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In a classic paper of 1960, W. H. Cherry and J. I. Gittleman discussed various thermal and electrodynamic aspects of the superconductive transition process relevant to practical applications. In a section of the paper that has remained unnoticed, they proposed a physical model for the Meissner effect. Earlier in 1940–1943, in work that has also remained unnoticed, K. M. Koch had introduced related physical ideas to explain the Meissner effect. Still earlier in 1937, J. C. Slater proposed a model to explain the perfect diamagnetism of superconductors. None of these ideas are part of the conventional London-BCS understanding of superconductivity, yet I will argue that they are essential to understand the Meissner effect, the most fundamental property of superconductors. The unconventional theory of hole superconductivity unifies and extends these ideas. A key missing element in the conventional theory as well as in these early theories is electron-hole asymmetry. A proper understanding of the Meissner effect may help with practical applications of superconductors, as well as to find new superconducting materials with desirable properties. [ABSTRACT FROM AUTHOR]

In this paper we address the question of whether high-temperature superconductors have anything in common with BCS-BEC crossover theory. Towards this goal, we present a proposal and related predictions which provide a concrete test for the applicability of this theoretical framework. These predictions characterize the behavior of the Ginzburg-Landau coherence length, ξ 0 coh , near the transition temperature Tc, and across the entire superconducting Tc dome in the phase diagram. That we are lacking a systematic characterization of ξ 0 coh in the entire class of cuprate superconductors is perhaps surprising, as it is one of the most fundamental properties of any superconductor. This paper is written to motivate further experiments and, thus, address this shortcoming. Here we show how measurements of ξ 0 coh contain direct indications for whether or not the cuprates are associated with BCS-BEC crossover and, if so, where within the crossover spectrum a particular superconductor lies. [ABSTRACT FROM AUTHOR]

In this study, the prediction of n-value (index-value) surfaces—a key indicator of the field and temperature dependence of critical current density in superconductors—across various high-temperature superconducting materials is addressed using a deep learning modeling approach. As superconductors play a crucial role in advanced technological applications in aerospace and fusion energy sectors, improving their performance model is essential for both practical and academic research purposes. The feed-forward deep learning network technique is employed for the predictive modeling of n-value surfaces, utilizing a comprehensive dataset that includes experimental data on material properties and operational conditions affecting superconductors' behavior. The model demonstrates enhanced accuracy in predicting n-value surfaces when compared to traditional regression methods by a 99.62% goodness of fit to the experimental data for unseen data points. In this paper, we have demonstrated both the interpolation and extrapolation capabilities of our proposed DFFNN technique. This research advances intelligent modeling in the field of superconductivity and provides a foundation for further exploration into deep learning predictive models for different superconducting devices. [ABSTRACT FROM AUTHOR]

There is a wide variety of superconducting materials, but only a few of them are suitable for practical industrial use, and one of the most promising superconductors is MgB2. Its main advantages are a critical temperature close to 40 K, which allows for operation in a cryogenic environment, low cost of precursors, and the ease of manufacture. In this paper, we attempted to obtain superconducting materials based on magnesium diboride in a new way by using a high-temperature centrifuge and then investigated how centrifugal acceleration could affect the superconducting characteristics of the materials in a greater way during combustion synthesis. As a brief result of this research, it was found that the value of centrifugal acceleration affected the critical current density (Jc = 1.4 A/cm2) of the MgB2 composites, although it did not considerably impact the critical transition temperature of the MgB2 materials (remained at around 37.5–38 K). [ABSTRACT FROM AUTHOR]

This paper analyzes the viability of different solutions to passively augment the axial stiffness of a horizontal axis radial levitation passive magnetic bearing (PMB) with a previously studied topology. The zero-field cooling (ZFC) of high-temperature superconductor (HTS) bulks promotes higher magnetic impulsion and levitation forces and lower electromagnetic losses than those with field-cooling (FC) but, on the other hand, the guiding stability is much lower than those with FC. Because of stability reasons, FC was adopted in most superconducting maglev systems. The trend of this research group has been to develop a horizontal axis HTS ZFC radial levitation PMB presenting notable levitation forces with reduced electromagnetic losses, defined by a topology that creates guiding stability. Previous work has shown that optimizing the bearing geometry to maximize magnetic guidance forces might not be enough to guarantee the axial stiffness required for many applications. First, the extent to which guidance forces are augmented by increasing the number of HTS bulks in the stator is evaluated. Then, the axial stiffness augmentation by passively adding two limiting permanent magnet (PM) rings is evaluated. The results show that the axial stiffness is highly augmented by adding limiting PM rings with no significant additional investment. This change enables the use of the studied ZFC superconducting PMB in high-precision axial stability applications, such as precision gyroscopes, horizontal axis propellers, and turbines. [ABSTRACT FROM AUTHOR]

This paper concerns static and evolution equations involving degenerate curls. The topic is motivated by the mathematical problems of Meissner states of anisotropic superconductors, and of the nonlinear magneto-static Maxwell equations with strong anisotropy. Two types of degenerate curls are studied, among them one is the directional curl along a unit length vector field, which has been introduced by the author before, and the other is the matrix-curl, which is introduced in this paper. Because of the degeneracy produced by the degenerate curl of the unknown vector field in the leading term of the equation, the boundary condition should be prescribed on part of the boundary according to the nature of the degenerate curl. We formulate the Dirichelt type and natural type boundary conditions, and give existence of solutions both for the static equations and for the evolution equations. [ABSTRACT FROM AUTHOR]

Kagome superconductors AV3Sb5 (A = K, Rb, and Cs) have attracted enormous interest due to the coexistence of charge density wave (CDW) order, unconventional superconductivity (SC) and anomalous Hall effect (AHE). In this paper, we reported an intensive investigation on Cs(V1−xTax)3Sb5 single crystals with systematic Ta doping. Ta was confirmed to be doped into V-site in the Kagome layer from both single crystal X-ray diffraction structural refinement and scanning transmission electron microscopy observation. The highest Ta doping level was found to be about 16%, which is more than twice as much as 7% in Nb-doped CsV3Sb5. With the increase of Ta doping, CDW order was gradually suppressed and finally vanished when the doping level reached to more than 8%. Meanwhile, superconductivity was enhanced with a maximum critical temperature (Tc) of 5.3 K, which is the highest Tc in the bulk crystal of this Kagome system at ambient pressure so far. The μ0Hc2(T) behavior demonstrates that the system is still a two-band superconductor after Ta doping. Based on the electrical transport measurement, a phase diagram was set up to exhibit the evolution of CDW and SC in the Cs(V1−xTax)3Sb5 system. These findings pave a new way to search for new superconductors with higher Tc in the AV3Sb5 family and establish a new platform for tuning and controlling the multiple orders and superconducting states. [ABSTRACT FROM AUTHOR]

In this paper, the properties of higher dimensional holographic superconductors are studied in the background of f(R) gravity and Born–Infeld electrodynamics. A specific model of f(R) gravity is considered, allowing a perturbative approach to the problem. The Sturm–Liouville eigenvalue problem is used to analytically calculate the critical temperature and the condensation operator. An expression for the critical temperature in terms of the charge density including the correction from modified gravity is derived. It is seen that the higher values of the Born–Infeld coupling parameter make the condensation harder to form. In addition, the limiting values of this parameter, above which Born–Infeld electrodynamics cannot be applied, are found for different dimensions. Another interesting property is that the increasing modifications of f(R) gravity lead to larger values of the critical temperature and a decrease in the condensation gap, which means that the condensation is easier to form. [ABSTRACT FROM AUTHOR]

Kagome superconductors AV3Sb5 (A = K, Rb, and Cs) have attracted enormous interest due to the coexistence of charge density wave (CDW) order, unconventional superconductivity (SC) and anomalous Hall effect (AHE). In this paper, we reported an intensive investigation on Cs(V1−xTax)3Sb5 single crystals with systematic Ta doping. Ta was confirmed to be doped into V-site in the Kagome layer from both single crystal X-ray diffraction structural refinement and scanning transmission electron microscopy observation. The highest Ta doping level was found to be about 16%, which is more than twice as much as 7% in Nb-doped CsV3Sb5. With the increase of Ta doping, CDW order was gradually suppressed and finally vanished when the doping level reached to more than 8%. Meanwhile, superconductivity was enhanced with a maximum critical temperature (Tc) of 5.3 K, which is the highest Tc in the bulk crystal of this Kagome system at ambient pressure so far. The μ0Hc2(T) behavior demonstrates that the system is still a two-band superconductor after Ta doping. Based on the electrical transport measurement, a phase diagram was set up to exhibit the evolution of CDW and SC in the Cs(V1−xTax)3Sb5 system. These findings pave a new way to search for new superconductors with higher Tc in the AV3Sb5 family and establish a new platform for tuning and controlling the multiple orders and superconducting states. [ABSTRACT FROM AUTHOR]

• For superconductor REBa 2 Cu 3 O 7-x (REBCO, RE = rare earth) tapes. • A randomly distributed multi-edge crack model was established based on the H -formulation and the J-integral method. • The interaction effect of multiple edge cracks was investigated by the comparison of various edge crack models. • Numerical results indicate that geometrical parameter randomness is essential for the fracture damage of REBCO tapes. It is often necessary to narrow wide tapes through a slitting process in applications of the second-generation high-temperature superconductor REBa 2 Cu 3 O 7-x (REBCO, RE = rare earth) tapes. However, this results in some random length edge cracks appearing on the slit edge and extending at certain angles towards the center of the tape. In this paper, we proposed a randomly distributed multiple-edge crack model to investigate the fracture mechanism of the superconducting tape under electromagnetic force due to high magnetic fields and current density (∼10 T and ∼ 1010A/m2). The electromagnetic body force distributions within the superconducting tape, incorporating multiple edge cracks, are simulated based on the H-formulation. Then a fracture analysis is conducted under the combined loading of tensile and electromagnetic forces, with the numerical calculation of stress intensity factors (SIFs) using the J-integral method. To validate the model's accuracy, we compare the body force distribution caused by an edge crack and the SIFs of edge cracks under uniform tension with existing results. Detailed analyses are undertaken to explore the impacts of electromagnetic body force non-uniformity, interactions between neighboring cracks, and the stochastic nature of geometrical parameters (length, angle, and spacing) on the fracture behavior under an alternating magnetic field. Numerical results indicate that non-uniform electromagnetic body forces arising from defects are a critical factor in crack propagation. Furthermore, the randomness of the geometrical parameters amplifies the interactions between some of the neighboring cracks, causing the tendency of the tape containing random edge cracks to fracture. Therefore, it is advisable to avoid random cracks with substantial length, angle, and spacing during the mechanical slitting process. [ABSTRACT FROM AUTHOR]

This paper serves as a primer on superconductivity, inviting students for further investigation. Although the theory of superconductivity is a many-body quantum theory, here we take a more didactic route based on thermodynamics and symmetry. We briefly survey the more than a century-old field and provide a one-sentence definition of a superconductor. Surprisingly, many textbooks lack such a definition, usually introducing superconductors through their properties rather than by definition. We explain the concept of an order parameter, symmetry, and symmetry breaking. Based on this, we clarify the difference between conventional and unconventional superconductors, which is frequently a confusing topic for newcomers. We provide the reader with a taste of a current research topic in the field of unconventional superconductivity and magnetism. For this, we explain the concept of time-reversal symmetry breaking in condensed matter physics, which is usually associated with a form of magnetism. Here, we show that time-reversal symmetry might be broken in superconductors, leading to magnetic properties due to superconductivity itself. For this purpose, we utilize the method of the Ginzburg-Landau theory for phase transitions. We discuss the field of chiral superconductivity and guide the interested reader to further study. [ABSTRACT FROM AUTHOR]

Majorana zero modes have gained significant interest due to their potential applications in topological quantum computing and in the realization of exotic quantum phases. These zero-energy quasiparticle excitations localize at the vortex cores of two-dimensional topological superconductors or at the ends of one-dimensional topological superconductors. Here we describe an alternative platform: a two-dimensional topological superconductor with inhomogeneous superconductivity, where Majorana modes localize at the ends of topologically nontrivial one-dimensional stripes induced by the spatial variations of the order parameter phase. In certain regimes, these Majorana modes hybridize into a single highly nonlocal state delocalized over spatially separated points, with exactly zero energy at finite system sizes and with emergent quantum-mechanical supersymmetry. We then present detailed descriptions of braiding and fusion protocols and showcase the versatility of our proposal by suggesting possible setups that can potentially lead to the realization of Yang-Lee anyons and the Sachdev-Ye-Kitaev model. [ABSTRACT FROM AUTHOR]

Pressurized hydrogen-based superconductors are phonon-mediated superconductors that exhibit high phonon frequencies. In these superconductors, in addition to the density of states (DOS) at the Fermi energy ( E F ), the energy dependence of the DOS around E F becomes important for evaluating their transition temperature ( T c ). Systems with peak structures in the DOS around E F , such as I m 3 ¯ m H 3 S and F m 3 ¯ m LaH 10 , highlight this point. We use the fully ab initio Eliashberg method to investigate this phenomenon in I m 3 ¯ m CaH 6 and F m 3 ¯ m ThH 10 with a dip structure in their DOS around E F . Our calculated T c values (225–235 K for CaH 6 at 200 GPa and 156–158 K for ThH 10 at 170 GPa) are quantitatively consistent with the experimental results. Remarkably, our results from the self-consistent treatment of the electron Green's function contrasts with those cases with a peak structure in the DOS. This finding unifies the understanding of how DOS structures influence the evaluation of T c . [ABSTRACT FROM AUTHOR]

High temperature superconductors (HTSs) are enablers of extensive electrification for aircraft propulsion. Indeed, if used in electrical machines, HTS materials can drastically improve their performance in terms of the power-to-weight ratio. Among the different topologies of superconducting electrical machines, a flux modulation machine based on HTS bulks is of interest for its compactness and light weight. Such a machine is proposed in the FROST (Flux-barrier Rotating Superconducting Topology) project led by Airbus to develop new technologies as part of their decarbonization goals driven by international policies. The rotor of the machine will house large ring-segment-shaped HTS bulks in order to increase the output power. However, the properties of those bulks are scarcely known and have barely been investigated in the literature. In this context, the present work aims to fill out partially this scarcity within the framework of FROST. Thus, a thorough characterisation of the performances and homogeneity of 11 large REBaCuO bulks was carried out. Ten of the bulks are to be utilized in the machine prototype, originally keeping the eleventh bulk as a spare. A first set of characterisation was conducted on the eleven bulks. For this set, the trapped field mapping and the critical current were estimated. Then, a series of in-depth characterisations on the eleventh bulk followed. It included critical current measurement, X-ray diffraction, and scanning electron microscopy on different millimetre-size samples cut out from the bulk at various locations. The X-ray diffraction and scanning electron microscopy showed weakly oxygenated regions inside the bulk explaining the local drop or loss in superconducting properties. The objective was to determine the causes of the inhomogeneities found in the trapped field measured on all the bulks, sacrificing one of them, here the spare one. To help obtain a clearer picture, a numerical model was then elaborated to reproduce the field map of the eleventh bulk using the experimental data obtained from the characterisation of its various small samples. It is concluded that further characterisations, including the statistics on various bulks, are still needed to understand the underlying reasons for inhomogeneity in the trapped field. Nonetheless, all the bulks presented enough current density to be usable in the construction of the proposed machine. [ABSTRACT FROM AUTHOR]

In this letter, we report our observation of an extraordinarily rich phase diagram of a LaScO3/SrTiO3 heterostructure. Close to the superconducting transition temperature, the system hosts a superconducting critical point of the Infinite-randomness type characterized by an effective dynamical exponent ν z that diverges logarithmically. At lower temperatures, we find the emergence of a magnetic field-tuned metallic phase that co-exists with a quantum Griffiths phase (QGP). Our study reveals a previously unobserved phenomenon in 2D superconductors—an unanticipated suppression of the QGP below a crossover temperature in this system. This concealment is accompanied by the destruction of the superconducting quantum critical point (QCP) signaled by a power-law divergence (in temperature) of the effective dynamical exponent. These observations are entirely at odds with the predictions of the infinite-randomness scenario and challenge the very concept of a vanishing energy scale associated with a QCP. We develop and discuss possible scenarios like smearing of the phase transition that could plausibly explain our observations. Our findings challenge the notion that QGP is the ultimate ground state in two-dimensional superconductors. [ABSTRACT FROM AUTHOR]

The kink structure in band dispersion usually refers to a certain electron-boson interaction, which is crucial in understanding the pairing in unconventional superconductors. Here we report the evidence of the observation of a kink structure in Fe-based superconductor CsCa2Fe4As4F2 using angle-resolved photoemission spectroscopy. The kink shows an orbital selective and momentum dependent behavior, which is located at 15 meV below Fermi level along the Γ − M direction at the band with dxz orbital character and vanishes when approaching the Γ − X direction, correlated with a slight decrease of the superconducting gap. Most importantly, this kink structure disappears when the superconducting gap closes, indicating that the corresponding bosonic mode (~ 9 ± 1 meV) is closely related to superconductivity. However, the origin of this mode remains unidentified, since it cannot be related to phonons or the spin resonance mode (~15 meV) observed by inelastic neutron scattering. The behavior of this mode is rather unique and challenges our present understanding of the superconducting paring mechanism of the bilayer FeAs-based superconductors. The kink structure in the band dispersion can be linked to electron-boson interaction and has been reported in unconventional superconductors. Here the authors observe an orbital selective and momentum dependent kink feature in an Fe-based superconductor, which is highly correlated with superconductivity. [ABSTRACT FROM AUTHOR]

Searching for topological superconductors that host topological charge-neutral Majorana zero-modes at edges has become a central problem in condensed matter research due to their potential applications for quantum computations. Meanwhile, electron correlations in solid-state materials enhance quantum fluctuations and give rise to various quantum many-body phases. Whether these electron correlations alone would lead to topological superconductivity is a fundamentally important open problem. Here, we theoretically find the correlation-driven topological superconductivity in a class of Kondo lattice materials. Therein, the odd-parity Kondo hybridization mediates ferromagnetic spin-spin coupling and leads to spin-triplet pairing between local moments. Triplet p ± i p ′ -wave topological superconductivity with Majorana zero modes at edges is reached when Kondo hybridization co-exists with the triplet pairings. Our results offer a detailed understanding of the experimental observations on UTe2, a ferromagnetic heavy-electron triplet superconductor. Our approach to topological superconductivity shows advantages over the heterostructure approach by proximity effect. The authors find theoretically topological superconductivity in a class of Kondo lattice materials driven by strongly correlated Kondo effects with odd-parity Kondo hybridization. Their results offer a detailed understanding of UTe2, a ferromagnetic heavy-electron triplet superconductor, as well as a guiding principle in the search for topological superconductors. [ABSTRACT FROM AUTHOR]

The interaction between lattice vibrations and electrons plays a key role in various aspects of condensed matter physics — including electron hydrodynamics, strange metal behavior, and high-temperature superconductivity. In this study, we present systematic investigations using Raman scattering and angle-resolved photoemission spectroscopy (ARPES) to examine the phononic and electronic subsystems of the topological superconductor candidate 2M-WS2. Raman scattering exhibits an anomalous nonmonotonic temperature dependence of phonon linewidths, indicative of strong phonon–electron scattering over phonon–phonon scattering. The ARPES results demonstrate pronounced dispersion anomalies (kinks) at multiple binding energies within both bulk and topological surface states, indicating a robust and mode-selective coupling between the electronic states and various phonon modes. These experimental findings align with previous calculations of the Eliashberg function, providing a deeper understanding of the highest superconducting transition temperature observed in 2M-WS2 (8.8 K) among all transition metal dichalcogenides as induced by electron–phonon coupling. Furthermore, our results may offer valuable insights into other properties of 2M-WS2 and guide the search for high-temperature topological superconductors. Electron–phonon coupling is a key physical process in condensed matter systems that plays a crucial role in phenomena such as superconductivity. Here, the authors characterize the role of electron–phonon coupling in the topological superconductor candidate 2M-WS2, indicating a robust and mode-selective coupling that informs the nature of its relatively high superconducting transition temperature. [ABSTRACT FROM AUTHOR]

The pairing symmetry of Sr2RuO4 is a long-standing fundamental question in the physics of superconducting materials with strong electronic correlations. We use the functional renormalization group to investigate the behavior of superconductivity under uniaxial strain in a two-dimensional realistic model of Sr2RuO4 obtained with density functional theory and incorporating the effect of spin-orbit coupling. We find a dominant d x 2 − y 2 superconductor mostly hosted by the dxy-orbital, with no other closely competing superconducting state. Within this framework, we reproduce the experimentally observed enhancement of the critical temperature under strain and propose a simple mechanism driven by the density of states to explain our findings. We also investigate the competition between superconductivity and spin-density wave ordering as a function of interaction strength. By comparing theory and experiment, we discuss constraints on a possible degenerate partner of the d x 2 − y 2 superconducting state. [ABSTRACT FROM AUTHOR]

Superconductivity of iron chalocogenides is strongly enhanced under applied pressure yet its underlying pairing mechanism remains elusive. Here, we present a quantum oscillations study up to 45 T in the high-Tc phase of tetragonal FeSe0.82S0.18 up to 22 kbar. Under applied pressure, the quasi-two-dimensional multi-band Fermi surface expands and the effective masses remain large, whereas the superconductivity displays a threefold enhancement. Comparing with chemical pressure tuning of FeSe1−xSx, the Fermi surface expands in a similar manner but the effective masses and Tc are suppressed. These differences may be attributed to the changes in the density of states influenced by the chalcogen height, which could promote stronger spin fluctuations pairing under pressure. Furthermore, our study also reveals unusual scattering and broadening of superconducting transitions in the high-pressure phase, indicating the presence of a complex pairing mechanism. [ABSTRACT FROM AUTHOR]

Contrary to the current consensus, I argue that the existing evidence for high-temperature superconductivity in hydrides under high pressure is not compelling. I suggest that the focus of the field should urgently shift to establish unequivocally experimentally whether or not superconductivity in pressurized hydrides exists, instead of continuing to search for new materials that might show elusive signals of unproven superconductivity at ever higher temperatures. The implications of a negative finding for the theoretical understanding of superconductivity are discussed. [ABSTRACT FROM AUTHOR]

This work reports the formation of a heterojunction composed of Tl2Ba2CaCu2O8 (Tl‐2212) and Bi2Se3 as the high critical temperature superconductor and topological insulator, respectively. The Bi2Se3 film is deposited on the Tl‐2212 by a chemical mechanical polishing process. Due to the rough surface of Tl‐2212, the treated Tl‐2212 is then subjected to post‐annealing at various temperatures. This temperature does not affect the formation of the interfacial layer at the heterojunction; however, an improved layered crystal structure of the Bi2Se3 film is observed at 500 °C. The in‐depth profile of the relative atomic concentration indicates the diffusion of Cu and Tl into the Bi2Se3 film with the Ba diffusion being closer to the interfacial layer. At 500 °C, Cu atoms are more actively diffused into the Bi2Se3 film, thus blocking Tl diffusion, and improving the layered crystal structure of the film. The density functional theory calculations reveal that the lowest formation energy of the Cu vacancy is when Bi2Se3 is in contact with Tl‐2212, which results in the diffusion of Cu atoms from Tl‐2212, thus transforming the interstitial Cu atoms into the film. These atoms have an n‐type doping effect and prefer intercalating at a vdW gap deep inside the layered Bi2Se3. [ABSTRACT FROM AUTHOR]

Considerable evidence shows that the heavy fermion material UTe2 is a spin-triplet superconductor, possibly manifesting time-reversal symmetry breaking, as measured by Kerr effect below the critical temperature, in some samples. Such signals can arise due to a chiral orbital state or possible nonunitary pairing. Although experiments at low temperatures appear to be consistent with point nodes in the spectral gap, the detailed form of the order parameter and even the nodal positions are not yet determined. Thermal conductivity measurements can extend to quite low temperatures, and varying the heat current direction should be able to provide information on the order parameter structure. Here, we derive a general expression for the thermal conductivity of a spin-triplet superconductor and use it to compare the low-temperature behavior of various states proposed for UTe2. [ABSTRACT FROM AUTHOR]

The mechanism of high-temperature superconductivity in copper oxides (cuprate) remains elusive, with the pseudogap phase considered a potential factor. Recent attention has focused on a long-range symmetry-broken charge-density wave (CDW) order in the underdoped regime, induced by strong magnetic fields. Here by 63,65Cu-nuclear magnetic resonance, we report the discovery of a long-range CDW order in the optimally doped Bi2Sr2−xLaxCuO6 superconductor, induced by in-plane strain exceeding ∣ε∣ = 0.15 %, which deliberately breaks the crystal symmetry of the CuO2 plane. We find that compressive/tensile strains reduce superconductivity but enhance CDW, leaving superconductivity to coexist with CDW. The findings show that a long-range CDW order is an underlying hidden order in the pseudogap state, not limited to the underdoped regime, becoming apparent under strain. Our result sheds light on the intertwining of various orders in the cuprates. The authors study the optimally-doped cuprate superconductor Bi2Sr2−xLaxCuO6 by nuclear magnetic resonance. They find a long-range charge density wave (CDW) order induced by uniaxial strain, showing that CDW order is a hidden order of the pseudogap state, not limited to the underdoped regime. [ABSTRACT FROM AUTHOR]

The kagome lattice is an intriguing and rich platform for discovering, tuning and understanding the diverse phases of quantum matter, crucial for advancing modern and future electronics. Despite considerable efforts, accessing correlated phases at room temperature has been challenging. Using single-crystal X-ray diffraction, we discovered charge order above room temperature in La(Ru1−xFex)3Si2 (x = 0, 0.01, 0.05), where charge order related to out-of-plane Ru atom displacements appears below TCO,I ≃ 400 K. The secondary charge ordered phase emerges below TCO,II ≃ 80–170 K. Furthermore, first principles calculations reveal both the kagome flat band and the van Hove point near the Fermi energy in LaRu3Si2, driven by Ru-dz2 orbitals. Our results identify LaRu3Si2 as the kagome superconductor with the highest known charge ordering temperature, offering a promising avenue for researching room temperature quantum phases and developing related technologies. The study focuses on the charge order in LaRu3Si2, a material with a kagome lattice structure, discovering a charge-ordered state that persists at or above room temperature. This finding classifies LaRu3Si2 as the kagome superconductor with the highest charge ordering temperature, suggesting potential for applications in devices operating at normal environmental conditions without the need for cooling. [ABSTRACT FROM AUTHOR]

Iron-based high-temperature (high-Tc) superconductors have good potential to serve as materials in next-generation superstrength quasipermanent magnets owing to their distinctive topological and superconducting properties. However, their unconventional high-Tc superconductivity paradoxically associates with anisotropic pairing and short coherence lengths, causing challenges by inhibiting supercurrent transport at grain boundaries in polycrystalline materials. In this study, we employ machine learning to manipulate intricate polycrystalline microstructures through a process design that integrates researcher- and data-driven approaches via tailored software. Our approach results in a bulk Ba0.6K0.4Fe2As2 permanent magnet with a magnetic field that is 2.7 times stronger than that previously reported. Additionally, we demonstrate magnetic field stability exceeding 0.1 ppm/h for a practical 1.5 T permanent magnet, which is a vital aspect of medical magnetic resonance imaging. Nanostructural analysis reveals contrasting outcomes from data- and researcher-driven processes, showing that high-density defects and bipolarized grain boundary spacing distributions are primary contributors to the magnet's exceptional strength and stability. Breakthrough in Superconducting Magnet Strength and Stability: Iron-based superconductors are promising for uses like quantum computing and superstrong magnets. However, improving their superconducting properties is challenging. This study aimed to improve these properties in a specific superconductor, K-doped Ba122, using Bayesian optimization. The researchers made samples under different conditions and measured their superconducting properties to refine the process. Two large disk-shaped samples were made using the best processing conditions found from data-driven and researcher-driven methods. The superconducting properties of these samples, and their ability to act as magnets, were tested at low temperatures. The results showed significant improvements, proving the optimization process's effectiveness and resulting in an iron-based superconducting magnet with unprecedented strength. The study concludes that machine learning, especially Bayesian optimization, can significantly advance high-performance superconducting materials development. This could lead to more efficient and powerful superconducting magnets for various uses. This summary was initially drafted using artificial intelligence, then revised and fact-checked by the authors. The world's strongest iron-based superconducting magnet has been manufactured. Machine learning using Bayesian optimization was employed to improve the superconducting properties of potassium-doped barium iron arsenide (Ba,K)Fe2As2. Two large disk-shaped samples were fabricated using common industrial processing techniques under the best conditions deduced from data- and researcher-driven methods. After magnetizing the samples, they could retain a magnetic field of 2.83 T as a quasi-permanent magnet, around 2.7 times the previous record, with decay rates less than −0.1 ppm/h, crucial for MRI scanners. The two approaches produced divergent microstructures, opening the door to redefining what makes for a superior superconducting material. [ABSTRACT FROM AUTHOR]

Vortices in superconductors can help identify emergent phenomena but certain fundamental aspects of vortices, such as their entropy, remain poorly understood. Here, we study the vortex entropy in underdoped Bi2Sr2CaCu2O8+x by measuring both magneto-resistivity and Nernst effect on ultrathin flakes (≤2 unit-cell). We extract the London penetration depth from the magneto-transport measurements on samples with different doping levels. It reveals that the superfluid phase stiffness ρs scales linearly with the superconducting transition temperature Tc, down to the extremely underdoped case. On the same batch of ultrathin flakes, we measure the Nernst effect via on-chip thermometry. Together, we obtain the vortex entropy and find that it decays exponentially with Tc or ρs. We further analyze the Nernst signal above Tc in the framework of Gaussian superconducting fluctuations. The combination of electrical and thermoelectric measurements in the two-dimensional limit provides fresh insight into high temperature superconductivity. The authors study the vortex entropy in ultrathin flakes of the underdoped cuprate superconductor Bi2Sr2CaCu2O8+x by measuring both magneto-resistivity and Nernst effect. They find that, while the superfluid phase stiffness varies linearly with Tc, the vortex entropy decreases exponentially at lower Tc. [ABSTRACT FROM AUTHOR]

A growing number of superconducting materials display evidence for spontaneous time-reversal symmetry breaking (TRSB) below their critical transition temperatures. Precisely what this implies for the nature of the superconducting ground state of such materials, however, is often not straightforward to infer. We review the experimental status and survey different theoretical mechanisms for the generation of TRSB in superconductors. In cases where a TRSB complex combination of two superconducting order parameter components is realized, defects, dislocations and sample edges may generate superflow patterns that can be picked up by magnetic probes. However, even single-component condensates that do not break time-reversal symmetry in their pure bulk phases can also support signatures of magnetism inside the superconducting state. This includes, for example, the generation of localized orbital current patterns or spin- polarization near atomic-scale impurities, twin boundaries and other defects. Signals of TRSB may also arise from a superconductivity-enhanced Ruderman- Kittel-Kasuya-Yosida exchange coupling between magnetic impurity moments present in the normal state. We discuss the relevance of these different mechanisms for TRSB in light of recent experiments on superconducting materials of current interest. [ABSTRACT FROM AUTHOR]

We report on a novel TaNbZrHfTi-based high entropy alloy (HEA) which demonstrates distinctive dual-phase superconductivity. The HEA was synthesized under high pressures and high temperatures starting from a ball milled mixture of elemental metals in a large-volume Paris–Edinburgh cell with P ≈ 6 GPa and T = 2300 K. The synthesized HEA is a phase mixture of BCC (NbTa)0.45(ZrHfTi)0.55 with Tc1 = 6 K and FCC (NbTa)0.04(ZrHfTi)0.96 with Tc2 = 3.75 K. The measured magnetic field parameters for the HEA are lower critical field, Hc1(0) = 31 mT, and a relatively high upper critical field, Hc2(0) = 4.92 T. This dual-phase system is further characterized by the presence of a second magnetization peak, or the fishtail effect, observed in the virgin magnetization curves. This phenomenon, which does not distort the field-dependent magnetization hysteresis loops, suggests intricate pinning mechanisms that could be potentially tuned for optimized performance. The manifestation of these unique features in HEA superconductivity reinforces phase-dependent superconductivity and opens new avenues in the exploration of novel superconducting materials. [ABSTRACT FROM AUTHOR]

(Cu,C)Ba2Ca3Cu4Oy is a nontoxic cuprate superconducting material with a superconducting transition temperature of about 116 K. Recently, it was found that bulk samples of this material synthesized under high pressure hold the highest irreversibility line among all the superconductors, which is very promising for its application in the liquid nitrogen temperature field. In this work, high-temperature (Cu,C)Ba2Ca3Cu4Oy superconducting films with large irreversible fields were prepared on SrLaAlO4(00l) substrates by pulsed laser deposition. The substrate temperature during deposition proved to be the most important parameter determining the morphology and critical temperature of the superconductors, with 680 °C considered to be the optimum temperature. X-ray diffraction (XRD) results showed that the (Cu,C)Ba2Ca3Cu4Oy films prepared under optimal conditions exhibited epitaxial growth with the a-axis perpendicular to the film surface and the b- and c-axes parallel to the substrate, with no evidence of any other orientation. In addition, resistivity measurements showed that the onset transition temperature (Tconset) was approximately 116 K, the zero-resistance critical temperature (Tc0) was around 53 K, and the irreversible field (Hirr) was about 9 T at 37 K for (Cu,C)Ba2Ca3Cu4Oy films under optimal temperature. This is the first example of the successful growth of superconducting (Cu,C)Ba2Ca3Cu4Oy films on SrLaAlO4(00l) substrates. This will facilitate high-performance applications of (Cu,C)Ba2Ca3Cu4Oy superconducting materials in the liquid nitrogen temperature field. [ABSTRACT FROM AUTHOR]

In order to cope with the grid fluctuation caused by large‐scale wind power connected to the grid, the wind thermal power generation system has been proposed and extensively studied. The wind thermal power generation system uses a wind turbine to drive a heat generation device to heat the heat storage medium, which is further exchanged to drive a turbine to generate electricity. A superconducting magnetic eddy current heater (SMH) is proposed for the characteristics of wind thermal power generation system, which uses non‐resistive, large current‐carrying superconducting coils for excitation, and has high output efficiency and power density. The working principle of magnetic eddy current heating is analysed, and the structure of SMH with no ferromagnetic material and two heating screens inside and outside is proposed according to the characteristics of SMH. An analytical model of the SMH is established, and the influence of the structure and materials of the SMH on the magnetic field distribution is analysed. Based on this, a 22‐pole SMH was designed and analysed for output power at 10–20 rpm. A three‐dimensional magnetism‐stress combined analysis model of SMH is established, and the strain and stress characteristics of SMH are simulated under the condition of maximum output power, which verifies the feasibility of the mechanical properties of existing superconducting materials for application in SMH. [ABSTRACT FROM AUTHOR]

The superconducting gap symmetry is crucial in understanding the underlying superconductivity mechanism. Angle-resolved photoemission spectroscopy (ARPES) has played a key role in determining the gap symmetry in unconventional superconductors. However, it has been considered so far that ARPES can only measure the magnitude of the superconducting gap but not its phase; the phase has to be detected by other phase-sensitive techniques. Here we propose a method to directly detect the superconducting gap sign by ARPES. This method is successfully validated in a cuprate superconductor Bi2Sr2CaCu2O8+δ with a well-known d-wave gap symmetry. When two bands have a strong interband interaction, the resulted electronic structures in the superconducting state are sensitive to the relative gap sign between the two bands. Our present work provides an approach to detect the gap sign and can be applied to various superconductors, particularly those with multiple orbitals like the iron-based superconductors. According to conventional wisdom, angle-resolved photoemission spectroscopy (ARPES) can only measure the magnitude of the superconducting gap but not its phase. Here, the authors propose a new method to directly detect the superconducting gap phase using ARPES and validate this technique on a cuprate superconductor. [ABSTRACT FROM AUTHOR]

Uniaxial stress has proven to be a powerful experimental tuning parameter for effectively controlling lattice, charge, orbital, and spin degrees of freedom in quantum materials. In addition, its ability to manipulate the symmetry of materials has garnered significant attention. Recent technical progress to combine uniaxial stress cells with quantum oscillation and angle-resolved photoemission techniques allowed to study the electronic structure as function of uniaxial stress. This review provides an overview on experimental advancements in methods and examines studies on diverse quantum materials, encompassing the semimetal WTe2, the unconventional superconductor Sr2RuO4, Fe-based superconductors, and topological materials. [ABSTRACT FROM AUTHOR]

High-temperature unconventional superconductivity quite generically emerges from doping a strongly correlated parent compound, often (close to) an antiferromagnetic insulator. The recently developed dynamical vertex approximation is a state-of-the-art technique that has quantitatively predicted the superconducting dome of nickelates. Here, we apply it to study the effect of pressure in the infinite-layer nickelate SrxPr1−xNiO2. We reproduce the increase of the critical temperature (Tc) under pressure found in experiment up to 12 GPa. According to our results, Tc can be further increased with higher pressures. Even without Sr-doping the parent compound, PrNiO2, will become a high-temperature superconductor thanks to a strongly enhanced self-doping of the Ni d x 2 − y 2 orbital under pressure. With a maximal Tc of 100 K around 100 GPa, nickelate superconductors can reach that of the best cuprates. The authors theoretically study the pressure dependence of the phase diagram of the nickelate PrNiO2 with and without Sr doping. At high pressure, they find that the superconducting dome is significantly enhanced in both Tc and doping-range of superconductivity compared with ambient pressure, with a maximal Tc of 100 K around 100 GPa in absence of external doping. [ABSTRACT FROM AUTHOR]

Analysis of the superconducting properties of transition metal dichalcogenides (TMDs) under high pressures offers valuable insights to guide the design and synthesis of high‐performance superconducting materials. Herein, the effect of pressure is investigated on the superconductivity of a typical van der Waals layered TMDs material, PdSSe, by measuring its transport properties. After initially increased pressure, superconductivity emerges at 10.2 GPa, with a critical superconducting temperature (Tc) of ≈5.1 K, accompanied by the diminishing charge density wave (CDW) that is originally strengthening. Then, the Tc gradually increases with increasing pressure, reaching 12.1 K at the maximum pressure. The study provides experimental evidence for the superconductivity of PdSSe, and to the best of the knowledge, this is the first report on the observation of amplified CDW phenomena under increasing pressure in nonmagnetic TMDs. The abnormal enhancement of CDW transition temperature at low pressure is consistent with the upward trend of resistance, which is related to the electron–electron interaction. Moreover, synchrotron X‐ray diffraction experiments reveal two additional structural phase transitions. [ABSTRACT FROM AUTHOR]

REBCO has been used extensively as coated conductors applied to superconducting magnets due to its exceptional superconducting properties. As a REBCO superconductor, YbBa2Cu3O7−y (Yb123) has a low melting temperature, making it suitable for use as an intermediate medium connector while preparing the superconducting joint. However, there is still uncertainty about the formation mechanism of Yb123 and the synthesis of this superconductor has not been fully understood. Therefore, this study systematically investigated the phase transformation process of Yb123 during heat treatment in flowing oxygen. The results indicated that Yb123 sample with the highest phase purity could be obtained by annealing at 927 °C or 937 °C but not in between, respectively. Furthermore, a quantitative phase analysis revealed that the sample annealed at 937 °C had a phase purity greater than 80 wt%. Additionally, a strong c-axis texture was observed in the bulk Yb123 superconductor prepared at 937 °C. Meanwhile, the superconducting results revealed that the bulk sample's Tc was 89.9 K, and its self-field critical current densities at 4.2 K and 77 K were 1.3 × 105 A/cm2 and 5.0 × 103 A/cm2, respectively. Based on the results mentioned above, the phase transformation process and formation mechanism of Yb123 in flowing oxygen were elaborated. [ABSTRACT FROM AUTHOR]

4Hb-TaS2 is a superconductor that exhibits unique characteristics such as time-reversal symmetry breaking, hidden magnetic memory, and topological edge modes. It is a naturally occurring heterostructure comprising of alternating layers of 1H-TaS2 and 1T-TaS2. The former is a well-known superconductor, while the latter is a correlated insulator with a possible non- trivial magnetic ground state. In this study, we use angle resolved photoemission spectroscopy to investigate the normal state electronic structure of this unconventional superconductor. Our findings reveal that the band structure of 4Hb-TaS2 fundamentally differs from that of its constituent materials. Specifically, we observe a significant charge transfer from the 1T layers to the 1H layers that drives the 1T layers away from half-filling. In addition, we find a substantial reduction in inter-layer coupling in 4Hb-TaS2 compared to the coupling in 2H-TaS2 that results in a pronounced spin-valley locking within 4Hb-TaS2. [ABSTRACT FROM AUTHOR]

The effect of artificially created 0D and 1D structural defects' nanostructure formed by implanted dielectric nanoparticles or irradiation defects on microwave properties of high-Tc superconductor films is analysed based on the phenomenological theory for microwave response of type-II superconductors. The surface resistance is calculated for the Meissner and mixed states for such a kind of nanostructured type-II superconductor film. An emergence of nonlinear response caused by the entrance of microwaveinduced vortices in the film interior through its edges is also theoretically explored. The obtained results demonstrate that artificial defect nanostructure inside the superconductor can significantly improve its microwave characteristics in both the Meissner states and the mixed ones and increase the range of the linear microwave response. We also present results of experimental studies on microwave properties of hightemperature superconductor (HTS) films with artificial defect nanostructure formed by heavy-ion irradiation. Noticeable decreases of the surface resistance and enhancement of the linear response range at low temperatures are observed for moderately perirradiated HTS YBa2Cu3O7-x (YBCO) film exposed to irradiation by 3 MeV Au2+ ions at dose 1011 cm-2. These results are in agreement with the above-discussed phenomenological theory for microwave response of nanostructured superconductors. A theoretical model concerning the new unusual mechanism of the nonlinear radio-frequency (RF) response in multiband superconductors is also presented. This is a mechanism of nonlinearity based on the possible dissociation of Abrikosov's vortices in multiband superconductors into fractional components under the strong RF current action. We have calculated the RF complex resistivity in two-band superconductors and grounded an emergence of specific peculiarities at critical current density values corresponding to the vortex depinning and dissociation. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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 ( ξ c (0) ), the irreversibility field ( B irr ), the upper critical magnetic field ( B c 2 ), the critical current density at T = 0 K ( J c (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 J c (0) for a sample with a non-optimized pinning landscape. [ABSTRACT FROM AUTHOR]

Motivated by the recently discovered high-Tc superconductor La3Ni2O7, we comprehensively study this system using density functional theory and random phase approximation calculations. At low pressures, the Amam phase is stable, containing the Y2− mode distortion from the Fmmm phase, while the Fmmm phase is unstable. Because of small differences in enthalpy and a considerable Y2− mode amplitude, the two phases may coexist in the range between 10.6 and 14 GPa, beyond which the Fmmm phase dominates. In addition, the magnetic stripe-type spin order with wavevector (π, 0) was stable at the intermediate region. Pairing is induced in the s±-wave channel due to partial nesting between the M = (π, π) centered pockets and portions of the Fermi surface centered at the X = (π, 0) and Y = (0, π) points. This resembles results for iron-based superconductors but has a fundamental difference with iron pnictides and selenides. Moreover, our present efforts also suggest La3Ni2O7 is qualitatively different from infinite-layer nickelates and cuprate superconductors. Recently superconductivity with Tc of about 80 K was discovered in a bilayer nickelate La3Ni2O7 under high pressure. Here the authors report a density functional theory and random phase approximation study of structural and electronic properties as a function of pressure and discuss the pairing mechanism. [ABSTRACT FROM AUTHOR]

Periodically driven systems provide a novel route to control the topology of quantum materials. In particular, Floquet theory allows an effective band description of periodically-driven systems through the Floquet Hamiltonian. Here, we study the time evolution of d-wave superconductors irradiated with intense circularly-polarized laser light. We consider the Floquet t–J model with time-periodic interactions, and investigate its mean-field dynamics by formulating the time-dependent Gutzwiller approximation. We observe the development of the idxy-wave pairing amplitude along with the original d x 2 − y 2 -wave order upon gradual increasing of the field amplitude. We further numerically construct the Floquet Hamiltonian for the steady state, with which we identify the system as the fully-gapped d + id superconducting phase with a nonzero Chern number. We explore the low-frequency regime where the perturbative approaches in the previous studies break down, and find that the topological gap of an experimentally-accessible size can be achieved at much lower laser intensities. Light-matter interaction provides advanced solutions to engineer quantum phases of matter. The authors unveil the emergence of a topological gap in superconductors when circularly polarized light impinges on the material, thereby disclosing accessible strategies to implement novel quantum technologies. [ABSTRACT FROM AUTHOR]

We have investigated the superconducting properties of nanocomposite pellets made from Bi-2223 and Co2C powders. Our measurements reveal loss of superconducting fraction in the nanocomposites. However, the retained superconducting fraction exhibits robust bulk superconducting properties. The Tc of the retained superconducting fraction was 109 K, which was found to be comparable to that of the pure Bi-2223 pellet. We found that the composite's net magnetization response is a superposition of the contributions of ferromagnetic and superconducting fractions. Analysis revealed that the surviving superconducting fraction exhibits a robust Meissner response. In the nanocomposite, the irreversibility field of the superconducting fraction at 77 K is found to increase by almost three times compared to the pristine material, thereby showing strong vortex pinning features. We also find a broadened magnetic field regime over which we observe that a single vortex pinning regime sustained in the nanocomposite. The critical current density, Jc, of the nanocomposite was found to be approximately five times higher than that of the pristine Bi-2223 pellet at low T. In fact, the enhancement in Jc is most significant in the high T regime, where at temperatures close to Tc in the nanocomposite, we see almost two orders of magnitude increase in Jc compared to the pristine Bi-2223 pellet. Our study suggests that larger sized agglomeration of magnetic nanoparticles of Co2C leads to loss of superconductivity in the nanocomposite. However, there are also unagglomerated Co2C nanoparticles distributed uniformly throughout the nanocomposite, which act as efficient pinning centers that allow for collective vortex pinning centers to be retained, even up to temperatures near Tc, and these nanoparticles also do not compromise the bulk Tc of the superconducting fraction. Our study shows that these nanocomposites that exhibit enhanced Jc especially in the high T regime are potentially useful for high current applications. [ABSTRACT FROM AUTHOR]

We investigate the influence of the Abrikosov vortex lattice on the Casimir force in a setup constituted by high-temperature superconductors subject to an external magnetic field. The Abrikosov lattice is a property of type II superconductors in which normal and superconducting carriers coexist and the latter define a periodic pattern with square symmetry. We find that the optical properties determined by spatial redistribution of the superconducting order parameter induce Casimir forces with a periodic structure whose minimal strengths coincide with the vortex cores. [ABSTRACT FROM AUTHOR]

Hole-doped high-temperature copper oxide-based superconductors (cuprates) exhibit complex phase diagrams where electronic orders like a charge density wave (CDW) and superconductivity (SC) appear at low temperatures. The origins of these electronic orders are still open questions due to their complex interplay and correlated nature. These electronic orders can modify the phonons in the system, which has also been experimentally found in several cuprates as a softening in the phonon frequency at the CDW vector. Recent experiments have revealed that the softening in phonons in cuprates due to CDW shows intriguing behavior with increasing hole doping. Hole doping can also change the underlying Fermi surface. Therefore, it is an interesting question whether the doping-induced change in the Fermi surface can affect the softening of phonons, which in turn can reveal the nature of the electronic orders present in the system. In this work, we investigate this question by studying the softening of phonons in the presence of CDW and SC within a perturbative approach developed in an earlier work. We compare the results obtained within the working model to some experiments. [ABSTRACT FROM AUTHOR]

Stacking and twisting graphene layers allows to create and control a two-dimensional electron liquid with strong correlations. Experiments indicate that these systems exhibit strong tendencies towards both magnetism and triplet superconductivity. Motivated by this phenomenology, we study a 2D model of fluctuating triplet pairing and spin magnetism. Individually, their respective order parameters, d and N, cannot order at finite temperature. Nonetheless, the model exhibits a variety of vestigial phases, including charge-4e superconductivity and broken time-reversal symmetry. Our main focus is on a phase characterized by finite d ⋅ N, which has the same symmetries as the BCS state, a Meissner effect, and metastable supercurrents, yet rather different spectral properties: most notably, the suppression of the electronic density of states at the Fermi level can resemble that of either a fully gapped or nodal superconductor, depending on parameters. This provides a possible explanation for recent tunneling experiments in the superconducting phase of graphene moiré systems. P. Poduval et al. theoretically study the nonzero-temperature vestigial phases of a 2D model exhibiting both triplet superconductivity and magnetism. They show that this model allows for a unique superconducting state in which the condensate consists of entities with three electrons and one hole, with properties similar to those seen in experiments on moiré systems. [ABSTRACT FROM AUTHOR]

Herein, the preparation process, morphology, structure, and magnetic properties of La1.85Sr0.15CuO4 (LSCO) cobweb-like nanofibers are reported. LSCO nanofibers with a regular grain size distribution are successfully prepared via electrospinning, followed by calcination. We conducted morphology analysis and elemental distribution using electron microscopy and energy-dispersive X-ray spectroscopy (EDS), respectively. Additionally, magnetic property testing was performed using a vibrating sample magnetometer (VSM) to confirm the superconducting properties of the samples. Interestingly, our samples exhibited a superconducting transition temperature, Tc, of 25.21 K, which showed some disparity compared to similar works. Furthermore, we observed a ferromagnetic response at low temperatures in the superconducting nanofibers. We attribute these phenomena to the effects generated by surface states of nanoscale superconducting materials. [ABSTRACT FROM AUTHOR]