High Critical Temperature Research Articles

Performance study of REBCO multi-filament tapes/CORC cables prepared by reel-to-reel mechanical incision

REBCO high-temperature superconductor (HTS) has widely used in high magnetic field applications, because of the excellent critical current properties and high critical temperature. However, REBCO tape has an extremely large width-to-thickness ratio (typically in the range of 1000–10000) to cause too high power dissipation in the applications. In order to reduce the shielding current effect and AC loss generated during the application of REBCO HTS tapes, a roll-to-roll mechanical incision device was developed for the preparation of REBCO multi-filaments tapes. The microscopic morphology, critical current IC, and hysteresis loss of the tapes before and after incision were comparatively characterized using optical microscope, standard four-probe method, and physical property measurement system (PPMS) and other equipment and methods. The results show that the developed device prepares multi-filaments tapes with incision grooves depths of ∼ 30 μm and grooves widths of ∼ 20 μm on the superconducting layer, and the hysteresis loss of the 3-filaments is reduced by up to 48.6 % compared to that of the non-striated tapes under different temperature conditions. In addition, the IC of the short samples of the 3-filaments tapes was reduced by ∼ 18 % compared with that of the non-striated tapes under 77 K and self-field test conditions, whereas the samples of the 3-filaments tapes and the non-striated tapes were hand-wound respectively onto a metal core with a diameter of 5.25 mm to make a single-layer CORC cable, and there was no significant reduction in the IC of either of them.

Superconductivity of amorphous and crystalline Re–Lu films

We report on superconducting properties of a novel material: rhenium-lutetium films. Different compositions of Re x Lu binary are explored from x ≈ 3.8 to close to pure Re stoichiometry. The highest critical temperature, up to Tc≈ 7 K, is obtained for x ≈ 10.5 in accordance with electron dispersive spectroscopy results. Depending on the deposition conditions, polycrystalline or amorphous films are obtainable, both of which are interesting for practical use. Crystalline structure of polycrystalline phase is identified as a non-centrosymmetric superconductor using grazing incidence x-ray diffractometry. Superconducting properties were characterized both resistively and magnetically. Magnetoresistivity and AC/DC susceptibility measurements allowed us to determine Hc1 and Hc2 of these films, as well as estimate coherence length ξ(0) and magnetic penetration depth λL(0) . We also provide information on surface morphology of these films. Demonstration of superconductivity in this material justifies the point of view that Lu plays a role of group 3 transition metal in period 6 of the Periodic table of elements. Then, in analogy with Re–Nb, Re–Ti, Re–Hf and Re–Zr, one can expect that crystalline Re–Lu also breaks time-reversal symmetry. If that is proven by future experiments, in combination with noncentrosymmetric feature, these films could be used for forming nonreciprocal current devices, such as superconducting diodes, without involvement of external magnetic fields.

High-temperature superconductivity in La4H23 below 100 GPa

High-temperature superconductivity has been observed in binary hydrides such as LaH10 at pressures close to 180GPa, whereby hydrogen cagelike structures have been identified as a common motif beneficial for high critical temperatures Tc. Efforts are now focused on finding hydride high-temperature superconductors at lower pressures. We present evidence for high-temperature superconductivity in binary La4H23 at a pressure of P=95GPa, with A15-type arrangement of the lanthanum atoms in the type-I clathrate structure. We synthesize La4H23 from a lanthanum film capped with a palladium catalyst promoting the dissociation of hydrogen. In resistance measurements, we observe superconductivity with a transition temperature Tc∼90K. The A15-type lanthanum sublattice is identified in x-ray diffraction on the same sample, in agreement with previous x-ray diffraction and structure prediction studies. Our study reinforces the favorability of cagelike networks of the hydrogen lattice for high-temperature superconductivity. Published by the American Physical Society 2024

Development of a novel fabrication technique for high-quality Bi-2223 bulks with high superconducting performance

The superior intergranular connectivity and strong flux pinning are indispensable for achieving high current capacity in Bi-2223 high-temperature superconductors (HTS). In contrast to the traditional one-step sintering method, a newly developed pressing extension texture enhancement (PETE) method was employed to synthesize high-quality Bi-2223 bulks with larger superconducting phase content of 98.5 % and stronger textural structure of 97.8 %. The improved superconducting quality is beneficial for optimizing carrier concentration, and high critical temperature (Tc∼ 109.4 K) has been obtained. High-resolution transmission electron microscopy (HRTEM) images further reveal the inhibition of amorphous phase and secondary phase particles at grain boundaries, along with enhanced inter-grain connections during the PETE process. The higher inter-grain Jc in 2nd Bi-2223 (Jc,inter∼77.3 A/cm2 at 97 K) compared with 1st Bi-2223 (Jc,inter∼3.68 A/cm2 at 95 K) was found. Moreover, an enhancement in intra-granular pinning force density (Fp) and a transition in the flux pinning mechanism were observed at different temperatures. And the larger intra-grain Jc (Jc, intra ∼107 A/cm2 at 4.2 K,0 T) in 2nd Bi-2223 was obtained. Our work provides a novel technique for preparing high-performance Bi-2223 superconducting bulks, establishing a solid foundation for in-depth study on Bi-2223 superconductors.

Advances in (Cu,C)Ba2Ca3Cu4O11+δ Superconductors with High Critical Transition Temperature and High Irreversibility Magnetic Field

Advances in (Cu,C)Ba2Ca3Cu4O11+δ Superconductors with High Critical Transition Temperature and High Irreversibility Magnetic Field

Thermo-economic assessment and multi-objective optimization of organic Rankine cycle driven by solar energy and waste heat

An organic Rankine cycle (ORC) power generation system driven by integrated solar energy and waste heat is proposed based on the concept of multi-energy complementarity. Three types of solar collectors, two different heat source integration schemes and nine different candidate organic fluids are studied and compared. The effects of main operating parameters on thermo-economic performance are analyzed. A multi-objective optimization framework with a competitive mechanism based multi-objective particle swarm optimizer (CMOPSO) as the core is constructed and the system is optimized. The results of the multi-objective optimization guide the design of the multi-heat source ORC and the selection of the working fluid. When the temperature difference between two heat sources is greater than 50 °C, the heat exchangers are recommended to be connected in series for better overall performance. Besides, the series scheme favors the working fluid with a higher critical temperature, whereas the working fluid with a lower critical temperature is appropriate for the parallel scheme.

Superconductivity in hexagonal Ce$_{0.5}$La$_{0.5}$H$_{9}$ under high pressure

Recently, experimental observation has shown that the substitutional alloy (Ce,La)H$_{9}$ can be successfully synthesized under high pressure, approximately 90-170 GPa and become a superconductor with a high critical temperature ($T\rm_c$)...

Single-Crystal Growth of a Cuprate Superconductor with the Highest Critical Temperature

Millimeter-sized single crystals of a trilayer cuprate superconductor (Hg,Re)Ba2Ca2Cu3O8+d, that exhibits the highest superconducting transition temperature under ambient pressure, were grown reproducibly and safely.

Ab initio study of temperature-dependent piezoelectric and electronic properties of thermally stable GaPO4.

Gallium-phosphate (GaPO4) is one of the ultra-high thermally stable piezoelectric materials with a high critical temperature of 1206 K. Here, first principles calculations with quasi-harmonic approximation are performed to study thermal and other physical properties of α-GaPO4. For the electronic structure, we focus on the electron-phonon interaction and lattice expansion effects on the temperature-dependent band gap, which plays a significant role in zero-point renormalization. Significantly, the large piezoelectric constants e11 primarily comes from intrinsic sensitivity of Ga and O sites to axial strain, while P atoms contribute little, which remains true in other quartz-like type APO4 (A = B, Al, In). Our work provides an insight into the temperature-dependent electronic and piezoelectric properties of α-GaPO4 and motivates its applications in a high temperature environment.

Thermal design and optimization of high-temperature heat pump integrated with district heating benchmarked in Denmark for process heat supply

This work aims to assess and optimize the performance of cascade high-temperature heat pump (HTHP) integrated with district heating (DH) to produce 1 MW steam at 160 °C for the industrial processes. The heat available in the primary loop of the DH network at 80 °C is considered as the heat source; which is cooled down 70 °C through the HTHP evaporator, before supplying the DH secondary loop. The use of alternative hydrocarbons in the low-temperature loop are examined; and considering the gas compressor limitation, the HTHP performance of using each refrigerant is optimized and compared to each other.The optimization results reveal that pentane- hydrocarbon with the highest critical temperature- is the most promising refrigerant to be paired with steam in the high-temperature loop, reaching the highest COP of 2.66. However, concerning safety and compressor sizing issues, butane is an excellent candidate; with volumetric heating capacity (VHC) of about two times more than that of pentane, in the expense of just about 4 % reduction in the HTHP COP. In addition, water injection theoretically controls the steam compressor discharge temperature successfully, with just 0.9 K superheating at the compressor outlet; and reduces its power consumption and the HTHP COP up to 4.3 % and 1.7 %, respectively. Moreover, techno-economic analysis demonstrates that the HTHP technology shows a better business case compared to the conventional natural gas and electric boilers.

Surface treatment of VO2 films with enhancing the modulation of phase transition and thermochromic performance

As a typical phase transition material, vanadium dioxide (VO2) exhibits a promising candidate in the thermochromic field, while the relatively high critical temperature, low luminous transmittance and poor near-infrared modulation impede its practical application. Herein, we propose a facile strategy to overcome the challenges above. The critical temperature of VO2 films gradually reduced as the phosphating temperature increased and became a metallic state even below 2 kelvin. Combining with the first-principles calculations, the mechanism that P-doping induced the metal-insulator transition of VO2 was ascribed to the increment of itinerant electrons, and the migration of the energy band that moved toward the Fermi level. Optical performances demonstrated that the near-infrared modulation ability reached 19.3 %, while there was a 12.1 % improvement in luminous transmittance after the appropriate phosphating process of VO2 films. Meanwhile, the thermal emissivity value greatly decreased from 0.83 to 0.56. The current findings not only offer a novel strategy to boost the thermochromic characteristics of VO2, but also bring insight into a comprehensive understanding of the mechanism of phase transition in VO2.

STUDY OF THE STRUCTURAL AND ELECTRICAL EFFECTS OF THE T2−xAgxBa2Ca2Cu3O10+ SUPERCONDUCTING WITH PARTIAL REPLACEMENT OF SILVER WITH THALLIUM

In this manuscript, the partial substitution of thallium by silver and its effect on the superconducting properties of T2−xAgxBa2Ca2Cu3O10+ is studied with x = 0, 0.15 and 0.25. The samples were prepared by the solid state reaction method. The electrical conductivity was examined using the four probes technique to determine the critical temperature Tc. It was found that increasing the proportions of silver for all produced samples increases the critical temperature. It was also found that the best compensation ratio for x is 0.25, which gives the highest critical temperature, Tc. The ultrastructural properties of the samples were studied using X-ray diffraction. X-ray diffraction study showed that all the prepared samples had a tetragonal structure, with a clear change in the lattice constants. The results also showed that the samples were clearly affected by the replacement of silver with thallium. It was shown that the partial replacement of Tl with Ag promoted the formation of the superconducting 2223 phase

Influence of the Hubbard U Parameter on the Structural, Electronic, Magnetic, and Transport Properties of Cr/Fe/Zr-Based MBenes.

Although relatively new, MBenes are gaining prominence due to their outstanding mechanical, electronic, magnetic, and chemical properties, and they are predicted to be good electrodes for catalytic processes as well as robust 2D magnets with high critical temperatures, to mention some of their intriguing attributes. From all their multiple stoichiometries, a theoretical study of their orthorhombic and hexagonal phases in the framework of density-functional theory is performed in this work. The results suggest that their properties are strongly dependent on the initial conditions considered in the theoretical approach and must be treated with caution. However, and independently of these factors, all of them are demonstrated to be energetically stable, show a metallic behavior, and exhibit, in specific cases, large magnetic moments per unit cell, exceeding 6.5 μB in the case of the orthorhombic-type Cr2B2, making them suitable as robust 2D magnets with room critical temperature. These findings represent an important step toward a better understanding of MBenes, opening several windows to future research in energy conversion and storage, sensing, catalysis, biotechnology, or spintronics.

Layer-dependent electronic and magnetic properties of two-dimensional graphitic molybdenum carbide

Intrinsic magnetic two-dimensional (2D) materials with high critical temperature are highly desired in advanced spintronics applications. Via first-principles calculations, we firstly predict that two-dimensional molybdenum carbide (with a chemical formula of Mo2C12) monolayer is a highly stable antiferromagnetic (AFM) semiconductor with a band gap around 1 eV and a high Néel temperature of 420 K. We then show that the multilayer (Mo2C12)n, where n is the number of layers, exhibits interesting electronic and magnetic properties that are sensitively dependent on the number of layers. The stability of the AFM configuration and the energy gap rapidly decrease with the number of layers. When n≤5, (Mo2C12)n remains AFM, while magnetic moments are mainly located on surface Mo atoms, and Mo atoms on top and bottom surfaces have opposite spin polarizations. When n>5, the AFM phase is unstable and the material becomes metallic. These layer-tunable properties make (Mo2C12)n potentially useful for various electronics and spintronics applications. As one example, an intriguing (Mo2C12)5 based magnetic metal–semiconductor–metal heterojunction is proposed in this work.

THE APPLICATION OF ANALYSIS OF VARIANCE TO DIFFERENT IRON‑BASED SUPERCONDUCTOR CRITICAL TEMPERATURE MODELING

Recently, Iron-based superconductors have shown promising properties of high critical temperature and high upper critical fields, which are prerequisites for applications in highfield magnets. Extensive research has been conducted on a modeling approach that contributes to predicting doped Iron-based superconductor critical temperature from structural and topological parameters. Statistical significance of differences in modeling approaches requires studies that can reliably distinguish between systematic approach effects and errors resulting from modeling approach variation. In this work, we introduce analysis of variance (ANOVA) to assess the statistical significance of differences in modeling approach variation. Comparisons of obtained results with Iron-based modeling approach variation data of support vector machine (SVM) and linear regression with natural logarithm transformation (LRNLT) were presented.

The interplay between exciton- and phonon-induced superconductivity might explain the phenomena observed in LK-99

The experimental results hinting at the room temperature and ambient pressure superconductivity and magnetic levitation in LK-99 attracted an unprecedented interest. While attempts of other teams to reproduce the reported observations on similar samples failed so far, it seems worthwhile to try building a theoretical model that would explain the ensemble of the available data. One of important features that needs to be explained is an apparent contradiction between an extremely high critical temperature Tc and rather modest critical magnetic field Bc and critical current jc reported for LK-99. We show theoretically, that these data may be quantitatively reproduced assuming the interplay between exciton- and phonon-induced superconductivity, while the conventional BCS or Brinkman-Rice-Bardeen-Cooper-Schriefer (BR-BCS) mechanisms would result in a much higher Bc for the same Tc.

Thermo-economic evaluations of novel dual-heater regenerative organic flash cycle (DROFC)

Organic Flash Cycle (OFC) is a promising waste heat utilization technique for low and medium temperature. However, throttling exergy loss in the flash and throttling processes substantially reduces the efficiency of basic organic flash cycle (BOFC). The regenerative organic flash cycle (ROFC) can avoid the exergy loss in the throttling process and enhance the thermodynamic performance of OFC. This paper proposes a novel dual-heater regenerative organic flash cycle (DROFC), which can obtain more power output by reducing the flash process exergy loss and eliminating the mixer exergy loss in ROFC. The thermo-economic performance of DROFC was compared with BOFC and ROFC to evaluate its application potential. Eight low-GWP pure organic fluids were selected and the heat sources were 100–200 °C. Results indicate that DROFC could produce more net power output than BOFC and ROFC with a lower specific investment cost. Specifically, with R600 as an example, the maximum net power output percentage gain of DROFC is 41.19% and 29.09%, respectively. DROFC is more suitable for application scenarios where the heat source temperature exceeds the critical temperature of organic fluid. To balance the net power output and levelized cost of electricity, Hydrocarbons with a high critical temperature are appropriate for DROFC.

Polarons and anharmonicity in high Tc cuprates through vibrational spectroscopies

The discovery in 1986 of superconductivity at high critical temperatures attracted the attention of many researchers not only for its potential applications but also because it represented a theoretical challenge to understanding the mechanism that goes beyond the BCS model. Over 35 years of research, both theoretical and experimental, have not been sufficient to reach a comprehensive description of mechanism governing high Tc superconductivity. We summarize here the experimental signature of polarons and of the anharmonic behavior of the strongly polarizable O−2 ion, two of the possible ingredients of superconductivity in HTc materials, evidenced by Raman and by photoinduced infrared spectroscopy.

Superconductivity and strongly correlated materials in Bariloche

In June 1986, the news on the discovery of high critical temperature superconductivity at IBM, Switzerland, by the physicists Bednorz and Müller, reached the laboratories at the Bariloche Atomic Center in the Argentine Patagonia. The expertise in experimental techniques at low temperatures led by Paco de la Cruz and his team and also in crystal growth led by Daniel Esparza and his group, were important to reproduce the results in a question of a few months. This discovery produced enormous enthusiasm in the community and incentivized research in these materials in other laboratories and theoretical groups at the Bariloche Atomic Center, which had already a vast experience and trajectory in materials science. In this paper I will delve on how this striking discovery fostered theoretical and experimental research in Bariloche which lasts until today.

Superconductivity above 30K Achieved in Dense Scandium

Superconductivity is one of most intriguing quantum phenomena, and the quest for elemental superconductors with high critical temperature (T c) is of great scientific significance due to their relatively simple material composition and the underlying mechanism. Here we report the experimental discovery of densely compressed scandium (Sc) becoming the first elemental superconductor with T c breaking into 30 K range, which is comparable to the T c values of the classic La–Ba–Cu–O or LaFeAsO superconductors. Our results show that of Sc increases from ∼ 3 K at around 43 GPa to ∼ 32 K at about 283 GPa ( K), which is well above liquid neon temperature. Interestingly, measured T c shows no sign of saturation up to the maximum pressure achieved in our experiments, indicating that T c may be even higher upon further compression.