AC loss is a critical consideration in the design of high temperature superconducting (HTS) magnets. REBCO coils exhibit excellent current-carrying capabilities and are popular choices for applications such as fusion magnets and superconducting magnetic energy storage. However, there is currently a lack of research on the AC loss of REBCO coils under low temperature and high field conditions. A quantitative understanding of AC loss over wide temperature and magnetic field ranges is urgently needed. This paper investigates the dynamic resistance, magnetization loss, and total loss of a small double-pancake coil (DPC) based on a 2D axisymmetric H-formulation, at temperatures of 25 K, 50 K, and 77 K in perpendicular AC magnetic fields up to 5 T. The results show that at different temperatures, the dynamic resistance, total loss, and loss components of the DPC can all be scaled by its critical current, I-c,I- coil. This implies that results from the hightemperature, low-field regime can be used to predict the loss values in the low-temperature, high-field regime. In addition, these scaling behaviors are quantitatively explained by the extended equations. This study is expected to provide a valuable reference for the estimation of losses in high-field magnets.

Enhancing the in-field critical current density (J(c)) of YBa2Cu3O7-x (YBCO)-coated conductors is essential for extending their high-field applications. This work investigates the tunability of 2.5 MeV-He-ion irradiation on the performance of YBCO-coated conductors. The results show that, at 10 K and 6.5 T, irradiation with a fluence of 4 & times; 10(14) ions/cm(2) increases J(c) to about 1.8 times that of the pristine sample, while an enhancement factor of approximately 1.6 is still maintained up to 30 K. Structural and performance analyses indicate that irradiation introduces point defects such as oxygen vacancies in the Cu-O planes and induces an expansion of the c-axis lattice. Pinning-force scaling analysis further reveals that the exponent alpha decreases with increasing irradiation fluence, confirming the growing dominance of point-pinning mechanisms, whereas alpha increases systematically with temperature, reflecting a transition toward surface-like pinning behavior. The work demonstrates defect-controlled enhancement of flux pinning for high-field applications.

We report a broadband spectroscopic-ellipsometry study of high-quality (Cu, C)Ba2Ca3Cu4Oy thin films (hereafter abbreviated as (Cu, C)-1234), aimed at tracking the temperature dependence of the electronic structure from 0.5 to 4.2 eV. From the extracted complex dielectric function, we obtain the real optical conductivity sigma 1(omega) and quantify spectral-weight redistribution in four energy windows that separate the low-energy intraband response in contrast to the mid- and high-energy Cu-O interband/charge-transfer excitations. Upon cooling, the spectra display a redistribution of optical spectral weight (SW) that spans more than 1 eV, far larger than the superconducting gap, indicating correlation effects beyond a weak-coupling picture. The low-energy intraband SW is suppressed near a pairing-onset temperature Tconset and partially recovers below the zero-resistance temperature, while weight in Zhang-Rice-singlet and lower Hubbard band-upper Hubbard band charge-transfer channels increases, with the largest high-energy enhancement appearing at or just below Tc0. These observations may indicate a two-stage evolution of the electronic structure, in which precursor pairing or phase fluctuations first reduce the single-particle coherence, followed by further spectral reorganization at lower temperatures. However, considering the relatively broad resistive transition of the film, the observed spectral-weight changes may also be influenced by percolative superconductivity or by a distribution of local transition temperature in the film. This eV-scale spectral-weight redistribution may reflect related electronic or lattice effects discussed in previous studies of cuprates. Our results demonstrate that low- and high-energy electronic degrees of freedom are cooperatively involved in the superconducting transition of multilayer cuprates, thereby motivating layer-resolved spectroscopies and theoretical efforts to clarify the microscopic coupling mechanisms.

This study investigates the effect of BaHfO3 (BHO) addition on the optical properties of YBa2Cu3O7-delta (YBCO) superconducting thin films using spectroscopic ellipsometry. Through Raman spectroscopy and SEM analysis, optimal 10-min Ar ion etching effectively removes surface a-axis-oriented grains and Ba-Cu-O impurities, enhancing surface quality. Optical conductivity analysis reveals a doping-dependent evolution: 10% BHO doping maximizes free carrier density and interband transition efficiency, attributed to optimized Cu-O bond contraction and reduced lattice distortions. Higher doping induces defect clustering, carrier scattering, and redshifted transitions due to lattice expansion. Dielectric function and loss function analyses confirm enhanced plasmonic behavior and flux pinning at 10% doping, while excessive doping degrades electronic transitions. These results highlight the critical role of controlled BHO addition and surface treatment in tailoring the optical and superconducting properties of YBCO, offering insights into the interplay among doping, carrier dynamics, and electronic structure in high-temperature superconductors (HTS).

Superconducting proximity effect and related thickness-driven property evolution remain an important issue in understanding high temperature superconductors. Among proximity systems, superconductor-superconductor (S-S') is special for the existence of intrinsic superconductivity in both materials. Such platform allows the different superconducting orders to compete, couple and reconstruct at the interface. In this paper, (Cu,C)-1234/YBCO heterostructure grown on LAO (001) with fixed thickness of bottom YBCO layer as 150 nm and varied thickness of top (Cu,C)-1234 layer as 188nm, 87 nm, 18nm and estimated 1.2 nm were fabricated and component films were preserved. Electrical transport characterization indicated that as the thickness decrease the (Cu,C)-1234 film degrades and underwent the superconductor-insulator transition (SIT) from thicker to less than 18 nm. In contrast, superconductivity is re-established in transport measurements when the insulating (Cu,C)-1234 layer is coupled to superconducting YBCO As the (Cu,C)-1234 thickness is further reduced to approximately 1.2 nm, the recovered superconductivity is strongly suppressed. The observed thickness dependence is consistent with a scenario in which interfacial coupling restores superconductivity over a finite thickness range before increasing disorder and dimensional confinement dominate in the two-dimensional limit. This work establishes a promising platform for investigating interfacial coupling between cuprate superconductors and provides new insight into the superconducting proximity effect in high-temperature superconducting heterostructures.

Understanding irradiation-induced defect formation in high-temperature superconductors is critical for their application in fusion environments. Here, we use Molecular Dynamics (MD) simulations to study the damage evolution in YBa2Cu3O7-delta (YBCO) under 270 keV proton irradiation. We introduce a depth-resolved analysis framework that accounts for energy deposition and dissipation during proton penetration. Our results show that defects primarily stem from disruptions at Cu and O sites, with defect densities peaking in surface layers for [001] direction collisions. The defect population is found to be highly sensitive to the interatomic potential, as evidenced by the differences between the Gray and Chaplot potentials. In addition, the defect morphology and Frenkel pair distributions are strongly depth-dependent, with severe surface damage gradually diminishing at greater depths. Thermal analysis indicates that displacement cascades cause transient lattice heating, which stabilizes as the cascade evolves. The simulated defect structures (6.34 nm to 10.27 nm) align well with our experimental transmission electron microscopy (TEM) observations (7.8 nm to 12.3 nm). These findings provide atomistic insights into the directional, thermal, and depth-dependent characteristics of radiation damage in YBCO.

This study systematically investigates the effects of 45 MeV and 85 MeV Xe ions irradiation on the in-field performance and defect structures of 3.5 mu m-thick MOD-YBCO superconducting tapes. Transmission electron microscopy (TEM) observations reveal that 85 MeV irradiation produces continuous columnar tracks, while 45 MeV irradiation mainly generates discontinuous tracks. In-field transport measurements show that the critical current of the sample has increased by 2.4 times at 4.2 K and 10 T, from 354 A to 4 mm of the original sample to 874 A-4 mm after 45 MeV irradiation (fluence: 2 & times; 1011 ions/cm2), indicating a significant improvement in the field-dependent critical current density. XRD and Raman analyses further demonstrate that irradiation leads to lattice expansion along the c-axis and the formation of oxygen vacancies, enhancing flux pinning capability. This work confirms that the defect architecture can be effectively optimized by controllably tuning irradiated energy and fluence, thereby substantially improving the high-field current-carrying performance of thick YBCO tapes and providing key experimental evidence for their engineering applications in high magnetic fields.

RE-Ba-Cu-O bulk superconductors can be magnetized to generate high flux density, making them promising for applications such as desktop NMR&MRI, HTS undulators and hybrid magnets assembled with magnets wound by HTS tapes. For these novel concepts, the pinning properties of RE-Ba-Cu-O bulk materials are critical for generating high trapped field and resisting demagnetization especially in cryogenic environments. In the presentation, we are going to report the trapped field of various RE-Ba-Cu-O samples (samples consisting different RE elements and chemical doping) under different temperatures and their lift factor as a macroscopic parameter. The lift factor of trapped field will be compared with that of the HTS tapes to reveal the difference in pinning characteristics between thin film and bulk HTS materials. Best on the achieved understanding, optimization from the material point of view will be proposed.

Hybrid pinning landscape combining one-dimensional (1D) and three-dimensional (3D) defects is regarded as the best solution for enhancing in-field critical current densities Jc of YBCO (YBa2Cu3O7-x). Nevertheless, the interplay between different defects remains unclear. In this work, the effects of hybrid pinning centers containing 3D BaHfO3 nanoparticles (NPs) and irradiation-induced 1D columnar defects (CDs) on YBCO were studied. Irradiation (200 MeV Xe ions, 2e10 ions/cm2) enhanced Jc(77 K, 5 T) by 8.6 times. Interestingly, the temperature dependence of normalized Jc is totally different under different magnetic fields. At low field, the pinning effect of NPs is dominant, while CDs promote vortex creep. Subsequently, contribution of CDs gradually increases with increasing magnetic field, with NPs providing supplemental pinning that suppresses vortex kink expansion between CDs. These findings provide a mechanistic understanding of the dynamic transition within hybrid pinning systems and establish a controllable route for optimizing YBCO performance for large-scale applications.

High-temperature superconductivity in cuprate materials remains a major challenge in physics due to the complexity of their strongly correlated electronic states. Interfacial strain is a powerful lever for tuning electronic correlations in complex oxides, offering new pathways to control emergent quantum phases. Here, we report the discovery of interfacial strain-modulated correlated plasmons observed exclusively in superconducting La1.85Sr0.15CuO4 (LSCO) through spectroscopic ellipsometry. This form of plasmons is absent in the non-superconducting LSCO counterparts. Detailed analysis reveals that these correlated plasmons, arising from the collective excitations within Mott-correlated bands, are driven by long-range electronic correlations in the Cu & horbar;O planes. Furthermore, long-range electronic correlations, intricately modulated by interfacial strain, may play a crucial role in the emergence of superconductivity and in tuning the transition temperature. Dynamical cluster approximation (DCA) with quantum Monte Carlo (QMC) calculations of the extended Hubbard model suggest that long-range Coulomb interactions play an important role in LSCO, showing good agreement with our experimental findings. The collective evidence from both the experimental results and theoretical findings provides new insights into the nature of collective excitations and their pivotal role in the emergence of high-temperature superconductivity.

Demagnetization induced by transverse magnetic fields remains a critical challenge for the practical application of single-grain high-temperature bulk superconductors. In this study, we systematically investigate the dependence of the demagnetization behavior of a GdBa2Cu3Oy (GdBCO) bulk superconductor on the amplitude of the transverse pulsed field, the number of pulses, and the operating temperature. The bulk superconductor was first magnetized by a perpendicular pulsed field, and then a series of transverse pulsed fields with amplitudes ranging from 1 to 2 times the peak trapped field (BT) were applied. The reliable experimental results reveal that the decay of the trapped field increases with the amplitude of the transverse pulsed field and the number of pulses. Significantly, as the operating temperature decreases from 77 K to 70 K, the normalized residual trapped field at the center of the bulk superconductor after ten pulses increases by 20%, 41.2%, and 48.8% for transverse pulsed fields of Ba = BT, 3/2 BT, and 2 BT, respectively. Additionally, as the operating temperature decreases from 70 K to 65 K, the normalized residual trapped field at the center of the bulk superconductor after ten pulses increases by 11.2% and 25.8% for transverse pulsed fields of Ba = BT and 3/2 BT, which can be attributed to the enhanced pinning force at lower temperatures. This study provides an effective strategy for enhancing the dynamic magnetic stability of high-temperature bulk superconductors in various engineering applications.

This study investigates an effective method for preparing high-performance YBa2Cu3O7-δ (YBCO)-coated conductors with thick superconducting layers using a semi-growth strategy on a metal-organic decomposition (MOD) industrial production line. The performance results demonstrate that the semi-growth method offers considerable advantages in terms of the film growth quality and high performance owing to the systematic design of a reserved layer, compared to the performance of 2L+L/2L+2L (semi-growth) YBCO thick tapes of varying thicknesses. The 2L+2L thick films over 3.5 µm achieve a critical current (Ic) of 1150 A/12 mm-width (i.e., 958 A/cm-w) at 77 K@self-field, almost double that of conventional 2L (1.6 µm) YBCO tapes, as well as the in-field performance at low temperature. Although the Ic performance decreases when the film thickness increases to 4.2 µm in 2L+2L mode, the overall trend still demonstrates considerable potential for thick-film fabrication. High-performance YBCO tapes have been successfully scaled to the industrial production of hundreds of meters, showcasing broad application prospects and significant scientific value.

Transistors are the key components in many functional electronics. The performance of n-type field-effect transistors (FETs) based on MoS 2 is limited not only by metal–semiconductor contact performance (e.g. high contact resistance and Schottky barrier height) but also restricted by the interfacial disorders and scattering effects at active channels. In this work, we report a systematic study of lithium fluoride (LiF) used concurrently as a tunneling layer at the metal–MoS 2 interface and a capping layer on the active channel in monolayer MoS 2 FETs. An ultrathin LiF layer ([Formula: see text]2 nm) is thermally deposited before the metal deposition, which behaves as a tunneling layer. In addition, another LiF capping layer ([Formula: see text]10 nm) is deposited on the active channel to mitigate interfacial disorder and screen remote scattering effects, thereby improving intrinsic channel transport. According to the electrical transport characterization, the device shows significant improvement in terms of on-state current ([Formula: see text]83% increase), two-terminal field-effect mobilities ([Formula: see text]40% increase) and on-off ratio ([Formula: see text]2-fold increase) by adopting this proposed strategy. These results elucidate the role of ionic wide-bandgap insulating layers in the synergistic modulation of contacts and channels in two-dimensional semiconductors and provide a simple, generalizable pathway to high-performance, energy-efficient two-dimensional electronics.

We monolithically integrated superconducting nanostrip single-photon detector (SNSPD) and single-flux-quantum (SFQ) circuit on a silicon chip. A 11-nm-thick and 170-nm-wide AlN/NbN meander strip was first defined as the SNSPD on the substrate, followed by the fabrication of SFQ circuits using the 6 kA/cm2 SIMIT Nb03 process. The 2-nm-thick AlN layer was deposited on the NbN to protect it from damage during the subsequent SiO2 layer deposition and etching, and from contamination under ambient exposure. The slight variation of critical current (Ic) and room-temperature resistance (R) of the AlN-coated NbN nanostrip demonstrated enhanced stability in long-term storage. After verifying the functionality and bias current margin of the SFQ circuit using a rectangular wave with amplitude comparable to the SNSPD output signal, we compared the dependence of detection efficiency (DE) on bias current of SNSPD between the SFQ readout circuit and the traditional semiconductor readout circuit. The high degree of consistency between the two methods demonstrates the reliability of this on-chip integration circuit design and fabrication process.

The epitaxial orientation of YBa(2)Cu(3)O(7-delta )grown via the oxygen partial pressure jump pathway in transient liquid-phase assisted chemical solution deposition (TLAG-CSD) depends on the barium-to-copper ratio in the precursor phase. To explore the mechanism behind this phenomenon, in this work we investigate the effects of different oxygen partial pressures and barium-to-copper ratio components on the barium-copper-oxygen liquid phase ([Ba-Cu-O](L)) and the intermediate phase transition in the medium-high temperature heat treatment process. The research shows that the formation of the liquid phase exhibits a point-to-surface characteristic; the temperature and morphological differences in the liquid phase are mainly determined by the composition, with oxygen partial pressure only playing a supporting role. Y & ratio;Ba & ratio;Cu = 0 & ratio;3 & ratio;7 (0-3-7) components all appear before Y & ratio;Ba & ratio;Cu = 0 & ratio;2 & ratio;3 (0-2-3) components in the liquid phase, with a temperature difference of 20 degrees C (high oxygen partial pressure) or 40 degrees C (low oxygen partial pressure). Experimental results indicate that there are differences in the intermediate phase properties between these two components. Under high oxygen partial pressure, the intermediate phase BaCuO2 exhibits a single characteristic peak in the 0-3-7 component, with large and dispersed grains; the 0-2-3 component has multiple characteristic peaks, with small and dense grains. The surface area of the liquid phase region in the 0-3-7 component is smaller than that in the 0-2-3 component, resulting in different supersaturation levels of Y3+ in the liquid phases of the two components and causing orientation differences in YBCO. Finally, the basic model for the formation of fluorine-free liquid phase is summarized, and the complete [Ba-Cu-O](L) film can be generated from the 0-2-3 component at high oxygen partial pressure and 750 degrees C.

Understanding the electronic properties of doped copper-oxygen planes remains a significant challenge in condensed matter physics and is crucial to unraveling the mechanisms behind high-temperature superconductivity in cuprates. Recently, the observation of charge transfer and interfacial polarons in a superconducting interface has aroused extensive research interest. However, experimental data to investigate charge transfer on the CuO2 plane and the presence of polarons are still missing. Here we conduct extensive research on the optical and electronic properties of 2D materials supported on copper-based superconductors. Unlike monolayer-WSe2 on other substrates, monolayer-WSe2 on La1.85Sr0.15CuO4 (WSe2/LSCO) produces a special band structure. Using high-resolution spectroscopic ellipsometry and density functional theory calculation methods, the special electronic structure can be attributed to the formation of the interfacial small polaron at the WSe2/LSCO interface which is driven by charge transfer between the CuO2 plane of the cuprate superconductor and WSe2. In addition, the structural phase transition of the LSCO substrate was observed to reduce the e-h interaction of WSe2. These findings may spur future investigations on the effect of the interfacial polaron on the superconductivity of cuprates and highlight the significant influence of interface effects on the electronic structure of WSe2 films. It provides an effective method to further explore the intrinsic relationship between interfacial polarons and superconductivity.

Medium and high entropy alloys (MEAs and HEAs) have emerged as promising materials in materials science and engineering, offering exceptional mechanical properties and intriguing low-temperature physical characteristics. In the study of superconducting mechanisms, high-quality, large single crystals are essential for obtaining reliable experimental data. Here, we report the first successful growth of high-quality MEA HfNbZrTi single crystals using the Floating Zone Method and present a comprehensive investigation of their superconducting properties, vortex dynamics, and specific heat. Notably, the specific heat jump extracted from experimental data yields Delta C/gamma T-c = 1.43, while the superconducting gap Delta(0) is 0.92 meV, precisely matching the theoretical prediction of the weak-coupling Bardeen-Cooper-Schrieffer model. Furthermore, we report the first investigation of magnetic relaxation in MEA single crystals, revealing an exceptionally low relaxation rate (S < 0.02 at 2 K). These findings not only provide strong experimental evidence supporting the application of MEAs and HEAs superconductors but also open new avenues for the development of superconductors with ultralow magnetic relaxation rates.

Cuprate superconductors remain central to condensed matter physics due to their technological relevance and unconventional, incompletely understood electronic behavior. While the canonical phase diagram and low-energy models have been shaped largely by studies of underdoped and moderately doped cuprates, the overdoped regime has received comparatively limited attention.Here, we track the evolution of the electronic structure from optimal to heavy overdoping in La2-xSrxCuO4(LSCO) using broadband optical spectroscopy across x=0.15-0.60. The measured spectral changes–including the redistribution of Zhang-Rice-related spectral weigh–are in qualitative agreement with determinant quantum Monte Carlo simulations of the three-orbital Emery model, which together indicate a pronounced reconstruction of the electronic structure beyond hole concentrations x>0.2. Guided by these observations, we propose a spontaneous checkerboard-type Zhang-Rice electronic configuration that captures the coexistence of itinerant and localized carriers characteristic of the heavily overdoped state. Our results refine the doping-dependent Zhang-Rice-based framework for cuprates, illuminate how correlations persist deep into the overdoped regime, and provide new constraints on microscopic mechanisms of high-temperature superconductivity, with broader implications for correlated transition-metal oxides.