Phenomenon Of Superconductivity Research Articles

A new physical reservoir using the complex dynamics of electric fields in type-II superconductors containing pinning centers interacting with quantized magnetic flux lines

Reservoir computing, which takes advantage of physical phenomena with nonlinearities, is attracting a lot of attention. Therefore, it is expected to focus on superconductivity, a physical phenomenon with nonlinearities between the output electric field and the input current density. Compared to other physical phenomena used in reservoirs, it is considered that with superconductivity, the nonlinearity can easily be adjusted spatially by pin placement to produce dynamics suitable for reservoirs. The nonlinearity between the electric field generated by the motion of the quantized magnetic flux lines and the input current density was used to perform a reservoir computing task. Three waveform generation tasks, a NARMA2 task and a nonlinear-memory task were performed, and all tasks were generally successful. It was found that the electromagnetic phenomenon in superconductors can be used as a physical reservoir.

Theoretical Investigation of Mechanical and Electronic Properties of Hexagonal BaB2

A comprehensive investigation of the electronic and mechanical properties in the hexagonal BaB2 binary system using state of the art first-principles computational techniques is critical for an in-depth understanding of the fundamental properties unique to this binary system. In this context, we derived elastic constants using the metric-tensor formulation, which allowed us to find important mechanical properties such as Bulk Modulus, Shear Modulus, and Vickers's hardness which are fundamental mechanical quantities. Also, this research includes a detailed analysis of the electronic band structures and a study comparison of Fermi surface topologies. The charge density at the Fermi level (N(EF)), which is very important in superconductivity theories, was found to be 1.43 states/eV.uc. Furthermore, we have explored whether there exists a close relationship between these properties and the superconducting behavior of the BaB2 material. Nevertheless, our calculations unequivocally demonstrate that the information derived from electronic band structures and Fermi surfaces alone is insufficient for a comprehensive explanation of the superconductivity phenomenon observed in such materials.

Prediction of superconductivity in a series of tetragonal transition metal dichalcogenides.

Transition metal dichalcogenides (TMDCs) represent a well-known material family with diverse structural phases and rich electronic properties; they are thus an ideal platform for studying the emergence and exotic phenomenon of superconductivity (SC). Herein, we propose the existence of tetragonal TMDCs with a distorted Lieb (dLieb) lattice structure and the stabilized transition metal disulfides (MS2), including dLieb-ZrS2, dLieb-NbS2, dLieb-MnS2, dLieb-FeS2, dLieb-ReS2, and dLieb-OsS2. Except for semiconducting dLieb-ZrS2 and magnetic dLieb-MnS2, the rest of metallic dLieb-MS2 was found to exhibit intrinsic SC with the transition temperature (TC) ranging from ∼5.4 to ∼13.0 K. The TC of dLieb-ReS2 and dLieb-OsS2 exceeded 10 K and was higher than that of the intrinsic SC in the known metallic TMDCs, which is attributed to the significant phonon-softening enhanced electron-phonon coupling strength. Different from the Ising spin-orbit coupling (SOC) effect in existing non-centrosymmetric TMDCs, the non-magnetic dLieb-MS2 monolayers exhibit the Dresselhaus SOC effect, which is featured by in-plane spin orientations and will give rise to the topological SC under proper conditions. In addition to enriching the structural phases of TMDCs, our work predicts a series of SC candidates with high intrinsic TC and topological non-triviality used for fault-tolerant quantum computation.

Dual properties of dense quark matter with color superconductivity phenomenon

Dual properties of dense quark matter with color superconductivity phenomenon

Relativistic superconductivity in 2D: An example

Recently, we formulated an effective scalar electrodynamics model of relativistic type-II superconductivity. We discussed possible electromagnetic behaviors of superconductivity along the lines of the nonrelativistic Ginzburg–Landau theory. This brief work considers a [Formula: see text]D condensate subjected not only to a homogeneous magnetic field but also to a static radial electric field (polar coordinates). The electric field is regarded to have two components: a central constant field and a Coulomb-like field with “charge” g, where g can take only evenly spaced real numbers. We provide the single-vortex supercurrent density together with its associated magnetic flux density for the ground state of the system. Feasible extensions of this example in [Formula: see text]D curvilinear geometries could explain some superconductivity phenomena which do not occur in planar [Formula: see text]D geometries.

Complex AC Magnetic Susceptibility as a Tool for Exploring Nonlinear Magnetic Phenomena and Pinning Properties in Superconductors.

The versatile AC magnetic susceptibility technique offers a detailed insight into the complex electrodynamic phenomena in superconductors. In the present study, we outline the key effects related to the temperature, AC field amplitude and frequency variations of the fundamental and harmonic components for an investigation of the vortex dynamics in a flux-grown FeSe crystal. By means of higher harmonic (nonlinear) analysis, we have explored certain atypical, asymmetric features in the AC magnetic response. These effects were identified through the detection of an even (second) harmonic and an unusual temperature shift in the odd (third) harmonic, possibly due to the complex interactions related to the composite superconducting/magnetic morphology of the crystal. Using the high-frequency sensitivity of the third harmonic, the basic functional dependencies of the pinning activation energy, as the main mixed state parameter, were determined with the implementation of the Kim-Anderson Arrhenius relation in the framework of the collective creep theory.

Disorder-induced trapping and antitrapping of vortices in type-II superconductors

We study the features of the superconductivity nucleation and vortex configurations in superconductors with modulated disorder. Using the Ginzburg-Landau-type theory with spatially varying diffusion coefficient, we uncover and explain the switching between the vortex-defect attraction to the repulsion upon the increase in the external magnetic field. It is shown that for rather weak applied magnetic fields, a superconducting nucleus localized near the region with the suppressed diffusion coefficient possesses a nonzero vorticity whereas the increase in the magnetic field can lead to a transition into the state with zero winding number. We demonstrate the manifestations of this switching phenomenon in superconductors with a large number of defects by performing numerical simulations of the vortex structures in superconductors with periodic spatial profiles of the diffusion coefficient. The obtained results clarify the physics of the vortex arrangement in several classes of the superconducting materials including one-dimensional superlattices and nanopatterned superconductors with regular arrays of the defects characterized by the increased concentration of nonmagnetic impurities.

Theory of Caroli–de Gennes–Matricon analogs in full-shell hybrid nanowires

Full-shell nanowires are hybrid nanostructures consisting of a semiconducting core encapsulated in an epitaxial superconducting shell. When subject to an external magnetic flux, they exhibit the Little-Parks (LP) phenomenon of flux-modulated superconductivity, an effect connected to the physics of Abrikosov vortex lines in type-II superconductors. We show theoretically that full-shell nanowires can host subgap states that are a variant of the Caroli-de Gennes-Matricon (CdGM) states in vortices. These CdGM analogs are shell-induced Van Hove singularities in core subbands. We elucidate their structure, parameter dependence and behavior in tunneling spectroscopy through a series of models of growing complexity. Using microscopic numerical simulations, we show that CdGM analogs exhibit a characteristic skewness towards higher flux values inside non-zero LP lobes resulting from the interplay of three ingredients. First, the orbital coupling to the field shifts the energy of the CdGM analogs proportionally to the flux and to their generalized angular momentum. Second, CdGM analogs coalesce into degeneracy points at flux values for which their corresponding radial wavefunctions are threaded by an integer multiple of the flux quantum. And third, the average radii of all CdGM-analog wavefunctions inside the core are approximately equal and are controlled by the electrostatic band bending at the core/shell interface. As the average radius moves away from the interface, the degeneracy points shift towards larger fluxes from the center of the LP lobes, causing the skewness. This analysis provides a transparent interpretation of the nanowire spectrum that allows to extract microscopic information by measuring the number and skewness of CdGM analogs. Moreover, it allows to derive an efficient Hamiltonian of the full-shell nanowire in terms of a modified hollow-core model at the average radius.

Tuning superconductivity in highly crystalline Pb1−xBix alloy ultrathin films at atomic level

Achieving highly crystalline superconductors with reduced dimensionality and fine-tuning their superconductivity have been daunting challenges in condensed matter physics. Here, we have successfully grown two-monolayer highly crystalline ${\mathrm{Pb}}_{1\ensuremath{-}x}{\mathrm{Bi}}_{x}$(111) films with controllable Bi concentrations $x$ by molecular beam epitaxy and systematically studied their structural and superconducting properties by scanning tunneling microscopy. We first show that the superconducting transition temperatures of ${\mathrm{Pb}}_{1\ensuremath{-}x}{\mathrm{Bi}}_{x}$ films exhibit a domelike behavior with increasing Bi concentration $x$. Our first-principles calculations reveal that Bi doping can promote the electronic states and the electron-phonon coupling strength at lower $x$ and suppress the electron-phonon coupling strength and superconductivity with largely Bi electronic states when Bi doping increases over a critical ratio. Our findings not only demonstrate a quantum phenomenon of superconductivity in highly crystalline alloyed films but also provide a practical pathway to tune the superconductivity at the atomic level.

Effect of electromagnetic permeability on transition temperature of superconductivity

The description of superconductivity at high-temperature is a problem that has recently been addressed. Transition temperature of superconductivity, [Formula: see text], depends on the lattice structure type, size and room pressure. In super-lattices and low-dimensional layered nanostructures, [Formula: see text] is increased by increasing the complexity of the structure and internal pressures in solid lattice. In this paper, we investigate the relation between physical parameters ([Formula: see text]) of matter and superconductivity properties as well as transition temperature ([Formula: see text]), and explain the superconductivity at high-temperature. In this study, a semi-classical electromagnetic description along with vortex topologic theory and quantum dynamic models with experimental data is considered to justify the relation between superconductivity phenomena and magnetic monopole properties. We find that the electromagnetic energy of magnetic monopole is in agreement with vortex energy in topological theory and it can get close to thermal energy at high-temperature. These models suggest that the superconductivity is related to the mobile monopole or vortices. We show that the electrical permittivity ([Formula: see text]) and magnetic permeability ([Formula: see text]) of matter have a key role in the superconductive properties.

Study of the Properties of YBCO Superconductor Compound in Various Preparation Methods: A Short Review

Superconductors have entered into many applications and advanced technological fields, due to their excellent properties identified by zero resistance and expelling the magnetic field applied to them. Superconductivity is a viable technology to prevent energy losses contributed by electrical resistivity. Also, the magnetic flux is repelled entirely out of the body of superconducting material which makes the Meissner Effect. High-Temperature Superconductors (HTS) have become the focus of researchers and scientists. This is because it uses liquid nitrogen "LN" in cooling, which gives it significant critical temperatures compared to traditional materials based on liquid helium "LHe" in cooling. From this point of view, began to employ these materials in most disciplines and modern technologies. In this article, the phenomenon of Superconductivity will define with explain its most prominent characteristics and focus on the preparation of the HTS (Yttrium-Barium-Copper-Oxide) compound (Abbreviated as YBCO) in different methods "The Sol-Gel and Citrate Pyrolysis Methods", to creating ultrafine superconducting (Y-123) powders. Generally known that by adopting any preparation technique, the superconducting transition temperature (Tc) value of ≈ 92 K could be achieved in the bulk samples. The Citrate Pyrolysis method is a unique route to prepare reactive precursor mixtures through an ignition process of a concentrated aqueous solution including metallic ions of stoichiometric composition. This procedure enables to synthesize of highly homogeneous and fine powders for functional materials, in comparison to the Sol-gel technique.

Classifacation of modern superconductors and their theory based on through experiments conducted on Cuprates

In this article, the physical nature of the phenomenon of superconductivity, related theoretical information and concepts of modern physics regarding the classification of superconductors are covered. The practical importance of the laws of superconductivity physics determined in cuprate superconductors is explained on the basis of the latest scientific innovations.

Study of the High Rotational Bands of Moderately Heavy Nuclei

Abstract: This paper provides a study of the rotational properties of heavy and medium nuclei, particularly the paired nuclei existing in the rare-earth, including Gd, Er, …, first to have a good representation of the intrinsic prolate fundamentals of the considered nuclei. The most important residual nuclear interaction is the pairing force which makes it possible to couple the nucleons in pairs. To take it into account, we introduce the Bardeen-Cooper-Shrie formalism (BCS), developed to describe the phenomenon of superconductivity. The test wave function is then more elaborate than that of Hartree-Fock and corresponds to a state no longer of independent particles, but of independent quasi-particles. A quasi-particle state (qp) is a linear combination of particles and holes. The Routhian Hartree-Fock model through the analysis of the experimental spectra of rotation of the deformed nucleus was usewd. Knowing that this was originally expanded by Bohr-Mottelson by applying I(I+1) expansion, we modified an existing fixed code (HF) with axial symmetry, which extended in a way that allows us to add constraints on the angular momentum and kelvin rotation to the Hamiltonian known as Cr.HF (cranking version of this formalism), initially studied by P. Quentin. This modification led to good results, especially the spectra of rotation and the angular velocities as a function of the angular momentum. Besides, it led to a decrease in the moment of inertia after it was large in some models, such as in the Hartree-Fock-Bogoliubov (HFB) model. The rotational properties and the moments of inertia of the super-deformed bands of some deformed nuclei have been studied as well as in the mass regions A=190; A=160. The results were compared with experimental results which gave good agreement. This work will offer an interesting perspective necessary for certain improvements or extensions of the Cr.HF. Keywords: Microscopic mean field, Collective nuclear rotation, Angular momentum Routhian Hartree-Fock (RHF) model, Inertia moments, Angular velocity.

Simultaneously improving Rashba-type and Zeeman effects in two-dimensional multiferroics

First-principles calculations are performed to investigate Rashba-type and Zeeman effects in two-dimensional three-atom-layer structures $X\mathrm{Te}$/MnTe/$X\mathrm{Te}$ ($XMX, X=\text{Sn}$, Ge). It is found that the Rashba-type and Zeeman effects that typically compete against each other rather cooperatively work together and are improved in $XMX$, as compared to $X\mathrm{Te}/X\mathrm{Te}/X\mathrm{Te}$ ($XXX$). This cooperation and improvement are highly required in Majorana qubits for topological quantum computing, Josephson junction of topological superconductivity, and other phenomena. The Rashba-type effect is improved because replacing $X\mathrm{Te}$ by MnTe leads to a reduction of the thickness of $XMX$ and increases the interaction between the surface state of the lowest conduction bands and its neighboring states. The improved Zeeman effect in the $XMX$ structure arises from s-d and p-d exchange interactions between Te and Mn ions. The present strategy of simultaneously largely improving Rashba-type and Zeeman effects therefore provides a route to realize stable Majorana fermions, topological superconductivity, and other phenomena that require both large Rashba-type and Zeeman effects.

Exploring two-dimensional van der Waals heavy-fermion material: Data mining theoretical approach

The discovery of two-dimensional (2D) van der Waals (vdW) materials often provides interesting playgrounds to explore novel phenomena. One of the missing components in 2D vdW materials is the intrinsic heavy-fermion systems, which can provide an additional degree of freedom to study quantum critical point (QCP), unconventional superconductivity, and emergent phenomena in vdW heterostructures. Here, we investigate 2D vdW heavy-fermion candidates through the database of experimentally known compounds based on dynamical mean-field theory calculation combined with density functional theory (DFT+DMFT). We have found that the Kondo resonance state of CeSiI does not change upon exfoliation and can be easily controlled by strain and surface doping. Our result indicates that CeSiI is an ideal 2D vdW heavy-fermion material and the quantum critical point can be identified by external perturbations.

Interactions between Fermi polarons in monolayer WS2

Interactions between quasiparticles are of fundamental importance and ultimately determine the macroscopic properties of quantum matter. A famous example is the phenomenon of superconductivity, which arises from attractive electron-electron interactions that are mediated by phonons or even other more exotic fluctuations in the material. Here we introduce mobile exciton impurities into a two-dimensional electron gas and investigate the interactions between the resulting Fermi polaron quasiparticles. We employ multi-dimensional coherent spectroscopy on monolayer WS2, which provides an ideal platform for determining the nature of polaron-polaron interactions due to the underlying trion fine structure and the valley specific optical selection rules. At low electron doping densities, we find that the dominant interactions are between polaron states that are dressed by the same Fermi sea. In the absence of bound polaron pairs (bipolarons), we show using a minimal microscopic model that these interactions originate from a phase-space filling effect, where excitons compete for the same electrons. We furthermore reveal the existence of a bipolaron bound state with remarkably large binding energy, involving excitons in different valleys cooperatively bound to the same electron. Our work lays the foundation for probing and understanding strong electron correlation effects in two-dimensional layered structures such as moiré superlattices.

APPLICATION OF THE METHODS OF THE INTEGER THEORY IN PHYSICS

The article discusses the results of solving two classical problems of physics and their consequences - the problem of radiation of a hydrogen-like atom and the problem of scattering - by the mathematical method of the integer theory. The transition to the formulation of these problems in terms of the integer theory became possible as a result of the formulation of the hypothesis that, during the interaction of physical objects, the exchange of quantities that are conserved occurs in such a way that the conserved quantities have a common measure before and after the interaction (i.e., they are commensurable). The concept of magnitude and unit of measure for bound and free objects is discussed. The introduction of the concept of commensurability made it possible to give physical grounds for “allowed” states in quantum physics and to explain the physics of the previously inexplicable requirement that the Miller numbers-index representing crystallographic planes must be coprime. Physical calculations using the mathematics of integers make it possible to predict a number of important consequences in solving applied problems, in particular, in the physics of the phenomenon of superconductivity. Attention is drawn to the fact that the development of science needs the emergence of new ideas and the conductor of such ideas should be philosophy.

Unconventional superconductivity after the BCS paradigm and empirical rules for the exploration of high temperature superconductors

Superconducting state is achieved through quantum condensation of Cooper pairs which are new types of charge carriers other than single electrons in normal metals. The theory established by Bardeen-Cooper-Schrieffer (BCS) in 1957 can successfully explain the phenomenon of superconductivity in many single-element and alloy superconductors. Within the BCS scheme, the Cooper pairs are formed by exchanging the virtual vibrations of lattice (phonons) between two electrons with opposite momentum near the Fermi surface. The BCS theory has dominated the field of superconductivity over 64 years. Many superconductors discovered in past four decades, such as the heavy Fermion superconductors, cuprates, iron pnictide/chalcogenide and nickelates seem, however, to strongly violate the BCS picture. The most important issue is that, perhaps the BCS picture based on electron-phonon coupling are the special case for superconductivity, there are a lot of other reasons or routes for the Cooper pairing and superconductivity. In this short overview paper, we will summarize part of these progresses and try to guide readers to some new possible schemes of superconductivity after the BCS paradigm. We also propose several empirical rules for the exploration of high-temperature unconventional superconductors.

Theoretical exploration of external pressure impact on superconducting transition temperatures

An external pressure could raise superconducting transition temperatures Tc, which has been experimentally observed but hasn’t been understood systematically. Utilizing superconducting transition temperature equations obtained with Eyring’s rate process theory and free volume concept in our previous work, we have explored how an externally applied pressure could change Tc in this article, under an assumption that the pressure P could change the free volume available for electrons in a system. The electron traveling distance and/or inter-particle spacing between electrons could have a linear, power law, and exponential relationships with pressures, borrowed from the relationship between viscosity and the free volume of molecules for glass liquids. Predicted relationships between Tc and pressures can be used to explain currently observed experimental phenomena such as Tc linearly increasing with pressures, initially slowly increasing and then suddenly jumping to a very high level, or showing skewed saw tooth relationships, etc. Our findings may provide an alternative simple theoretical approach to understand pressure induced superconductivity phenomena, further clearing doubts on many seemingly unrelated experimental observations.

Plasma and Superconductivity for the Sustainable Development of Energy and the Environment

The main aim of this review is to present the current state of the research and applications of superconductivity and plasma technologies in the field of energy and environmental protection. An additional goal is to attract the attention of specialists, university students and readers interested in the state of energy and the natural environment and in how to protect them and ensure their sustainable development. Modern energy systems and the natural environment do not develop in a sustainable manner, thus providing future generations with access to energy that is generated from renewable sources and that does not degrade the natural environment. Most of the energy technologies used today are based on non-renewable sources. Power contained in fuel is irretrievably lost, and the quality of the energy is lowered. It is accompanied by the emissions of fossil fuel combustion products into the atmosphere, which pollutes the natural environment. Environmental problems, such as the production of gaseous and solid pollutants and their emission into the atmosphere, climate change, ozone depletion and acid rains, are discussed. For the problem of air pollution, the effects of combustion products in the form of carbon oxides, sulfur and nitrogen compounds are analyzed. The plasma and superconductivity phenomena, as well as their most important parameters, properties and classifications, are reviewed. In the case of atmospheric pressure plasma generation, basic information about technological gas composition, pressure, discharge type, electromagnetic field specification, electrode geometry, voltage supply systems, etc., are presented. For the phenomenon of superconductivity, attention is mainly paid to the interdependencies between Tc, magnetic flux density Bc and current density Jc parameters. Plasma technologies and superconductivity can offer innovative and energy-saving solutions for power engineering and environmental problems through decreasing the effects of energy production, conversion and distribution for the environment and by reductions in power losses and counteracting energy quality degradation. This paper presents an overview of the application of technologies using plasma and superconductivity phenomena in power engineering and in environmental protection processes. This review of plasma technologies, related to reductions in greenhouse gas emissions and the transformation and valorization of industrial waste for applications in energy and environmental engineering, is carried out. In particular, the most plasma-based approaches for carbon oxides, sulfur and nitrogen compounds removal are discussed. The most common plasma reactors used in fuel reforming technologies, such as dielectric barrier discharge, microwave discharge and gliding-arc discharge, are described. The advantages of solid waste treatment using plasma arc techniques are introduced. Applications of superconductors for energy generation, conversion and transmission can be divided into two main groups with respect to the conducted current (DC and AC) and into three groups with respect to the employed property (zero resistivity, ideal magnetism/flux trapping and quench transition). Among the superconductivity applications of electrical machines, devices for improving energy quality and storage and high field generation are described. An example that combines the phenomena of hot plasma and superconductivity is thermonuclear fusion. It is a hope for solving the world’s energy problems and for creating a virtually inexhaustible, sustainable and waste-free source of energy for many future generations.