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There are various types of materials that have different levels of electrical conductivity, and one category is known as superconductors or superconducting materials. Superconducting materials are characterized by their complete lack of electrical resistivity. These materials are highly important due to their wide range of applications in electricity transmission, although they do have certain limitations. The Bardeen–Cooper–Schryver theory and the Ginzburg–Landau theory are two significant theories used to explain the nature of superconducting materials. Of particular interest in this study is the Ginzburg–Landau differential equation, which is considered a vital equation in this field. This equation belongs to a class of nonlinear differential equations. Our research focuses on simulating solutions to the Ginzburg–Landau equation under steady-state conditions. We conducted simulations for several superconducting materials, including aluminum, niobium, lead, tin, niobium germanide, niobium tin, vanadium silicate, lead hexa-molybdenum octa-sulfur, magnesium diboride, uranium triplatinum, potassium, barium copper oxide, yttrium, calcium copper oxide, and barium mercury. We define a new parameter of the superconductor conduction materials, which is the periodic parameter of the superconductor. By analyzing the periodic solutions obtained from the Ginzburg–Landau differential equation, we were able to determine the values of the periodic penetration parameters for each material. Notably, monatomic superconducting materials exhibited periodic penetration parameters in the range of tens of micrometers, while tetra- and penta-elements materials had values in the tens of nanometers. Superconducting materials of two or three different elements showed average values for these parameters. These findings provide valuable insights into the characteristics and behavior of various superconducting materials. [ABSTRACT FROM AUTHOR]

In this work, we prepared and studied the physical properties of nickel sulfide (NiS) nanostructure thin films, which were deposited on heated glasses substrates (T = 250°C) using the spray pyrolysis technique (SPT)using different Precursor concentrations of these two solution sources: nickel nitrates hyxahydrate {(Ni(NO3)2.6H2O)=X} and thiourea {(CS(NH2)2)=Y}: {30% [X].70%[Y]}, {33%[X].76% [Y]}&{36% [X]. 63 % [Y]} with fixing the other remaining experimental conditions, and this is to understand more the role of the Precursor concentrations of the solutions on the physical properties of nickel sulfide thin films. The results of X-ray diffraction (DRX) analysis showed that all nickel sulfide (NiS) thin films samples are polycrystalline in a hexagonal phase and have a preferred orientation of (010). The Crystallite size (D) was estimated by The Debye–Scherrer’s relation, ranging from 9.915 nm to 22.148 nm. The emergence of the Ni-S bond corresponding to the frequency 668.563 cm–1 was confirmed by FTIR analysis. On the other hand, the energy of the band gaps varies for samples from 0.87, 0.88 to 0.92 eV. Finally, the Sheet resistance (Rsh) was measured using the four-point method, which it used to determine the conductivity of the samples. [ABSTRACT FROM AUTHOR]

Conventional hard and superhard materials, such as diamond and cubic boron nitride, are attractive for fundamental material science and practical industrial application, but severely limited by their poor electrical conductivity. Therefore, it is desirable to design and fabricate novel materials for superior hardness and conductivity. Herein, a class of hard superconductors in alkali or alkaline‐earth metal (AM) borides, namely AMB7, constituted by a B23 cage with one centered metal atom (Li, Na, K, Mg, Ca, and Sr) is reported, which is the first stable clathrate structure in AMB systems. The theoretical calculations demonstrate that all these pressure‐stabilized clathrate structures can be quenched down to ambient conditions, which provides an essential prerequisite for experimental synthesis at moderate pressures. Among them, the highest hardness and maximum superconducting transition temperature (Tc) value are achieved in SrB7 (25.1 GPa) and MgB7 (29.3 K), respectively. Interestingly, the results show that KB7 simultaneously behaves high hardness (22.5 GPa) and superconducting transition temperature (Tc ≈26.2 K). This study opens up a new way to search and design novel superconductors with favorable mechanical properties under high pressure and high‐temperature conditions. [ABSTRACT FROM AUTHOR]

Electrical conductivity is an important transport response in superconductors, enabling clear signatures of dynamical interactions to be observed. Of primary interest in this paper is to study characteristics of the electron-phonon interaction in weak-coupling Eliashberg theory (Eth), and to note the distinctions with Bardeen-Cooper-Schrieffer (BCS) theory. Recent analysis of weak-coupling Eth has shown that while there are modifications from the BCS results, certain dimensionless ratios are in agreement. Here we show that the conductivities in BCS theory and Eth fundamentally differ, with the latter having an imaginary gap component that damps a divergence. We focus on the dirty limit, and for both BCS theory and Eth we derive expressions for the low-frequency limit of the real conductivity. For Eth specifically, there are two limits to consider, depending on the relative size of the frequency and the imaginary part of the gap. In the case of identically zero frequency, we derive an analytical expression for the nuclear magnetic resonance relaxation rate. Our analysis of the conductivity complements the previous study of the Meissner response and provides a thorough understanding of weak-coupling Eth. Electron-phonon coupling plays a fundamental role in the properties of conventional superconductors and is typically understood using BCS theory. Here, the authors study electron-phonon dynamics in the weak-coupling regime of Eliashberg theory identifying the similarities and differences between the two models in the dirty limit. [ABSTRACT FROM AUTHOR]

The present study appears extensively on the role of diffusion annealing temperature intervals 650–850 °C on electrical conductivity, flux pinning ability, superconducting and crystallinity quality of Cobalt (Co) surface-layered Bi-2212 compounds with experimental tests including dc resistivity, bulk density, X-ray diffraction, critical current density measurements, and theoretical calculations. Experimental findings display that the Co ions may be replaced mostly by bismuth sites in the crystal lattice as a consequence of appropriate cation-vacancy, electron configurations of the outer shell, chemical valence states, and electronegativity of chemical contents in the main composition. The fundamental characteristic features refine considerably with 650 °C annealing temperature due to enhancement of antiferromagnetic spin fluctuations in the clusters of microdomains, re-ordering of Cu–O bonds, stabilization of system, pairing mechanism, modulation of insulating Bi–O double layers, and orbital hybridization mechanisms. Accordingly, bulk Bi-2212 ceramic obtained at optimum annealing temperature exhibits the best conductivity because of a decrease in systematic crystallinity problems and potential grain boundary interaction problems expected in the system. Likewise, the optimum annealing temperature triggers the artificial nucleation regions for 2D discrete pancakelike Abrikosov vortices to decelerate thermal fluxon movements. Moreover, the X-ray diffraction results indicate that optimum Co ions in crystal lattice significantly improve crystal structure quality, grain alignment distributions in c -axis orientation, the extension of high- T c Bi-2223 superconducting phase, and average crystallite size parameters. Additionally, the nucleation activation energy is noticed to reduce with optimum Co ions due to enhancement in the nucleation stability and crystallization temperature values to higher temperature zones. Namely, optimum Co ions easily diffusing into the lattice points support the formation of surface nucleation. In contrast, after a critical value of 650 °C, the characteristic properties mentioned suppress remarkably. In conclusion, the main characteristic features are extensively improved by the optimum diffusion annealing temperature for usage in novel and feasible market areas. [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]

AdS 4 generalized extremal branes are scrutinized in the context of AdS/CFT. Holographic superconductors are studied as dual objects to AdS 4 generalized extremal branes, whose coefficients of response and transport in the dual condensed matter theory are calculated and discussed. The holographic Weyl anomaly is also addressed. The holographic superconductor bound current is shown to be enhanced by the parameter controlling the family of AdS 4 generalized extremal branes, when compared to the standard AdS 4 -Reissner–Nordström black brane results. In the probe limit, the electrical DC conductivity for holographic superconductors with AdS 4 generalized extremal brane dual background is also reported. • Holographic superconductors are studied as dual objects to AdS 4 generalized black branes. • The coefficients of response and transport in the dual condensed matter theory are calculated and discussed. • The electrical DC conductivity for holographic superconductors is reported. [ABSTRACT FROM AUTHOR]

Syntheses of the Y 3 B a 5 C u 8 O 18 ± δ (noted Y-358) +x wt.% TiO2 (x = 0.00, 0.10, 0.30, 0.50 and 0.60 wt%) bulk superconducting material are prepared by the standard solid-state reaction process. Then, systematic electrical conductivity fluctuation in normal and superconducting state analyses on the samples is reported. X-ray diffraction (XRD) and scanning electron microscopy (SEM) are used to systematically assess stage formation and microstructures of the samples. XRD with the Rietveld refinement procedure showed that by cumulating the amount of TiO2 nanoparticle into Y358 substance, the crystal lattice constants altered slightly and the orthorhombicity reduced compared to the pure sample. The impact of TiO2 adding upon the superconducting characteristics with critical temperatures Tc analysis showed that as the inclusion of TiO2 nanoparticles content increases the critical temperatures are enhanced for all of the doped samples. Evaluations of excess conductivity fluctuation were conducted by Aslamazov–Larkin (AL) model. Inside the grains, dimensional fluctuation is depending on the Lawrence–Doniach (LD) temperature named T LD . This parameter ( T LD ) was increased in the mean-field area by rising TiO2 in Y358 substance compared to the non-added sample. However, analysing the excess conductivity based on the AL concept leads to the determination of thermodynamic fluctuation and some parameters values such as the critical temperature (T c z e r o) , coherence length ξ c (0) , super-layer length d, critical magnetic fields B c 1 (0) , B c 2 (0) and critical current density J c (0) . These parameters which are significant by the TiO2 nanoscale doping show that the theory outlined in the chapter "Excess conductivity model" is sufficient to describe our results. [ABSTRACT FROM AUTHOR]

Eggshell is a rich source of calcium that is a dielectric material used for doping in a superconductor. Yttrium calcium barium copper oxide (YxCa1−xBa2Cu3O7) was prepared using the sol-gel process and fired at 900 °C or 1,000 °C. The stoichiometric ratio of the raw materials Y2O3:BaCl2:CuO:CaO was 1:2:3:1 based on the molar mass. The obtained YCaBCO had an orthorhombic crystal structure composed of distorted oxygen-deficient perovskite. The orthorhombic structure was unsymmetrical, providing a substantial increase in the physical electromagnetic properties of the superconductor. The YBCO-900-reference analyzed using an impedance analyzer in the range from 500 Hz to (1 × 106) Hz and at room temperature (27 °C) had the following values for capacitance, electrical conductivity, and dielectric constant ± standard error: 8,286.70 ± 28.49 pF, (3.60 ± 0.01) × 107 S/m, and 1,874.794 ± 6.446, respectively. The YCaBCO-900-eggshell (YxCa1−xBa2Cu3O7) analyzed at 500 Hz at room temperature (27 °C) had high values for capacitance, electrical conductivity, and dielectric constant, namely, 8,540.10 ± 2.00 pF, (1.32 ± 0.00) × 108 S/m, and 1,988.540 ± 0.500, respectively. Furthermore, the YCaBCO-900-eggshell had electrical properties (capacitance, conductivity, and dielectric constant values) higher than those of YCaBCO-900-commercial grade measured under the same conditions. The YCaBCO-900-com grade had capacitance of 8,225.75 ± 0.73 pF, electrical conductivity of (1.40 ± 0.01) × 108 S/m, and dielectric constant of 1,874.59 ± 0.17, respectively. Therefore, eggshell is an alternative dielectric material useful for doping in yttrium barium copper oxide (YBCO) to form YCaBCO, thus causing an increase in its electrical properties. The obtained superconductor is a candidate that could be applied in many industries. [ABSTRACT FROM AUTHOR]

An unconventional superconducting state was recently discovered in uranium ditelluride (UTe2), in which spin-triplet superconductivity emerges from the paramagnetic normal state of a heavy-fermion material. The coexistence of magnetic fluctuations and superconductivity, together with the crystal structure of this material, suggests that a distinctive set of symmetries, magnetic properties, and topology underlie the superconducting state. Here, we report observations of a nonzero polar Kerr effect and of two transitions in the specific heat upon entering the superconducting state, which together suggest that the superconductivity in UTe2 is characterized by a two-component order parameter that breaks time-reversal symmetry. These data place constraints on the symmetries of the order parameter and inform the discussion on the presence of topological superconductivity in UTe2. [ABSTRACT FROM AUTHOR]

Electrical transport of both longitudinal and transverse directions carries rich information. Mobility spectrum analysis (MSA) is capable of extracting charge information from conductivity tensor, including charge types, concentration and mobilities. Using a numerical method based on maximum entropy principle, i.e., maximum entropy mobility spectrum analysis (MEMSA), mobility spectrum for β -type PtBi 2 is studied. Three hole-pockets and two electron-pockets were found, including a small hole pocket with very high mobility, which is very likely corresponding to Dirac Fermions. Benefiting from our high resolution result, we studied temperature dependence of carrier properties and explained the sign change phenomenon of Hall conductivity. We further compared the results with band structure obtained by our first principle calculation. The present results prove MEMSA is a useful tool of extracting carries' information in recently discovered Iron-based superconductors, and topological materials. [ABSTRACT FROM AUTHOR]

This communication reports an electrical magnetoconductivity fluctuation study in polycrystalline (granular) samples of YBa2Cu2.985Fe0.015O $_{\mathrm {7-\delta}}$ and YBa1.75Sr0.25Cu3O $_{\mathrm {7-\delta }}$ superconductors. The measurements were performed in magnetic fields $H \le1000$ Oe applied parallel to the measurement density current. The samples were prepared by a standard solid-state reaction technique. The results were analyzed in terms of the temperature derivative of the electrical resistivity, $d\rho $ /dT, and of the inverse of the logarithmic derivative of the electrical conductivity with respect to temperature, $\chi _{\sigma }^{-1}(T)$. The results allowed the identification of power law divergences of the magnetoconductivity and show that the superconductivity transition in our samples is a two-stage process. The genuine superconductor state with zero resistance stabilizes at the coherence transition temperature, $T_{\mathrm {C0}}$ , in which a long-range-ordered state for the phase of the order parameter is established in the whole granular array. The approach to the zero-resistance state is characterized by the critical exponent $\lambda \sim ~3.5$ for our Sr doped sample and $\lambda \sim ~4$ for our Fe doped sample. It indicates that the universality class for the coherence transition for our samples is that of the 3-D XY model where non-trivial disorder is relevant. At a temperature called $T_{\mathrm {C}}^{\mathrm {IN}}$ ($T_{\mathrm {C}}^{\mathrm {IN}} > T_{\mathrm {C0}}$), we observed another exponent, $\lambda ^{\mathrm {IN}} ~ \sim ~1.4$ , which suggests a crossover in the critical phenomenology dynamic nearby the coherence transition. The origin of this crossover may be related to a change in the universality class of the transition and the value of $\lambda ^{\mathrm {IN}}$ is consistent with a true asymptotic inverted XY critical regime. The chemical doping generally enhances the YBa2Cu3O $_{\mathrm {7-\delta }}$ superconductor granular character; however, its physical contribution to the $\lambda ^{\mathrm {IN}}$ exponent is an open question. [ABSTRACT FROM AUTHOR]

Undoped, Eu- and La-doped CuS nanoparticles stabilized by l-cysteine were synthesized by a low-temperature soft aqueous route. Their structural properties were investigated by X-ray powder diffraction, their morphological properties were scrutinized using scanning electron microscopy, their microstructural properties were carried out using transmission electron microscopy, their optical properties were examined using ultraviolet–visible spectroscopy, and their electrical properties were studied using complex impedance spectroscopy. It was found that Cu0.99La0.01S nanoparticles exhibit the smallest particle size, the highest optical bandgap, the highest values of electrical conductivity and dielectric constant, and the lowest values of dielectric loss tangent when compared with CuS and Cu0.99Eu0.01S nanoparticles. To investigate the effect of the as-synthesized nanoparticles on the superconducting properties of bismuth-based compound ((Bi,Pb)2Sr2Ca2Cu3Oδ), its structural properties were examined by X-ray powder diffraction, its transport properties were analyzed by the standard four-probe technique, its intrinsic properties were investigated using the Aslamazov–Larkin approach and its pinning properties were studied using the thermally activated flux flow model. It was found that Cu0.99La0.01S added sample exhibits the highest Bi-2223 phase concentration, the lowest residual resistivity, the highest critical transition temperature, the lowest value of coherence length, the highest values of penetration depth, upper critical magnetic field and critical current density, the narrowest shift of the zero-resistivity temperature, the highest effective pinning energies and the highest global critical current densities, when compared with pure, CuS and Cu0.99Eu0.01S added samples. [ABSTRACT FROM AUTHOR]

The effect of oxygen annealing on the excess conductivity of Cu0.5Tl0.25M0.25Ba2Ca2Cu3O10-δ (M = K, Na, Li, Tl) samples is investigated. From the analysis of results, we have evaluated the exponents, the coherence length, the crossover temperature, and interlayer coupling strength (J) of the samples. These studies show that the K-doped post-annealed sample has shown narrow transition width with improvement in 2D and 3D conductivities. Oxygen annealing has also enhanced the coherence length and interlayer coupling strength of the material. Na- and Li-doped post-annealed samples have shown increased transition width, poor 2D and 3D conductivities within narrow temperature windows. After annealing, reduction in coherence length and the interlayer coupling strength is also observed. While in Tl-doped sample, oxygen annealing has not caused much deviation in fluctuation induced conductivity (FIC) parameters. The underlying cause of improved behavior of post-annealed K-doped sample is also discussed. [ABSTRACT FROM AUTHOR]

Fe1.01Se0.38Te0.62 single crystal was successfully grown by self-flux method, and effect of post-annealing technique on structure and superconductivity was also systemically studied. The results show the as-grown sample has an excellent superconductivity with an onset transition temperature Tconset ∼ 14.6 K and a zero resistivity temperature Tczero ∼ 13.4 K. After annealing at 400 °C for 48 h, excess Fe in the post-annealing sample appears with Fe1.06Se0.34Te0.66 formula, and superconductivity was strongly suppressed with Tczero ∼ 8.0 K. The experiments found that excess Fe is located at Fe(2) site with local magnetic moment. According to the Werthamer-Helfand-Hohenberg (WHH) theory, the upper critical fields Hc2 at zero temperature were estimated to be 54.2 T for as-grown sample and 28.2 T for post-annealing sample. Two abnormal drops in DC magnetization are found near 40 K and 125 K for all samples, the one near 40 K may be related to a spin freezing of excess Fe and that near 120 K should be corresponding to the structural transition from tetragonal to monoclinic. This is confirmed by the strain measurement. On the other hand, a kink change of specific heat was also found around 10 K for a post-annealed sample. [ABSTRACT FROM AUTHOR]

CuAlS2 has attracted much attention recently as a p-type transparent conductive material. In this paper, we investigate the site preference of substitutional Be in CuAlS2 and the transition level of BeAl using the first-principles calculation. We find that Be would be doped effectively at Al sites in CuAlS2 as a good p-type dopant. In addition, we speculate that Be-Mg or Be-Zn codoped CuAlS2 could have a mobility enhancement and thus a good p-type conductivity due to low lattice distortion. [ABSTRACT FROM AUTHOR]

We investigate the ac Josephson effect in superconductor-graphene-superconductor (SGS) junctions by using the Floquet-Green's function formalism to solve the Dirac-Bogoliubov-de Gennes equation. The numerical results show rich subharmonic gap structures such as the negative differential conductance (NDC) in the dc current. The tunability of the current magnitude can be controlled by the gate voltage, which determines the carriers' densities in graphene. With increasing bias, the ac components decay in an oscillatory manner as in superconductor-normal-superconductor junctions. It is found that the higher-order components have an explicit contribution to the total current under a low bias, which leads to the deviation from a simple sine-like dependence on time for the total current. The NDC characteristics and the tunable current magnitude are excellent hints for the potential application of SGS junctions. [ABSTRACT FROM AUTHOR]

The fluctuation induced conductivity (FIC) of (Cu0.5Tl0.5-xKx)Ba2Ca3Cu4O12-y (x=0,0.25) superconductor has been studied after potassium substitution at thallium site in the charge reservoir layer (Cu0.5Tl0.5Ba2O4-y). The samples were also post-annealed in oxygen to change the carrier density in CuO2 planes. The zero resistivity critical temperature Tc(0) was found to increase after K+1 substitution at Tl+3 sites in the Cu0.5Tl0.5Ba2O4-y charge reservoir layer. However, Tc(0) has been suppressed after post-annealing the samples in oxygen. The FIC analysis was performed in the frame work of Aslamasov-Larkin theory. The results of FIC analysis have shown three-dimensional (3D), two dimensional (2D) and short wavelength fluctuations (SWFs) in the order parameter. It has been also observed that there is an increase in the 3D-2D and 2D-SWF cross-over temperatures after potassium substitution along with an increase in Tc(0). However, after post-annealing in oxygen, the dimensional cross-over has been shifted to lower temperatures. A direct correlation between the cross-over temperatures, the Tc(0) as well as carrier doping level has been observed. [ABSTRACT FROM AUTHOR]

We study the influence of the thickness Df of the plain ferromagnetic (F) film on the electrical resistance of the flux-coupled hybrids, consisting of superconducting (S) Al film and multilayer [Co/Pt] F film with out-of-plain magnetization. The behavior of such hybrids at high and low temperatures is found to be different as follows: the nucleation of superconductivity at high temperatures is governed mainly by the typical lateral dimensions of the magnetic domains, while low-temperature properties are determined by topology of the magnetic template. We show that an increase in the Df value leads to a broadening of the field-intervals and temperature intervals where nonmonotonous dependence of the superconducting critical temperature Tc on the applied magnetic field H is observed (for demagnetized F films). Further increase in the Df value results in a global suppression of superconductivity. Thus, we determined an optimal thickness, when the nonmonotonous dependence Tc(H) can be observed in rather broad T and H range, what can be interesting for further studies of the localized superconductivity in planar Al-based S/F hybrids and for development of the devices which can exploit the localized superconductivity. [ABSTRACT FROM AUTHOR]

We report the enhanced fluctuation-induced conductivity of Be-doped Cu0.5Tl0.5Ba2Ca3-xBex Cu4O12-δ (x=0,0.5,0.75,1.0,1.25,1.5) samples. The analysis has been done with partial substitution of Be in place of Ca. In each case excess conductivity has been analyzed and we tried to make a fit with the Aslamasov–Larkin (AL) and Lawrence–Doniach equations. It is observed that our data fit well with the three-dimensional (3D) AL equation, and a crossover from two dimensions to three dimensions has been found in our samples. We have also employed this transition to estimate the Josephson coupling strength in our samples. This interlayer coupling strength J, which controls the superconducting transition, has been found to improve with increased Be content. The Ginzburg–Landau coherence lengths ξc(0) for all cases have also been calculated. The Fourier transform infrared spectroscopy (FTIR) absorption measurements also provide a clue for the enhanced 3D fluctuations. The higher electronegativity, as well as smaller ionic size, of Be compared to Ca is suggested to be the possible source of promoting enhanced 3D character in Be-doped samples. [ABSTRACT FROM AUTHOR]

We report a study of the microwave conductivity of electron-doped Pr1.85Ce0.15CuO4-δ superconducting thin films using a cavity perturbation technique. The relative frequency shifts obtained for the samples placed at a maximum electric field location in the cavity are treated using the high conductivity limit presented recently by Peligrad et al. [Phys. Rev. B 58, 11652 (1998)].Using two resonance modes, TE102 (16.5 GHz) and TE101 (13 GHz) of the same cavity, only one adjustable parameter Γ is needed to link the frequency shifts of an empty cavity to the ones of a cavity loaded with a perfect conductor. Moreover, by studying different sample configurations, we can relate the substrate effects on the frequency shifts to a scaling factor. These procedures allow us to extract the temperature dependence of the complex penetration depth and the complex microwave conductivity, properties that are highly sensitive on the quality of the films. [ABSTRACT FROM AUTHOR]

The fluctuation-induced conductivity of Ni free and Ni doped Cu0.5Tl0.5Ba2Ca2Cu3-yNiyO10-δ (y=0, 0.5, 1.0, 1.5) samples is investigated for comparison of dimensionality of fluctuations above the mean-field critical temperature. The temperature dependence of paraconductivity can be described by a power law following Aslamazov–Larkin (AL) type equations for these polycrystalline superconductors. It is observed from these studies that at higher temperatures, the fluctuations in the order parameter of the carriers follow two-dimensional (2D) AL behavior, whereas at lower temperatures (closer to transition temperature) their behavior is three-dimensional (3D) AL. From the analysis of our results, we have also evaluated the exponents of dimensionality, the coherence lengths, and the crossover temperatures. The crossover temperature from 2D to 3D have substantially been shifted to lower temperatures with increasing Ni doping, which is most likely related to the scattering of the carriers by remnant spins of Ni atoms. These scattering promote a reduction in the coherence length of the carriers along c-axis. These studies have also shown that the carrier concentration in the conducting CuO2 planes is the most essential; the role of antiferromagnetism in the mechanism of superconductivity is secondary. [ABSTRACT FROM AUTHOR]

We studied the electric transport property of four granular samples RuSr2Gd1.4Ce0.6Cu2O10+δ in different annealing conditions and the results show that the annealing processes gradually destroy the bulk superconductivity with the increase of annealing temperature. However, based on the thermopower and ac susceptibility measurements, the intragranular superconductivity in this Ru-based cuprate is robust as in the other high-Tc superconductors, but the bulk superconductivity is so fragile due to the grain boundary effects. The vanish of bulk superconductivity possibly results from the breaking down of the weak Josephson coupling between grains, as the concentration of oxygens at the grain boundaries decreases during the annealing. [ABSTRACT FROM AUTHOR]

We studied the electric transport property of four granular samples RuSr2Gd1.4Ce0.6Cu2O10+δ in different annealing conditions and the results show that the annealing processes gradually destroy the bulk superconductivity with the increase of annealing temperature. However, based on the thermopower and ac susceptibility measurements, the intragranular superconductivity in this Ru-based cuprate is robust as in the other high-Tc superconductors, but the bulk superconductivity is so fragile due to the grain boundary effects. The vanish of bulk superconductivity possibly results from the breaking down of the weak Josephson coupling between grains, as the concentration of oxygens at the grain boundaries decreases during the annealing. [ABSTRACT FROM AUTHOR]

60-nm-thick Cr-doped SrZrO3 thin films with polycrystalline structure were fabricated on SrRuO3/SrTiO3 (100) substrates at 450 °C by off-axis radio-frequency sputtering. From room temperature current-voltage measurements of Pt/Cr-doped SrZrO3/SrRuO3 structures, reproducible bistable resistive switching behavior was observed. The dominant conduction mechanisms of the high-resistance state were Ohmic conduction in the low-electric-field region and Frenkel-Poole emission in the high-electric-field region, while the low-resistance state fully followed Ohmic conduction. These bulk-limited conduction mechanisms imply that resistive switching phenomena may be related to the conducting path in the SrZrO3:Cr film matrix. In addition, the initial-resistance value of as-deposited SrZrO3:Cr films was much higher than that of the high-resistance state, indicating that the first soft-breakdown behavior (defined as the resistance change from the initial-resistance state of as-deposited film to the low-resistance state) is the forming process which generates the conducting path in the SrZrO3:Cr film matrix. As the set voltage (=switching voltage from the high- to low-resistance state) was increased, both the low-resistance state current and the reset voltage (=switching voltage from the low- to high-resistance state) increased due to the generation of a stronger or higher-density conducting path. We suggest that the mechanism of resistive switching is related to the formation of the conducting path in the SrZrO3:Cr matrix, and that the on-state current is determined by the set voltage which controls the generation of the conducting path. [ABSTRACT FROM AUTHOR]

Superconducting technology is ideal for producing selective and sensitive base-station receive filters for wireless communications. Although superconducting filters improve the performance of wireless communications systems, filter nonlinearities limit their potential applications under real-world operating conditions that involve high-power interfering signals. These limitations are examined numerically and experimentally. The intermodulation response of a minimum-phase filter is found to be largely independent of its topology, and to depend on the bandwidth and the steepness of the amplitude response at the band edge. The effect of the small-signal frequency response on the intermodulation response can be separated from those that depend on resonator geometry and material properties. As a result, the intermodulation performance is quantified by a set of figures of merit that measure the quality of a filter design and the material and resonator properties. [ABSTRACT FROM AUTHOR]

Electron–phonon interaction and electronic thermal conductivity have been investigated in heavily doped silicon at subKelvin temperatures. The heat flow between electron and phonon systems is found to be proportional to T[sup 6]. Utilization of a superconductor–semiconductor–superconductor thermometer enables a precise measurement of electron and substrate temperatures. The electronic thermal conductivity is consistent with the Wiedemann–Franz law. [ABSTRACT FROM AUTHOR]