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The generation of Sz = 1 triplet Cooper pairs has been predicted theoretically in superconducting–ferromagnetic hybrid heterostructures in the presence of spin–orbit coupling [F. S. Bergeret and I. V. Tokatly, Phys. Rev. B 89, 134517 (2014) and Jacobsen et al., Sci. Rep. 6, 23926 (2016)]. In this study, we experimentally investigate vertical Josephson junctions where the weak link is formed from a ferromagnetic layer with perpendicular magnetic anisotropy sandwiched by two non-magnetic layers with weak or strong spin–orbit coupling. We find that the decay of the Josephson coupling is reduced in the latter case, possibly indicating the presence of Sz = 1 spin-triplet correlations. We speculate that the canted magnetization required for these correlations is provided by the interaction of magnetization with Meissner effect in the superconducting layers. [ABSTRACT FROM AUTHOR]

Superconducting phase transitions in two dimensions lie beyond the description of the Ginzburg-Landau symmetry-breaking paradigm for three-dimensional superconductors. They are Berezinskii-Kosterlitz-Thouless (BKT) transitions of paired-electron condensate driven by the unbinding of topological excitations, i.e. vortices. The recently discovered monolayers of layered high-transition-temperature (⁠|${{{T}}}_{{\rm C}}$|⁠) cuprate superconductor Bi2Sr2CaCu2O8+δ (Bi2212) meant that this 2D superconductor promised to be ideal for the study of unconventional superconductivity. But inhomogeneity posed challenges for distinguishing BKT physics from charge correlations in this material. Here, we utilize the phase sensitivity of scanning superconducting quantum interference device microscopy susceptometry to image the local magnetic response of underdoped Bi2212 from the monolayer to the bulk throughout its phase transition. The monolayer segregates into domains with independent phases at elevated temperatures below |${{{T}}}_{{\rm C}}$|⁠. Within a single domain, we find that the susceptibility oscillates with flux between diamagnetism and paramagnetism in a Fraunhofer-like pattern up to |${{{T}}}_{{\rm C}}$|⁠. The finite modulation period, as well as the broadening of the peaks when approaching |${{{T}}}_{{\rm C}}$| from below, suggests well-defined vortices that are increasingly screened by the dissociation of vortex-antivortex plasma through a BKT transition. In the multilayers, the susceptibility oscillation differs in a small temperature regime below |${{{T}}}_{{\rm C}}$|⁠ , consistent with a dimensional crossover led by interlayer coupling. Serving as strong evidence for BKT transition in the bulk, we observe a sharp jump in phase stiffness and paramagnetism at small fields just below |${{{T}}}_{{\rm C}}$|⁠. These results unify the superconducting phase transitions from the monolayer to the bulk underdoped Bi2212, and can be collectively referred to as the BKT transition with interlayer coupling. [ABSTRACT FROM AUTHOR]

Considerations on the current status of the theory of superconductivity, the bibliometric H-index, and H. C. Andersen's tale about the emperor's new clothes. First appeared in the APS Forum on Physics and Society quarterly newsletter, January 2020. [ABSTRACT FROM AUTHOR]

A sharp jump in the magnetic response near the first critical twins magnetic field Hic1 was generated under the combined action of a constant biased and a local oscillating damped magnetic fields on the surface of the YBa2Cu3O7 –x epitaxial film. The possibility of increasing due to this jump the sensitivity of a standard Hall magnetometer from ~2.5 × 10–3 G/Hz1/2 to ~8 × 10–7 G/Hz1/2 in the frequency range ~1 kHz has been demonstrated. The range of the measured magnetic fields of the magnetometer was extended to the region of weak fields ~(8 × 10–7–2.5 × 10–3) Oe, while maintaining the accuracy and linearity of the order of ~0.01%. To increase the sensitivity, linearity and noise sustainability the beginning of the operating point of the magnetometer was shifted to the twins values Hic1. The increased spatial resolution of the magnetometer, determined by the linear dimensions of the YBa2Cu3O7 –x film twins, was provided by an increase in the total magnetic field directed perpendicular to the film surfaces and the Hall transducer and reached ~ 300 nm. [ABSTRACT FROM AUTHOR]

An attempt is made to describe from first principles the large-scale structure of the confining vacuum in quantum chromodynamics. Starting from our previous variational studies of the SU(2) pure gauge theory in an external Abelian chromomagnetic field and extending Feynman's qualitative analysis in (2+1)-dimensional SU(2) gauge theory, we show that the SU(3) vacuum in three-space and one-time dimensions behaves like a disordered chromomagnetic condensate. Color confinement is assured by the presence of a mass gap together with the absence of color long-range correlations. We offer a clear physical picture for the formation of the flux tube between static quark charges that allows us to determine the color structure and the transverse profile of the flux-tube chromoelectric field. The transverse profile of the flux-tube chromoelectric field turns out to be in reasonable agreement with lattice data. We, also, show that our quantum vacuum allows for both the color and ordinary Meissner effect. We find that for massless quarks, the quantum vacuum can accommodate a finite non-zero density of fermion zero modes leading to the dynamical breaking of the chiral symmetry. [ABSTRACT FROM AUTHOR]

We explore the state of matter characterized by the charged timelike vector order parameter. We employ holographic duality in order to construct such a state and study its thermoelectric transport, fermionic spectral function and the character of the Meissner effect. We uncover the unusual features of this "timelike superconductor": the absence of the gap in the fermionic spectrum and co-existence of Drude peak and supercurrent in the AC transport, which are reminiscent to those of time-reversal-odd and gapless superconductors, correspondingly. We show that this state is dynamically stable and thermodynamically at least metastable. Along the way we develop the holographic model of the charged vector field, which acquires mass due to a variant of the Stueckelberg mechanism with the adjoint Higgs field. [ABSTRACT FROM AUTHOR]

Imaging local magnetic fields produced by nano- and micrometer-scale superconductors has become a vital tool that can not only reveal crucial information on the vortex dynamics and order parameters of the superconducting materials but also visualize the working mechanism of superconducting devices made for quantum information. Here, we performed measurements of the magnetic field distributions of mesoscopic superconducting structures with various geometries by combining a thin ferromagnetic metal layer as a magneto-optical sensing element that responds to the environmental magnetic fields and a custom-made sensitive Sagnac interferometer. The sensitivity of the technique enables the observation of magnetic flux jumps due to individual vortex entries into nanostructured superconductors. In addition, with the control of incident power at a focused laser spot, we induce thermally driven movement of vortices that leaves a trace of a microscopic optical heating pattern. [ABSTRACT FROM AUTHOR]

This article discusses the use of magnetic methods in studying new superconducting hydrides in a diamond anvil cell (DAC). The high-pressure experiments have led to the discovery of high-transition-temperature (Tc) hydrides by creating metallic hydrogen 'alloys' with other elements. However, measuring the complete expulsion of the magnetic field, known as the Meissner state, in these hydrides is challenging due to the high pressures required. The article provides a summary of four alternative techniques used to probe the Meissner state in a DAC, including the AC susceptibility method, the double-modulation technique, SQUID magnetometry, and the NV− magnetometry. The authors argue that the growing experimental evidence supports the claims about superhydrides as nearly room-temperature superconductors. [Extracted from the article]

This article discusses the advancements in high-temperature superconductivity in hydrogen-rich materials. It highlights the discovery of superconductivity in hydrogen sulphide (H3S) and other hydride-rich hydrides, which have shown promising results at high pressures. The article emphasizes the reproducibility of superconductivity under challenging experimental conditions and the potential for achieving room-temperature superconductivity in the near future. The importance of experimental research and the synergy between theory and experiment are also emphasized, as well as the need for further exploration in the search for new superconductors. [Extracted from the article]

The article discusses the pursuit of room-temperature superconductivity (RTSC) and the potential of hydrogen-rich materials (hydrides) to achieve this goal. It highlights the recent advancements in the synthesis and characterization of binary hydride superconductors with high critical temperatures (Tc) exceeding 100 K. The article also explores the potential of ternary superhydrides, which offer more diverse structure variants and chemical compositions, to further enhance Tc and reduce the required pressures. Experimental progress in synthesizing ternary superconducting hydrides is discussed, along with the challenges in identifying superconducting phases and characterizing their properties. The article concludes by emphasizing the need for further developments in high-pressure techniques and in-situ characterizations to address these challenges. [Extracted from the article]

This document is an editorial titled "The impact of internal and external influences on memory and their relevance to legal decisions." It discusses the effects of internal and external influences on memory accuracy and their implications for legal proceedings. The editorial highlights various studies on topics such as memory conformity, misinformation effects, stress, and the role of emotions in memory. It emphasizes the need for further research in understanding both internal and external influences on memory and provides practical information for legal practitioners to avoid detrimental effects on memory and legal decisions. [Extracted from the article]

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]

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]

The effects of hybridization and impurity (magnetic and nonmagnetic) potentials on the pairing symmetries and magnetic response of a two-band superconductor with an equal-time s -wave interband pairing order parameter in the framework of Green's function technique are investigated theoretically. First, the effects of spin-independent and spin-dependent hybridization on the generation of even- or odd-frequency Cooper pairs which determines the symmetry classification and the response of the superconductor are studied. Next, the impurity effect on creating different symmetry classes and the kernel response function of a two-band superconductor are discussed. By separating the contributions of even- and odd-frequency pairing to the Meissner kernel, it is shown that the competition between these two terms determines the total Meissner effect of the superconductor. For a two-band spin-singlet superconductor, nonmagnetic impurity scatterings do not change transition temperature according to Anderson's theorem, while both intra- and interband magnetic impurity scattering cause superconducting transition temperature suppression with the rate following the Abrikosov–Gor'kov theory. For spin-triplet pairing, interband magnetic scattering has no impact on pair breaking, whereas intraband magnetic scattering acts as a pair breaker and suppresses the transition temperature in the Born limit. In this case, the odd-frequency superconducting pairs can be induced in the simultaneous presence of both intra- and interband magnetic impurities. Thus, by controlling the concentration of magnetic impurities, it is possible to engineer triplet-pairing odd-frequency superconductors with a total diamagnetic Meissner response which stabilizes the superconducting state. This technique opens up an avenue for designing stable odd-frequency superconductors. [ABSTRACT FROM AUTHOR]

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

Under the spell of BCS-electron–phonon theory [M. Tinkham, Introduction to Superconductivity, 2nd ed. (McGraw Hill, New York, 1996)], during the last 6 years experimentalists have purportedly discovered a plethora of high temperature conventional superconductors among pressurized hydrides [Pickard et al., Ann. Rev. Condens. Matter Phys. 11, 57 (2020) and R. F. Service, Science 373, 954 (2021)], and theorists have been busy predicting and explaining those findings [Lv et al., Matter Radiat. Extremes 5, 068101 (2020); Flores-Livas et al., Phys. Rep. 856, 1 (2020); and Boeri et al., J. Phys. Condens. Matter. (to be published)]. The alternative theory of hole superconductivity (see https://jorge.physics.ucsd.edu/hole.html for a list of references) predicts instead that no superconductivity can exist in these materials. In this Tutorial, I will first argue that, unclouded by the prejudice of BCS's validity, the existing experimental evidence for superconductivity in pressurized hydrides does not withstand scrutiny. Once it is established that superconductivity in pressurized hydrides is a myth and not a reality, the claim to validity of BCS-electron–phonon theory as a descriptor of superconductivity of real materials will be forever shattered, and an alternative theory will become imperative. I will explain the fundamentals of the theory of hole superconductivity, developed over the past 32 years [see https://jorge.physics.ucsd.edu/hole.html and J. E. Hirsch, Phys. Lett. A 134, 451 (1989)], and why it is compelling. Crucially, it explains the Meissner effect, that I argue the conventional theory does not. It applies to all superconducting materials and provides guidelines in the search for high temperature superconductors that are very different from those provided by BCS-electron–phonon theory. Light elements are predicted to be irrelevant to warm superconductivity because according to this theory the electron–phonon interaction plays no role in superconductivity. [ABSTRACT FROM AUTHOR]

Superconductors are materials with zero electrical resistivity and the ability to expel magnetic fields, which is known as the Meissner effect. Their dissipationless diamagnetic response is central to magnetic levitation and circuits such as quantum interference devices. In this work, we used superconducting diamagnetism to shape the magnetic environment governing the transport of spin waves—collective spin excitations in magnets that are promising on-chip signal carriers—in a thin-film magnet. Using diamond-based magnetic imaging, we observed hybridized spin-wave– Meissner-current transport modes with strongly altered, temperature-tunable wavelengths and then demonstrated local control of spin-wave refraction using a focused laser. Our results demonstrate the versatility of superconductor-manipulated spin-wave transport and have potential applications in spin-wave gratings, filters, crystals, and cavities. [ABSTRACT FROM AUTHOR]

The article reports on a universal mechanism for the Josephson diode effect in short Josephson junctions, which is attributed to finite Cooper pair momentum and simultaneous breaking of inversion and time-reversal symmetries, resulting in a diode efficiency of up to 40%. This mechanism expands the platforms for observing super current diode effects without relying on spin-orbit coupling.

Granular high-temperature superconductors (HTSs) are characterized by the hysteretic field dependences of magnetoresistance R(H) and critical current IC(H). These hysteretic effects are described within the concept of an effective field in the intergrain medium. The effective field is a superposition of external magnetic field H and the field induced by the magnetic moments of superconducting grains into intergrain spacings (grain boundaries). The magnetization of superconducting grains is determined by two contributions: Meissner (shielding) currents (MC) and trapped magnetic fluxes (Abrikosov vortices (AV)). To develop the concept of an effective field in the intergrain medium, the magnetotransport properties (R and IC) have been compared for two cases: (AV) the magnetization of superconducting grains is only determined by the trapped magnetic flux (zero external field) and (MC) HTS grains are in the Meissner state (the external field is weaker than the first critical field of grains). In a set of experiments, the main features of the hysteretic R(H) and M(H) dependences have been illustrated and the external conditions for implementing the AV and MC states have been established. It has been found that the effects of the Abrikosov vortices and intragrain Meissner currents on an effective field in the intergrain medium at the same magnetization values are noticeably different. This is a nontrivial fact that requires a thorough study of the impact of the anisotropy of the superconducting properties of grains on the configuration of the Meissner currents in them, as well as on the orientation of vortices both inside grains and near their surface. We suggest the explanation of observed stronger effect of the Meissner currents on the intergrain medium as compared with the effect of the Abrikosov vortices. [ABSTRACT FROM AUTHOR]

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The electronically nematic order has emerged as a key feature of cuprate superconductors, however, its correlation with the fundamental properties such as the electromagnetic response remains unclear. Here the nematic-order state strength dependence of the electromagnetic response in cuprate superconductors is investigated within the framework of the kinetic-energy-driven superconductivity. It is shown that a significant anisotropy of the electromagnetic response is caused by the electronic nematicity. In particular, in addition to the pure d-wave component of the superconducting gap, the pure s-wave component of the superconducting gap is generated by the electronic nematicity, therefore there is a coexistence and competition of the d-wave component and the s-wave component. This coexistence and competition leads to that the maximal condensation energy appears at around the optimal strength of the electronic nematicity, and then decreases in both the weak and strong strength regions, which in turn induces the enhancement of superconductivity, and gives rise to the dome-like shape of the nematic-order state strength dependence of the superfluid density. [ABSTRACT FROM AUTHOR]

The penetration depth is a magnetic field mechanism by which an external magnetic field penetrates into superconductors' surfaces and is related to the Meissner effect. The penetration depth property was studied by the semiclassical approach to identify other properties of superconductors. In this study, we investigated the penetration depth of the H3S superconductor under external pressure. The H3S superconductor is high Tc, s-wave isotropic, and high pressure prepared superconductors. We derive an analytical equation for the near-zero temperature penetration depth with pressure effect parameters. The derived equations were then numerically calculated and predicted the experimental data on H3S superconductor penetration depth. We discovered that the temperature dependent penetration depth under pressure of H3S superconductor is reasonable at Tc(χ = 473, ε0 = 91,Qp = 0.1) = 200.832 K., as well as is the influence of the directly χ parameter on Tc(χ,ε0, Qp), Δ(0,χ, ε0,Qp), and λ(T,χ,ε0,Qp), with Qp>0.1 does not corresponding theory [ABSTRACT FROM AUTHOR]

Most aircraft launchers exhibit a rapid acceleration of the launching aircraft, often exceeding ten times the acceleration due to gravity. However, only magnetic launchers offer flexible control over the propulsion force of the launcher cart, enabling precise control over the aircraft's acceleration and speed during its movement on the launcher. Consequently, extensive research is being conducted on magnetic launchers to ensure the repeatability of launch parameters, protect against aircraft overloads, and ensure operator safety. This article describes the process of modeling and analyzing the dynamical properties of a launch cart of an innovative prototype launcher, which employs a passive magnetic suspension with high-temperature superconductors, developed under the GABRIEL project. The developed mathematical model of the magnetic catapult cart was employed to conduct numerical studies of the longitudinal and lateral movement of the cart, as well as the configuration of the UAV–cart system during UAV takeoff under variable atmospheric conditions. An essential aspect of the research involved experimentally determining the magnetic levitation force generated by the superconductors as a function of the gap. The results obtained demonstrate that the analyzed catapult design enables safe UAV takeoff. External factors and potential vibrations resulting from uneven mass distribution in the UAV–cart system are effectively balanced by the magnetic forces arising from the Meissner effect and the flux pinning phenomenon. The primary advantage of the magnetic levitation catapult, in comparison to commercial catapults, lies in its ability to provide a reduced and consistent acceleration throughout the entire takeoff process. [ABSTRACT FROM AUTHOR]

Compressed hydrogen-rich compounds have been verified extensively by theoretical scientists for finding high-temperature superconductivity. Although some experiments confirm these findings, their requirement of extremely high critical pressure condition ( 100 GPa ≲ P c ) makes them impossible to apply in daily life. The main purpose of present work is to help finding materials with high-temperature superconductivity at low pressures. For this purpose, we consider two graphene sheets with sine form corrugations whose honeycomb patterns are exactly on top of each other with some doped molecules intercalated into sheets. The free energy of valence electrons of total atoms is computed for doped molecules PrH 6 , PrH 7 , PrH 8 , and PrH 9 , separately. Our calculations indicate a second-order phase transition for PrH 9 at critical temperature T c = 179.01 K with applying no external pressure, while no phase transition is observed for other doped molecules. This high-temperature electronic structural stability is 46 K greater than the T c of the cuprate materials which are the highest-temperature superconductors at low pressures. We guess this phase transition is a superconductivity transition due to the observation of Meissner effect in magnetic susceptibility diagram. [ABSTRACT FROM AUTHOR]

The experimental data in the literature concerning the Paramagnetic Meissner Effect (PME) or also called Wohlleben effect are reviewed with the emphasis on the PME exhibited by metallic, s-wave superconductors. The PME was observed in field-cool cooling (FC-C) and field-cool warming (FC-W) m (T) -measurements on Al, Nb, Pb, Ta, in compounds such as, e.g., NbSe 2 , In-Sn, ZrB 12 , and others, and also in MgB 2 , the metallic superconductor with the highest transition temperature. Furthermore, samples with different shapes such as crystals, polycrystals, thin films, bi- and multilayers, nanocomposites, nanowires, mesoscopic objects, and porous materials exhibited the PME. The characteristic features of the PME, found mainly in Nb disks, such as the characteristic temperatures T 1 and T p and the apparative details of the various magnetic measurement techniques applied to observe the PME, are discussed. We also show that PME can be observed with the magnetic field applied parallel and perpendicular to the sample surface, that PME can be removed by abrading the sample surface, and that PME can be introduced or enhanced by irradiation processes. The PME can be observed as well in magnetization loops (MHLs, m (H) ) in a narrow temperature window T p < T c , which enables the construction of a phase diagram for a superconducting sample exhibiting the PME. We found that the Nb disks still exhibit the PME after more than 20 years, and we present the efforts of magnetic imaging techniques (scanning SQUID microscopy, magneto-optics, diamond nitrogen-vacancy (NV)-center magnetometry, and low-energy muon spin spectroscopy, (LE- μ SR)). Various attempts to explain PME behavior are discussed in detail. In particular, magnetic measurements of mesoscopic Al disks brought out important details employing the models of a giant vortex state and flux compression. Thus, we consider these approaches and demagnetization effects as the base to understand the formation of the paramagnetic signals in most of the materials investigated. New developments and novel directions for further experimental and theoretical analysis are also outlined. [ABSTRACT FROM AUTHOR]

When approaching extremality, rotating black holes tend to expel the magnetic field in which they are immersed. This phenomenon, being reminiscent of the Meissner-Ochsenfeld effect in superconductors, is known as the black hole Meissner effect, and here we study it in the backreacting regime and from the near horizon perspective. By resorting to methods recently developed in the literature, which allow to compute conserved charges in the near horizon region, regardless the details of the asymptotia at large distance, we investigate the properties of the black hole horizon when in its Meissner state. We show that, when in such state, the horizon exhibits two sets of supertranslation symmetries as well as a symmetry generated by the local conformal group. The supertranslations are generated by two infinite sets of currents, one of which comes from local dilations of the advanced null coordinate at the horizon, and the other from local gauge transformations that preserve the electromagnetic field configuration at the horizon. We show that the evaluation of the conserved charges associated to these symmetries correctly reproduce the physical charges of the magnetized black holes and their thermodynamics. This represents a concrete application of the techniques developed in [1–3] and it extends the results of [4] to arbitrary values of the black hole charges. In addition, we elaborate on the charges computation at the horizon: we show the equivalence between the horizon charges and the evaluation of the corresponding Komar integrals. Besides, we show the validity of the Gauss phenomenon by explicitly relating near horizon charges with fluxes and charges computed by other techniques. All this provides a method to derive the thermodynamics of magnetized horizons in a quite succinct way, including the case of horizons exhibiting the Meissner effect. [ABSTRACT FROM AUTHOR]

We investigate correspondence between the Melvin–Kerr–Newman–Taub–NUT spacetime, and the conformal field theory. The near horizon geometry of extremal Melvin–Kerr–Newman–Taub–NUT spacetime possesses the S L 2 , R × U 1 isometry, which allows one to employ the asymptotic symmetry group method, in establishing the holographic correspondence for the spacetime. We also use the alternative way of the stretched horizon method, to compute the extremal entropy of the black hole. We find perfect agreement between the results of asymptotic symmetry group and the stretched horizon methods, to establish the holography for the extremal Melvin–Kerr–Newman–Taub–NUT black hole. The black hole Meissner effect for the Melvin–Kerr–Taub–NUT black hole is also discussed. [ABSTRACT FROM AUTHOR]

Reference [1] presents evidence for magnetic field screening and "subtle" evidence for magnetic field expulsion in hydrides under high pressure, which is argued to support the claim that these materials are high temperature superconductors. We point out here that data presented in different figures of Ref. [1] are inconsistent (i) with one another, (ii) with other work by the same authors on the same samples [2-3], and (iii) with the expected behavior of standard superconductors. This suggests that these magnetic phenomena reported for these materials are not associated with superconductivity, undermining the claim that these materials are high temperature superconductors. [ABSTRACT FROM AUTHOR]

The accidental discovery of mercury's zero resistance at temperatures lower than 4.2 K which took place in 1911 by the Dutch physicist Heike Kamerlingh Onnes in his laboratory at the University of Leiden, appeared to be one of the greatest breakthroughs of physics of all time. It has led to the creation of an entirely new field within physics called superconductivity; this attracted many of the finest minds in physics whose work in this area produced no less than six Nobel Prizes to date. Zero resistance, together with the expulsion of magnetic fields which was discovered many years later, are the two unique and intriguing properties of superconductors which puzzled scientists' brains for a proper theoretical explanation of the observed phenomena. However in 1935, the phenomenological theory proposed by Fritz and Heinz London (known as the London theory) was the first success in the field, which was followed in the 1950s by another phenomenological theory put forward by Vitaly Ginzburg and Lev Landau. Despite this, a satisfactory microscopic theory for superconductivity had to wait until 1957 when John Bardeen, Leon Cooper and John Robert Schrieffer proposed their theory, which was nicknamed the BCS theory in their honour. The more recent discovery of the cuprate high temperature superconductors (HTS) in 1986 gave a new momentum to the field and intensified the search for room temperature superconductors which continues to this day. While this quest is under way, and new theories of superconductivity are being developed, physicists, material scientists and engineers are using superconductors to establish new technologies and build machines, devices and tools with unprecedented properties. Today superconductors are widely used in healthcare, particle accelerators, ultrasensitive instrumentation and microwave engineering and they are being developed for use in many other areas as well. In this review, we will trace the history of superconductors and provide a brief overview into some of the recent applications of superconductivity. [ABSTRACT FROM AUTHOR]

We show that magnetic monopoles appear naturally in granular quantum matter. Their condensation leads to a new state of matter, superinsulation, in which Cooper pairs are bound into purely electric pions by strings of electric flux. These electric flux tubes, the dual of Abrikosov vortices, prevent the separation of charge–hole pairs, thereby causing an infinite resistance, even at finite temperatures, the dual behaviour of superconductors. We will discuss the electric Meissner effect, asymptotic freedom and their measurements and describe the recent direct detection of a linear, confining potential by dynamic relaxation experiments. Finally, we consider dyons, excitations carrying both a magnetic and an electric charge, and show that a condensate of such dyons leads to a possible solution of the mysteries of the pseudogap state of high- T c cuprates. [ABSTRACT FROM AUTHOR]

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.

In the present work, we report the synthesis of Pb–Bi alloy with enhanced T c of up to 9K, which is higher than that of Pb. The alloy is synthesized via a solid-state reaction route in the vacuum-encapsulated quartz tube at 700°C in an automated furnace. The synthesized sample is characterized by X-ray Diffraction(XRD) and Energy dispersive X-ray analysis(EDAX) for its phase purity and elemental composition. Rietveld refinement of XRD reveals that the end product is a majority hexagonal Pb 7 Bi 3 , with minor rhombohedral Bi. The electronic transport measurement shows metallic behavior with the Debye temperature of 108K and a superconductivity transition temperature (T c) below 9K, which is the maximum to date for any reported Pb–Bi alloy, Pb or Bi at ambient pressure. Partial substitution of Bi at the Pb site may modify the free density of electronic states within the BCS model to attain the optimum T c , which is higher by around 2K from the reported T c of Pb. The superconductor phase diagram derived from magneto-transport measurements reveals that the synthesized alloy is a conventional superconductor with an upper critical field (H c2) of 3.9 T, which lies well within the Pauli paramagnetic limit. The magnetization measurements carried out following ZFC(Zero Field Cool) protocols infer that the synthesized alloy is a bulk superconductor below 9K. The isothermal M-H(Magnetization vs. Field) measurements performed below T c establish it as a type-II superconductor. The specific heat capacity measurements show that the Pb–Bi alloy is a strongly coupled bulk superconductor below around 9K with possibly two superconducting gaps. • This article reports the successful synthesis and characterization of Pb–Bi Alloy with T c at ∼ 9K. • The magneto-transport and magnetization measurements elucidate the presence of type-II superconductivity in Pb–Bi alloy. • The paramagnetic Meissner effect is observed in FC magnetization measurement. • Bulk superconductivity is endorsed by heat capacity measurement, with strong coupling. [ABSTRACT FROM AUTHOR]

The utilization of high-hardness superconducting materials enhances and broadens the applications of superconductors. In this study, a high-hardness Mo 2 BC superconductor is synthesized using the high-pressure and high-temperature (HPHT) method. Our results demonstrate that it exhibits zero-resistance and Meissner effect below a superconducting critical temperature (T c) of 7.0 K. The upper critical magnetic field of 4.3 T and the lower critical magnetic field of 226 Oe were obtained by data fitting, respectively. Type-II superconducting properties were confirmed by critical states analysis and Ginzburg-Landau (GL) parameters. Specific thermal properties revealed a Debye temperature as 565.1 K, while an electron-phonon coupling (EPC) parameter λ of 0.588 indicated properly coupled BCS conventional superconductivity. Mo 2 BC exhibits a Vickers hardness of up to 18.2 GPa, significantly surpassing that of traditional superconducting ceramics. It can be attributed to the robust covalent boron-zigzag-chains coupled with appropriate covalent [Mo 6 C] octahedrons within a non-centrosymmetric structure. The coexistence of both superconductivity and high hardness enables the versatility of Mo 2 BC, thereby laying the way for the development of high-hardness superconductors. • High density single phase Mo 2 BC was synthesized by high-pressure high-temperature method. • Good electrical conductivity, type-II superconductivity, and complete superconducting parameters are elucidated in Mo 2 BC. • The hardness of Mo 2 BC is far higher than the traditionally used superconducting ceramics. • The high hardness is attributed to the strong covalent boron-zigzag-chains coupled with appropriate covalent octahedrons. [ABSTRACT FROM AUTHOR]

YBa 2 Cu 3 O y (Y-123) is one of the most intensively studied high-temperature superconductors (HTS) and has great potential for applications in electronics. Its superconducting properties significantly depend on the oxygen index (y), the peculiarities of the atomic crystal and microgranular structure, the type and concentration of contaminating atoms. Therefore, of particular interest are the techniques of HTS synthesis that significantly affect the superconducting properties, as well as modifications of these techniques. The aim of this study was to investigate the effect of ultrahigh dilution (UHD) technology on the Y-123 HTS properties. We applied UHD technology to treat Y 2 O 3 ·4BaO 2 ·6CuO composition (before and/or after calcination) and used solid-phase reaction to obtain batches of ceramic samples of the Y-123 phase. Main characteristics of the synthesized HTS specimens (the orthorhombic unit cell parameters, temperature dependence of electrical resistance, Meissner effect, and critical current density) were studied. X-ray phase analysis demonstrated that the samples were practically single-phase and consisted of the Y-123 phase. Depending on the treatment method, the modifying effect varied. Positive and most significant results were demonstrated for specimens obtained from precursor powder mixture treated with UHD. For some of such specimens an increase in the temperature of the beginning of the transition to the superconducting state by 3.8 K, the Meissner effect by 9%, and the density of the intergranular critical current by 35% were observed. We conclude that UHD technology can be used to improve properties of HTS. However, methodology for implementation of UHD technology should depend on which specific superconductor property needs to be changed. [ABSTRACT FROM AUTHOR]

In this study, an experimental design was employed to optimize the fabrication of the YCa 2 Cu 3 O 7 superconductor composite. The superconductors were fabricated using biocompatible calcium carbonate nanoparticles extracted from cuttlebone, Sepia pharaonis, of the Persian Gulf in the Bushehr coastal area, and their effects on YCa 2 Cu 3 O 7 superconductor's properties were investigated. Ball milling process and solid-state calcination reaction were used for obtaining the natural calcium carbonate nanoparticles and fabrication of the superconductors, respectively. The effects of three factors, milling time and the excess amount of the natural calcium carbonate as well as yttrium oxide, were investigated on the superconductivity properties of the products. The Taguchi statistical design of experiments was conducted to reveal the sensitivity analysis of the products' properties due to the variation in each variable, finding optimal production conditions, and reduction in the total number of required experiments. In this method, the oxygen content of the fabricated superconductor was considered as the targeted YCa 2 Cu 3 O 7 property. Moreover, the morphology and structural properties of the products were investigated to find the relationship between physicochemical properties and superconductivity. The YCa 2 Cu 3 O 7 superconductors were characterized by the Meissner effect test, XRD analysis, and FESEM imaging. The sensitivity analysis was shown that by increasing milling time and the excess amount of the reactants in the solid-state reaction, the connectivity and crystallization of the grains were improved, and the optimum operating conditions for the production were achieved. Besides, the variation in milling time causes more signal-to-noise ratio, which indicates the highest efficacy of this factor on the superconductivity of the products in comparison with the other variables. [ABSTRACT FROM AUTHOR]

The Meissner effect, magnetic field expulsion, is a hallmark of superconductivity. Associated with it, superconductors exclude applied magnetic fields. Recently, Minkov et al. [Nat. Commun. 13, 3194 (2022)] presented experimental results reportedly showing "definitive evidence of the Meissner effect" in sulfur hydride and lanthanum hydride under high pressure, and Eremets et al. [J. Supercond. Nov. Magn. 35, 965 (2022)] argued that "the arguments against superconductivity (in hydrides) can be either refuted or explained." Instead, we show here that the evidence presented in those papers does not support the case for superconductivity in these materials. Together with experimental evidence discussed in earlier papers, we argue that this strongly suggests that hydrides under pressure are not high-temperature superconductors. [ABSTRACT FROM AUTHOR]

The experimental data in the literature concerning the Paramagnetic Meissner Effect (PME) or also called Wohlleben effect are reviewed with the emphasis on the PME exhibited by metallic, s-wave superconductors. The PME was observed in field-cool cooling (FC-C) and field-cool warming (FC-W) m(T)-measurements on Al, Nb, Pb, Ta, in compounds such as, e.g., NbSe2, In-Sn, ZrB12, and others, and also in MgB2, the metallic superconductor with the highest transition temperature. Furthermore, samples with different shapes such as crystals, polycrystals, thin films, bi- and multilayers, nanocomposites, nanowires, mesoscopic objects, and porous materials exhibited the PME. The characteristic features of the PME, found mainly in Nb disks, such as the characteristic temperatures T1 and Tp and the apparative details of the various magnetic measurement techniques applied to observe the PME, are discussed. We also show that PME can be observed with the magnetic field applied parallel and perpendicular to the sample surface, that PME can be removed by abrading the sample surface, and that PME can be introduced or enhanced by irradiation processes. The PME can be observed as well in magnetization loops (MHLs, m(H)) in a narrow temperature window Tp

Increasing and improving the critical transition temperature (TC), current density (JC) and the Meissner effect (HC) of conventional superconductors are the most important problems in superconductivity research, but progress has been slow for many years. In this study, by introducing the p-n junction nanostructured electroluminescent inhomogeneous phase with a red wavelength to realize energy injection, we found the improved property of smart meta-superconductors MgB2, the critical transition temperature TC increases by 0.8 K, the current density JC increases by 37%, and the diamagnetism of the Meissner effect HC also significantly improved, compared with pure MgB2. Compared with the previous yttrium oxide inhomogeneous phase, the p-n junction has a higher luminescence intensity, a longer stable life and simpler external field requirements. The coupling between superconducting electrons and surface plasmon polaritons may be explained by this phenomenon. The realization of smart meta-superconductor by the electroluminescent inhomogeneous phase provides a new way to improve the performance of superconductors. [ABSTRACT FROM AUTHOR]

A series of the nano-sized Mn polycrystalline-substituted MgB2 samples were synthesized by solid-state reaction method with the ratio of Mg1−xMnxB2 (x = 0.00, 0.01, 0.03 ,and 0.05). Mn substitution emerges shifting (002) peak position to higher angles on MgB2 samples. This shows that isovalent Mn2+ is substituted by Mg2+ ions. Randomly oriented grains were obtained in surface morphology. The presence of Mn nanoparticles was observed with energy-dispersive spectrometry analysis. The superconducting transition temperature was significantly suppressed by Mn ions, from 39.28 to 26.60 K. Spin-flip scattering and pair breaking effect arose from the magnetic nature of Mn. Increasing Mn content ratio in the samples caused narrower magnetization versus applied magnetic field loops, without magnetic flux jumping. Self-field critical current density decreased from 260 to 16 kA cm−2 with rising Mn substitution ratio. Scaling behavior of the samples was examined between reduced force (f = F/Fmax) and reduced applied field (h = H/Hmax). Fitting lines showed that pure MgB2 was dominated by normal point pinning mechanism at both lower and higher magnetic fields. However, Mn-substituted MgB2 samples exhibited surface pinning mechanism due to grain refinement. [ABSTRACT FROM AUTHOR]

The article presents a study which explores the Universal Josephson diode effect. It mentions the universal mechanism for the Josephson diode effect in short Josephson junctions. It discusses the scheme for achieving finite-momentum pairing, which does not rely on spin-orbit coupling and thus greatly expands existing platforms for the observation of supercurrent diode effects.

In recent years, the field of flexible electronics has become one of the cross-disciplinary research hotspots, attracting worldwide attention and making rapid advances. So far, there has been plenty of research on the use of two-dimensional (2D) materials in flexible electronics, including graphene, transition metal dichalcogenide, and so on. In this work, we successfully prepared quasi-one-dimensional (Q1D) Nb2Pd0.73S5.97 superconductors on flexible paper by mechanical friction and systematically studied their physical properties at low temperatures. Superconductivity with transition temperature (Tc) ∼ 6.05 K by Meissner effect was observed in Nb2Pd0.73S5.97 wires coated on flexible paper, and a resistance drop at 4.80 K was confirmed in electrical transport measurements. The lower critical field (Hc1) of coated paper shows anisotropy effect under parallel and perpendicular magnetic fields, exhibiting a 2D-like feature, unlike the bulk Nb2Pd0.73S5.97 fibers. Our work provides a broader platform for the application of low-dimensional materials in flexible functional devices. [ABSTRACT FROM AUTHOR]

The temperature dependences of the longitudinal resistance and heat capacity of silicon-carbide epitaxial films grown on single-crystal silicon substrates by the method of ghe coordinated substitution of atoms are investigated. The features in the behavior of these dependences are found at temperatures of 56, 76, 122, and 130°C. The observed features of the behavior of the heat capacity and longitudinal resistance taking into account the appearance of a giant value of diamagnetism previously discovered in samples at these temperatures are interpreted as the phase transitions of charge carriers into a coherent (possibly superconducting if we take into account diamagnetism) state. [ABSTRACT FROM AUTHOR]