Types Of Superconductors Research Articles

Electromagnetic properties and structure of superconducting materials based on AHP-FCE model

Abstract In this paper, the electromagnetic properties and structural characteristics of superconducting materials are studied based on AHP hierarchical analysis and FCE fuzzy comprehensive evaluation method. A sub-analytical model is established using hierarchical analysis and a weight set is established using FCE fuzzy comprehensive evaluation method, respectively, and a comprehensive evaluation model is established to study the average magnetization intensity and vortex of samples with different pore size types and sizes under the same conditions. Then the superconducting current situation at special locations is studied, focusing on summarizing the structural characteristics of most typical superconductors. The number of vortices in the superconducting square tube gradually decreases as the pore size increases. The maximum absolute value of its average magnetization intensity decreases with the increase of the aperture diameter, while its penetrating magnetic field increases subsequently. The superconducting square tube remains in the superconducting state until the magnetic field reaches a certain value. Most of the superconducting material structures are hierarchical crystal structures, such as MgB2, a simple binary and substance of simple hexagonal crystal system, and AlB2 type simple hexagonal structure with theoretical density of 2.605g/cm3 and dot constants of a=30.84nm and c=35.24nm, which belong to the P6/mmm space group. Superconductors not only have zero resistance properties at critical temperature, but also have electromagnetic properties that conventional conductors do not have at all under certain conditions, so it is important to study the properties of superconducting materials.

Fully gapped superconductivity with preserved time-reversal symmetry in NiBi3 single crystals

We report a study of ${\mathrm{NiBi}}_{3}$ single crystals by means of electrical-resistivity, magnetization, and muon-spin rotation and relaxation ($\ensuremath{\mu}\mathrm{SR}$) measurements. As a single crystal, ${\mathrm{NiBi}}_{3}$ adopts a needlelike shape and exhibits bulk superconductivity with ${T}_{c}\ensuremath{\approx}4.1$ K. By applying magnetic fields parallel and perpendicular to the $b$ axis of ${\mathrm{NiBi}}_{3}$, we establish that its lower and upper critical fields as well as the magnetic penetration depths show slightly different values, suggesting a weakly anisotropic superconductivity. In both cases, the zero-temperature upper critical fields are much smaller than the Pauli-limit value, indicating that the superconducting state is constrained by the orbital pair breaking. The temperature evolution of the superfluid density, obtained from transverse-field $\ensuremath{\mu}\mathrm{SR}$, reveals a fully gapped superconductivity in ${\mathrm{NiBi}}_{3}$, with a shared superconducting gap ${\mathrm{\ensuremath{\Delta}}}_{0}=2.1{k}_{\mathrm{B}}{T}_{c}$ and magnetic penetration depths ${\ensuremath{\lambda}}_{0}$ = 223 and 210 nm for $H\ensuremath{\parallel}b$ and $H\ensuremath{\perp}b$, respectively. The lack of spontaneous fields below ${T}_{c}$ indicates that time-reversal symmetry is preserved in ${\mathrm{NiBi}}_{3}$. The absence of a fast muon-spin relaxation and/or precession in the zero-field $\ensuremath{\mu}\mathrm{SR}$ spectra definitely rules out any type of magnetic ordering in ${\mathrm{NiBi}}_{3}$ single crystals. Overall, our investigation suggests that ${\mathrm{NiBi}}_{3}$ behaves as a conventional $s$-type superconductor.

High-entropy silicide superconductors with W5Si3 -type structure

We report the synthesis, crystal structure and physical properties of two new high-entropy silicides (HESs), namely (Nb$_{0.1}$Mo$_{0.3}$W$_{0.3}$Re$_{0.2}$Ru$_{0.1}$)$_{5}$Si$_{3}$ and (Nb$_{0.2}$Mo$_{0.3}$W$_{0.3}$Re$_{0.1}$Ru$_{0.1}$)$_{5}$Si$_{3}$. Structural analysis indicates that both HESs consist of a (nearly) single tetragonal W$_{5}$Si$_{3}$-type phase (space group $I$4/$mcm$) with a disordered cation distribution. Electrical resistivity, magnetic susceptibility and specific heat measurements show that (Nb$_{0.1}$Mo$_{0.3}$W$_{0.3}$Re$_{0.2}$Ru$_{0.1}$)$_{5}$Si$_{3}$ and (Nb$_{0.2}$Mo$_{0.3}$W$_{0.3}$Re$_{0.1}$Ru$_{0.1}$)$_{5}$Si$_{3}$ are weakly coupled bulk superconductors, which represent the first superconducting high-entropy nonoxide ceramics. In particular, these HESs have higher $T_{\rm c}$ values (3.2-3.3 K) compared with those of the binary counterparts, and their $B_{\rm c2}$(0)/$T_{\rm c}$ ratios are the largest among superconductors of the same structural type.

Rigorous formalism for unconventional symmetry breaking in Fermi liquid theory and its application to nematicity in FeSe

Unconventional symmetry breaking due to nonlocal order parameters has attracted considerable attention in many strongly correlated metals. Famous examples are the nematic order in Fe-based superconductors and the star-of-David charge density order in kagome metals. Such exotic symmetry breaking in metals is a central issue of modern condensed matter physics, while its theoretical foundation is still unclear in comparison with the well-established theory of superconductivity. To overcome this difficulty, here we introduce the "form factor" that generalizes the nonlocal order parameter into the Luttinger-Ward (LW) Fermi liquid theory. We then construct a rigorous formalism of the "density-wave equation" that gives the thermodynamically stable form factor, similarly to the superconducting-gap equation. In addition, a rigorous expression of the Ginzburg-Landau free-energy for the unconventional order is presented to calculate various thermodynamic properties. In the next stage, we apply the derived formalism to a typical Fe-based superconductor FeSe, by using the one-loop LW function that represents the free-energy gain due to the interference among paramagnons. The following key experiments are naturally explained: (i) Lifshitz transition (=disappearance of an electron-pocket) due to the bond+orbital order below $T_c$. (ii) Curie-Weiss behavior of the nematic susceptibility at higher T, and the deviation from the Curie-Weiss behavior at lower T near the nematic quantum-critical-point. (iii) Scaling relation of the specific heat jump at $T_c$, $\Delta C/T_c \propto T_c^b$ with $b \sim 3$. (Note that b=0 in the BCS theory.) These results lead to a conclusion that the nematicity in FeSe is the bond+orbital order due to the "paramagnon interference mechanism". The present theory paves the way for solving various unconventional phase transition systems.

First-principles study of physical, and superconducting properties of newly discovered full-Heusler compound MgPd 2 Sb

A DFT-based theoretical technique is used to investigate the physical characteristics of type-II MgPd 2 Sb superconductor, which reveals superconductivity below 2.83 K. By using the McMillan equation, the computed electron-phonon coupling constant is 0.60. This suggests that this compound can be classified as a weakly coupled superconductor, which is consistent in accordance with earlier published theoretical as well as experimental results. The calculated lattice parameter, density of state (DOS) and Debye temperature are also consistent with other studies. The calculated electronic band structure indicates that the studied compound is metallic in nature. For the first time we have investigated the detailed optical and mechanical characteristics of MgPd 2 Sb superconductor. The computed elastic constant reveals that this compound is mechanically stable and ductile. The anisotropy of the MgPd 2 Sb superconductor is determined by using the Zener anisotropic algorithm and the ELATE code.The optical properties of this Heusler type superconductor are nearly similar to other members of the same family. We believe that the present findings can assist researchers in finding and analyzing new superconducting candidates among the full-Heusler alloys.

Superconductivity with large upper critical field in noncentrosymmetric Cr-bearing high-entropy alloys

A series of new Cr5+xMo35−xW12Re35Ru13C20 high-entropy alloys (HEAs) have been synthesized and characterized by x-ray diffraction, scanning electron microscopy, electrical resistivity, magnetic susceptibility and specific heat measurements. It is found that the HEAs adopt a noncentrosymmetric cubic β-Mn type structure and exhibit bulk superconductivity for 0 ≤x≤ 9. With increasing x, the cubic lattice parameter decreases from 6.7940(3) Å to 6.7516(3) Å. Meanwhile, the superconducting transition temperature Tc is suppressed from 5.49 K to 3.35 K due to the magnetic pair breaking caused by Cr moments. For all these noncentrosymmetric HEAs, the zero-temperature upper critical field Bc2(0) is comparable to the Pauli paramagnetic limit BP(0) = 1.86Tc. In particular, the Bc2(0)/BP(0) ratio reaches a maximum of ∼1.03 at x = 6, which is among the highest for β-Mn type superconductors.

Dual Ion Conducting Solid Electrolyte and Electrochemical Protocol for Interface Design

The major challenges for the development of all solid-state batteries (ASSBs), that would be cheaper and can be charged and discharged faster, are stable solid electrolytes and robust interfacial design. We report the dual ion conduction capability of Na-based NASICON type super ion conductor materials using Na1+xMnx/2Zr2-x/2(PO4)3 (NMZP) as a candidate system [1]. This method enables the use of Na-based NASICON material family in both Na as well as Li all solid-state batteries (Figure 1a). The ionic conductivity NZMPs increased as the x value increased and x = 2 showed the highest room temperature conductivities. Crystallographic analysis using neutron diffraction revealed that conductivities observed in these materials are related to the variations in the Na-O bond length and the concentration of mobile sodium content. Using Galvano static plating and stripping tests, we show that these NMZPs boast good cycling stability against both Na and Li metals which also reveals dual ion conduction. Mechanistic investigations through postmortem SEM/EDS and XPS characterizations of the alkali metal and the cycled NMZPs confirm that the Na-Li ion exchange occurs readily in these materials when electrochemically cycled. ASSBs have several interfaces and the interface properties vary depending on the contact condition, energy states, type defects, and chemical/electrochemical stability. ASSB life and performance rely largely on these interfaces since dendrite formation, Li-depleted space-charge layer generation, and spatial variation in interfacial adhesion originate at the interfaces, which leads to battery failure. Stabilizing Li | SE interface is crucial for the development of high-energy-density solid-state batteries. Current approaches in Li metal stabilization employ energy and cost-intensive protocols that have a detrimental impact on the techno-economic feasibility of the ASSBs. This presentation will focus on the facile, electrochemical protocol for improving the interfacial impedance and contact at the Li | Li6.25Al0.25La3Zr2O12 (LALZO) interface. Implementation of a fraction of second short duration high voltage pulse to a poorly formed interface leads to a sustained improvement in contact impedance and lower overpotentials for electrodeposition and electro-dissolution [2] (Figure 1b). This high pulse protocol does not induce the formation of dendrites on the symmetric cells. This electrochemical protocol has direct application in battery formation cycles as well as online management systems for ASSBs. Reference [1]. A. Parejiya, R. Essehli, R. Amin, J. Liu, N. Muralidharan, H. M. Meyer, III, D. L. Wood, III, and I. Belharouak, ACS Energy Letters 6 (2021) 429.[2]. A. Parejiya, R. Amin, M.B. Dixit, R. Essehli, C. Jafta, D.L. Wood, and I. Belharouak., ACS Energy Lett. 6 (2021) 3669. Figure 1

AC Loss Measurement of Double Pancakes Wound With MgB2 Rutherford Type Superconductor

Double pancakes (DPs) for a Superconducting Magnetic Energy Storage (SMES) coil have been developed using MgB <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Rutherford type superconductors. The DPs with 400 mm ID and about 600 mm OD were wound with Rutherford type conductors cabled by twisting multi-filamentary MgB <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> strands. For use in an indirect cooling system, the DPs and thin pure copper sheets as thermal conductors were alternately stacked, and the SMES coil was assembled. In the experiment, while continuous triangular current waveforms up to 600 A and DC current were supplied to two configurations of the SEMS coil, the AC loss at 4.2 K was measured by calorimetric method. By comparing the losses under each excitation and configuration, the AC loss in the SMES coil and an eddy current loss in the copper sheets were obtained, separately. The resultant AC loss in the SMES coil was in agreement with the theoretical values.

Floquet topological superconductivity induced by chiral many-body interaction

Non-equilibrium engineering is becoming a seminal way for realising novel quantum phases that are unimaginable in equilibrium. In particular, Floquet theory applied to quantum mechanics revealed that we can even control the band topology in semimetallic/insulating systems, while the straightforward application to topological superconductivity fails for typical superconductors because the supercondicting gap function does not couple to the electromagnetic field in a direct manner. Here we show that we can overcome this difficulty by taking account of correlation effects. Namely, we study how a d-wave superconductivity is changed when illuminated by circularly-polarised light (CPL) in the repulsive Hubbard model in the strong-coupling regime. We adopt the Floquet formalism for the Gutzwiller-projected effective Hamiltonian with the time-periodic Schrieffer-Wolff transformation. We find that CPL induces a topological superconductivity with a d + id pairing, which arises from the chiral spin coupling and the three-site term generated by the CPL. The latter term remains significant even for low frequencies and low intensities of the CPL. This is clearly reflected in the obtained phase diagram against the laser intensity and temperature for various frequencies red-detuned from the Hubbard U, with the transient dynamics also examined. The phenomenon revealed here can open a novel, dynamical way to induce a topological superconductivity.

Superconductivity and topological properties of MgB2 -type diborides from first principles

The superconductivities and topological properties of ${\mathrm{MgB}}_{2}$-type diborides are investigated by means of first-principles calculations with different exchange-correlation functionals. Functionals with the van der Waals (vdW) correction (such as OptB88-vdW) may predict critical temperature (${T}_{c}$) comparable with experimental results for several ${\mathrm{MgB}}_{2}$-type superconductors, particularly for the pristine ${\mathrm{MgB}}_{2}$ (39.3 vs 39 K). Interestingly, the spin-fluctuation is found to play a significant role in the superconducting behavior of diborides with transition metal elements, and their ${T}_{c}$ can be enhanced monotonically by applying tensile strains. Furthermore, Dirac surface states of $\mathrm{Ta}\phantom{\rule{0.16em}{0ex}}{\mathrm{B}}_{2}$ and ${\mathrm{NbB}}_{2}$ are revealed, suggesting their potential use as topological superconducting materials. This paper provides a useful guideline for ab initio studies of superconductivities and topological properties of vdW layered materials.

DC 차단기의 차단 시간 단축을 위한 초전도 선재 유형에 따른 차단 특성 분석

DC cutoff must be completed within a few ms. Therefore, this paper derives the optimal superconducting wire winding method for efficient current limiting and fast execution of the blocking operation. First, the electromagnetic field characteristics of the superconducting wire according to the winding type were analyzed using the Maxwell program. After that, the EMTDC/PSCAD program was used to analyze the DC blocking performance according to the winding type. Based on the simulation results, as a result of the DC cut-off experiment for each winding type, the spiral type superconductor has a higher resistance rise curve than the helical type, so it is possible to limit the current efficiently by up to 4.01%. In addition, as the magnetic field characteristics are high, the quench of the superconductor operates quickly and the operation time of the circuit breaker is shortened by 0.19 ms, so it can be confirmed that the blocking completion time is also reduced by 0.25 ms.

Effect of vortex annihilation lines on magnetic relaxation in high-temperature superconductors

We show that in superconductors of type II, where Abrikosov vortices with different polarities are present, the areas where they meet and annihilate each other ($B=0$ lines) ``attract'' a significant part of the magnetization current $j$. This leads to redistribution of $j$ over the sample, and as a result, the rate of magnetic relaxation is reduced. This effect is significant in the case of weak dependence of the activation energy $U$ on $j$, particularly for the flux flow ($U=0$) and at early stages of flux creep ($U\ensuremath{\gtrsim}kT$). The slowdown of the relaxation is mostly pronounced in the remanent state, where the $B=0$ lines are located at the edges of the sample. In the case of flux flow, the remanent magnetization decays as $m\ensuremath{\propto}1/t$ instead of the usual ``field-on'' exponential dependence $m\ensuremath{\propto}exp(\ensuremath{-}t/\ensuremath{\tau})$. The effect is important and observable in the magnetization measurements, for instance, in ${\mathrm{La}}_{2\ensuremath{-}x}{\mathrm{Sr}}_{x}{\mathrm{CuO}}_{4}$ crystals and other novel superconducting materials.

Na1+xMnx/2Zr2–x/2(PO4)3 as a Li+ and Na+ Super Ion Conductor for Solid-State Batteries

Here we report dual ion conduction capability of Na-based NASICON type super ion conductor materials using Na1+xMnx/2Zr2–x/2(PO4)3 (NMZP) as a candidate system. This method enables the use of Na-based NASICON material family in both Na as well as Li all solid-state batteries (SSBs). NZMPs with x = 1.5 and x = 2 showed the highest room-temperature conductivities of 2.86 × 10–5 and 2.82 × 10–5 S cm–1, respectively. Crystallographic analysis using neutron diffraction revealed that conductivities observed in these materials are related to the variations in the Na–O bond length and the concentration of mobile sodium content. Using galvanostatic plating and stripping tests, we show that these NMZPs boast good cycling stability against both Na and Li metals, which also reveals dual ion conduction. Mechanistic investigations through post-mortem SEM/EDS and XPS characterizations of the alkali metal and the cycled NMZPs confirm that the Na–Li ion-exchange occurs readily in these materials when electrochemically cycled.

Main Problems of the Theoretical Physics and Artifacts of Local Physics

Shortcomings of the Boltzmann physical kinetics are considered. Boltzmann equation is only plausible equation. The cosequences originated from this fact are considered in the different fields of theoretical physics from the point of view of nonlocal physics. Namely: main principles of nonlocal physics; generalized hydrodynamic equations; magnetic field evolution in the superconductor of the second type; Hubble expansion; special theory of relativity; the problem of the interaction of matter (M) with physical vacuum (PV) is considered including the PV—M energy exchange. Application nonlocal physics to the problem of the dark matter existence—dark matter does not exist, analytical investigation.

Fluctuating Cooper pairs in FeSe at temperatures exceeding double T c

Temperature dependencies of excess conductivity, , have been studied in detail for three FeSe0.94 textured polycrystalline samples prepared by partial melting and solid state reaction. It was revealed that both and its temperature dependence are extremely sensitive to the method of sample preparation. Then, it was shown that in the range from the superconducting transition temperature T c ~9 K up to the characteristic temperature T 01 ~19 K, obeys the classical fluctuation theories of Aslamazov–Larkin (AL) and Hikami-Larkin (Maki-Thompson (MT) term) pointing to the existence of fluctuating Cooper pairs in FeSe at temperatures exceeding double T c . Like in cuprates, AL–MT crossover at is observed, which means the appearance of 3D–2D dimensional transition at this temperature. This allows us to determine the coherence length along the c-axis, ξ c (0) ~3 Å, and a set of additional samples’ parameters, including the phase relaxation time, , of fluctuating Cooper pairs (FCPs), within a simple two-dimensional free-carrier picture. It was shown that in FeSe coincides with that found for YBa2Cu3O suggesting that the nature of superconducting fluctuations is very similar for these high-temperature superconductors of different types.

Current density distribution in resistive fault current limiters and its effect on device stability

The increase of current uniformity along of a Resistive type Superconductor Fault Current Limiter (R-SFCL) in the design of this type of limiters is well perceived as an important issue. The non-uniform distribution of current in R-SFCL only increases the current in some superconducting regions, as a result, in the fault conditions, only certain parts of the superconductor undergo a phase change that increases the heat pressure in those areas and causes the breakdown and destruction of the device. In this paper, the current density distributions in common patterns used in R-SFCs constructions have been simulated and investigated. To this end, an effective model is proposed for R-SFCL to achieve the highest uniformity of current and harmonic phase change over superconductors compared to other patterns. The simulation results in the Ansys Maxwell Software advocate the appropriate and satisfying performance of the proposed model.

Highly Porous Superconductors: Synthesis, Research, and Prospects

This paper gives a review of studies of superconductors with a porosity above 50%. The pores in such superconducting materials provide refrigerant penetration, efficient heat dissipation and stable operation. Methods for the synthesis of the main groups of porous superconductors are described. The results of studies of the structural, magnetic, and electrical transport properties are presented, and the features of the current flow through porous superconductors of various types are considered.

Doping-Induced Superconductivity in the Topological Semimetal Mo5Si3

Chemical doping of topological materials may provide a possible route for realizing topological superconductivity. However, all such cases known so far are based on chalcogenides. Here we report the discovery of superconductivity induced by Re doping in the topological semimetal Mo$_{5}$Si$_{3}$ with a tetragonal structure. Partial substitution of Re for Mo in Mo$_{5-x}$Re$_{x}$Si$_{3}$ results in an anisotropic shrinkage of the unit cell up to the solubility limit of approximately $x$ = 2. Over a wide doping range (0.5 $\leq$ $x$ $\leq$ 2), these silicides are found to be weakly coupled superconductors with a fully isotropic gap. $T_{\rm c}$ increases monotonically with $x$ from 1.67 K to 5.78 K, the latter of which is the highest among superconductors of the same structural type. This trend in $T_{\rm c}$ correlates well with the variation of the number of valence electrons, and is mainly ascribed to the enhancement of electron-phonon coupling. In addition, band structure calculations reveal that superconducting Mo$_{5-x}$Re$_{x}$Si$_{3}$ exhibits nontrivial band topology characterized by $Z_{2}$ invariants (1;000) or (1;111) depending on the Re doping level. Our results suggest that transition metal silicides are a fertile ground for the exploration of candidate topological superconductors.

Collective modes and terahertz near-field response of superconductors

We theoretically study the low energy electromagnetic response of BCS type superconductors focusing on propagating collective modes that are observable with THz near field optics. The interesting frequency and momentum range is $\omega < 2\Delta$ and $q < 1/\xi$ where $\Delta$ is the gap and $\xi$ is the coherence length. We show that it is possible to observe the superfluid plasmons, amplitude (Higgs) modes, Bardasis-Schrieffer modes and Carlson-Goldman modes using THz near field technique, although none of these modes couple linearly to far field radiation. Coupling of THz near field radiation to the amplitude mode requires particle-hole symmetry breaking while coupling to the Bardasis-Schrieffer mode does not and is typically stronger. For parameters appropriate to layered superconductors of current interest, the Carlson-Goldman mode appears in the near field reflection coefficient as a weak feature in the sub-THz frequency range. In a system of two superconducting layers with nanometer scale separation, an acoustic phase mode appears as the antisymmetric density fluctuation mode of the system. This mode produces well defined resonance peaks in the near-field THz response and has strong anticrossings with the Bardasis-Schrieffer and amplitude modes, enhancing their response. In a slab consisting of many layers of quasi-two dimensional superconductors, realized for example in samples of high T$_c$ cuprate compounds, many branches of propagating Josephson plasmon modes are found to couple to the THz near field radiation.

Giant microwave absorption in [formula omitted]- and [formula omitted]- wave superconductors

We discuss a new mechanism of microwave absorption in s- and d-wave superconductors, which arises in the presence of a dc supercurrent in the system. It produces a contribution to the ac conductivity that is proportional to the inelastic quasiparticle relaxation time. This contribution also determines the supercurrent dependence of the conductivity. It may significantly exceed the conventional contribution because in typical superconductors the inelastic relaxation time is several orders of magnitude longer than the elastic one. We show that the aforementioned contribution to the conductivity may be expressed in terms of the single particle density of states in superconductors in the presence of a dc supercurrent. Our results may enable determination of the inelastic relaxation time in superconductors from microwave absorption measurements.