striking outcome is the different phase shifts relative to the driving field of the two different components. This phase shift provides insight into the excitation process of such a coupled mode. This direct observation of combined lattice and magnetization dynamics paves the way to access the mode-selective spin-lattice coupling strength, which remains a missing fundamental parameter for ultrafast control of magnetism and is relevant to a wide variety of materials.