Showing papers on "High-temperature superconductivity published in 2003"
TL;DR: A post-fabrication treatment is presented that improves the mechanical properties as well as thermal conductivity of a bulk Y-Ba-Cu-O magnet, thereby increasing its field-trapping capacity and thermal stability and internal mechanical strength.
Abstract: Large-grain high-temperature superconductors of the form RE-Ba-Cu-O (where RE is a rare-earth element) can trap magnetic fields of several tesla at low temperatures, and so can be used for permanent magnet applications. The magnitude of the trapped field is proportional to the critical current density and the volume of the superconductor. Various potential engineering applications for such magnets have emerged, and some have already been commercialized. However, the range of applications is limited by poor mechanical stability and low thermal conductivity of the bulk superconductors; RE-Ba-Cu-O magnets have been found to fracture during high-field activation, owing to magnetic pressure. Here we present a post-fabrication treatment that improves the mechanical properties as well as thermal conductivity of a bulk Y-Ba-Cu-O magnet, thereby increasing its field-trapping capacity. First, resin impregnation and wrapping the materials in carbon fibre improves the mechanical properties. Second, a small hole drilled into the centre of the magnet allows impregnation of Bi-Pb-Sn-Cd alloy into the superconductor and inclusion of an aluminium wire support, which results in a significant enhancement of thermal stability and internal mechanical strength. As a result, 17.24 T could be trapped, without fracturing, in a bulk Y-Ba-Cu-O sample of 2.65 cm diameter at 29 K.
831 citations
TL;DR: Doping dependence might be a general feature of these materials, but it is found that the low-energy Fermi velocity of electrons is in fact universal, even among different superconductor families.
Abstract: The mechanism that causes high-temperature superconductivity in copper oxide materials (cuprates) is still unknown, more than 15 years after it was discovered1. As the charge carriers (electrons or holes) are introduced into the parent antiferromagnetic insulator, a process called doping, the material evolves from an insulator to a superconductor, and eventually to a normal metal. This marked change of physical properties with doping2,3,4,5,6,7 indicates that doping dependence (non-universality) might be a general feature of these materials, but we find that, on the contrary, the low-energy Fermi velocity of electrons is in fact universal, even among different superconductor families.
228 citations
TL;DR: In this paper, second-phase, nanoscale inclusions of composition Y2Ba4CuMOy (M=U, Nb, Ta, W, Mo, and Re), which form artificial pinning centers, have been introduced into large, single-grain [rare-earth (RE)]-Ba-Cu-O superconductors.
Abstract: Second-phase, nanoscale inclusions of composition Y2Ba4CuMOy (M=U, Nb, Ta, W, Mo, and Re), which form artificial pinning centers, have been introduced into large, single-grain [rare-earth (RE)]-Ba-Cu-O superconductors. A significant improvement in critical current density is observed in these samples, due presumably to various combinations of normal conducting, paramagnetic, and geometrical properties of the Y2Ba4CuMOy particles in the superconducting (RE)Ba2Cu3O7−δ (RE-123) phase matrix. These Y2Ba4CuMOy phase particles are chemically stable in the Ba-Cu-O liquid during peritectic solidification, unlike Y2BaCuO5 (Y-211) phase particles in Y-Ba-Cu-O, which opens a processing window for the fabrication of nanostructured large, single-grain (RE)-Ba-Cu-O superconductors with enhanced flux pinning for high-field engineering applications.
104 citations
TL;DR: In this paper, the authors theoretically demonstrate the tunability of two-dimensional photonic crystals composed of copper oxide high-temperature superconductors (HTSCs), which are composed of rods whose axes are parallel to the c axes in the copper oxide HTSC.
Abstract: We theoretically demonstrate the tunability of two-dimensional photonic crystals composed of copper oxide high-temperature superconductors (HTSCs). The photonic crystals we deal with are composed of rods whose axes are parallel to the c axes in the copper oxide HTSC. Photonic crystals composed of copper oxide HTSCs exhibit the large tunabilities by temperature and magnetic fields. That is, a photonic band gap increases and a midgap frequency decreases with increasing temperature and the magnetic field. Their characteristics are due to the temperature dependence of London penetration depths and the magnetic field dependence of the critical temperature and the London penetration depths. The frequency range in which the photonic band gap appears are strongly dependent on materials in the copper oxide HTSCs.
90 citations
TL;DR: The existence of a second order parameter hidden within the superconducting phase of the underdoped and newly synthesized electron-doped material La2-xCexCuO4-y supports the picture that the physics of high-Tc superconductors is determined by the interplay between competing and coexisting ground states.
Abstract: The ground state of superconductors is characterized by the long-range order of condensed Cooper pairs: this is the only order present in conventional superconductors. The high-transition-temperature (high-T(c)) superconductors, in contrast, exhibit more complex phase behaviour, which might indicate the presence of other competing ground states. For example, the pseudogap--a suppression of the accessible electronic states at the Fermi level in the normal state of high-T(c) superconductors-has been interpreted as either a precursor to superconductivity or as tracer of a nearby ground state that can be separated from the superconducting state by a quantum critical point. Here we report the existence of a second order parameter hidden within the superconducting phase of the underdoped (electron-doped) high-T(c) superconductor Pr2-xCe(x)CuO4-y and the newly synthesized electron-doped material La2-xCe(x)CuO4-y (ref. 8). The existence of a pseudogap when superconductivity is suppressed excludes precursor superconductivity as its origin. Our observation is consistent with the presence of a (quantum) phase transition at T = 0, which may be a key to understanding high-T(c) superconductivity. This supports the picture that the physics of high-T(c) superconductors is determined by the interplay between competing and coexisting ground states.
89 citations
TL;DR: In this article, an overview of recent Raman scattering measurements in metals under conditions of high static pressure in the diamond anvil cell is presented, and the practical improvements of the traditional technique that have made these measurements possible.
Abstract: An overview is presented of recent Raman scattering measurements in metals under conditions of high static pressure in the diamond anvil cell. Also discussed are the practical improvements of the traditional technique that have made these measurements possible. We present the results of several studies including those of hexagonal close-packed (hcp) e-Fe and its solid solutions Fe(1−x)Nix (x ≤ 0.2) over a wide temperature range, and also of high-temperature superconductors (YBCO) and their prototypes, i.e. materials with strong electronic correlations such as the 3d metal oxides CoO and FeO. Copyright © 2003 John Wiley & Sons, Ltd.
82 citations
TL;DR: Angle resolved photoemission spectroscopy (ARPES) and resistivity measurements are used to explore the overdoped region of the high temperature superconductor Bi(2)Sr( 2)CaCu(2]O(8+delta) and find evidence for a new crossover line in the phase diagram.
Abstract: Angle resolved photoemission spectroscopy (ARPES) and resistivity measurements are used to explore the overdoped region of the high temperature superconductor Bi(2)Sr(2)CaCu(2)O(8+delta). We find evidence for a new crossover line in the phase diagram between a coherent metal phase, for lower temperatures and higher doping, and an incoherent metal phase, for higher temperatures and lower doping. The former is characterized by two well-defined spectral peaks in ARPES due to coherent bilayer splitting and superlinear behavior in the resistivity, whereas the latter is characterized by a single broad spectral feature in ARPES and a linear temperature dependence of the resistivity.
67 citations
TL;DR: In this paper, the magnetic flux of vortices in a ferromagnet-superconductor bilayer consisting of CoPt grown on YBCO was demonstrated to improve the critical current at temperatures close to the transition temperature.
Abstract: Flux pinning in high-temperature superconductors such as YBa2Cu3O7−x (YBCO) in the past has been accomplished by pinning the vortex cores. We demonstrate magnetic-domain-induced flux pinning of the magnetic flux of vortices in a ferromagnet-superconductor bilayer consisting of CoPt grown on YBCO, where the ferromagnet has uniaxial perpendicular magnetic anisotropy and a random domain structure. We observe an improvement of the critical current due to magnetic pinning at temperatures close to the transition temperature.
66 citations
TL;DR: In this paper, the authors present a technique for the investigation of local variations of the critical current density in large bulk superconductors, where the sample is not magnetized as a whole before the scan, but locally by a small permanent magnet, which is fixed near the Hall probe, during the scanning process.
Abstract: We present a novel technique for the investigation of local variations of the critical current density in large bulk superconductors. In contrast to the usual Hall probe scanning technique, the sample is not magnetized as a whole before the scan, but locally by a small permanent magnet, which is fixed near the Hall probe, during the scanning process. The resulting signal can be interpreted as a qualitative measure of the local shielding currents flowing at the surface.
62 citations
TL;DR: A new type of broadband measurement of microwave surface resistance that finally shows some of the spectral features expected for a d(x2-y2) pairing state, consistent with weak impurity scattering of nodal quasiparticles is presented.
Abstract: There has long been a discrepancy between microwave conductivity measurements in high temperature superconductors and the conductivity spectrum expected in the simplest models for impurity scattering in a d-wave superconductor. Here we present a new type of broadband measurement of microwave surface resistance that finally shows some of the spectral features expected for a d x 2- y 2 pairing state. Cusp-shaped conductivity spectra, consistent with weak impurity scattering of nodal quasiparticles, were obtained in the 0.6-21 GHz frequency range in highly ordered crystals of YBa 2 CU 3 O 6 . 5 0 and YBa 2 Cu 3 O 6 . 9 9 .
60 citations
TL;DR: In this paper, it was shown that at weak to intermediate coupling, antiferromagnetic fluctuations enhance d-wave pairing correlations until, as one moves closer to half-filling, the antifromagnetic induced pseudogap begins to suppress the tendency to superconductivity.
Abstract: We show that, at weak to intermediate coupling, antiferromagnetic fluctuations enhance d-wave pairing correlations until, as one moves closer to half-filling, the antiferromagnetically induced pseudogap begins to suppress the tendency to superconductivity. The accuracy of our approach is gauged by detailed comparisons with quantum Monte Carlo simulations. The negative pressure dependence of ${T}_{c}$ and the existence of photoemission hot spots in electron-doped cuprate superconductors find their natural explanation within this approach.
TL;DR: In this paper, the authors derived an analytical expression for J as a function of E, T, B, and θ, which can describe and extrapolate the nonlinear E − J characteristics even in extremely low E region and/or high B region based on rather simple measurements.
Abstract: The author’s recent studies on the critical current properties in Bi-2223 multifilamentary tapes as well as YBCO coated IBAD tapes have been reviewed. Extended electric field vs. current density ( E – J ) characteristics were studied over wide range of temperature, T , magnetic field, B , and angle, θ . Based on the analysis of statistic J c distribution and scaling, we derived an analytical expression for J as a function of E , T , B , and θ . This method allows us to describe and extrapolate the nonlinear E – J characteristics even in extremely low E region and/or high B region based on rather simple measurements.
TL;DR: In this paper, angle-resolved photo-emission spectroscopy reveals very surprising strain-induced effects on the electronic band dispersion of epitaxial La2-xSrxCuO4-delta thin films.
Abstract: Angle-resolved photoemission spectroscopy reveals very surprising strain-induced effects on the electronic band dispersion of epitaxial La2-xSrxCuO4-delta thin films. In strained films we measure a band that crosses the Fermi level (E-F) well before the Brillouin zone boundary. This is in contrast to the flat band reported in unstrained single crystals and in our unstrained films, as well as in contrast to the band flattening predicted by band structure calculations for in-plane compressive strain. In spite of the density of states reduction near E-F, the critical temperature increases in strained films with respect to unstrained samples. These results require a radical departure from commonly accepted notions about strain effects on high temperature superconductors, with possible general repercussions on superconductivity theory.
TL;DR: In this article, a face-to-face type superconducting bulk magnet system was applied to the high gradient magnetic separation (HGMS) in which a pair of bulk superconductors were oppositely arranged, and a magnetic field of 1.6 T was achieved between the magnetic poles.
Abstract: Our research is to magnetize the high-T/sub c/ bulk superconductors and to supply magnetic field environment realized by superconducting bulk magnets to various applications. In this paper, we aim to apply the superconducting bulk magnets to the high gradient magnetic separation (HGMS). Using a face-to-face type superconducting bulk magnet system in which a pair of bulk superconductors are oppositely arranged, Y123 bulk superconductors are magnetized by the "IMRA" method (pulsed field magnetization), and consequently, a magnetic field of 1.6 T is achieved between the magnetic poles. Next, HGMS using superconducting bulk magnets is demonstrated. A separation pipe into which filter matrices composed by ferromagnetic wires are stuffed is set between the magnetic poles and the slurry mixed with fine powder of /spl alpha/-hematite (Fe/sub 2/O/sub 3/) particles is flown. As the results of HGMS, over 90% of the Fe/sub 2/O/sub 3/ was separated. Moreover, separation filters have to be washed so that they are not clogged with captured particles. We confirmed that the filter was briefly washed by flowing water after moving the separation pipe from magnetic poles.
TL;DR: In this paper, the generic scaling law has been found to hold for all the HTSC systems examined, i.e., Hirr[Oe]=4×107γ−2 (1−T/Tc)1.5 at T≥0.7Tc.
Abstract: Systematic studies on the irreversibility field Hirr, and anisotropy factor γ2 of high temperature superconductors (HTSC) were performed using single crystals with high quality. The generic scaling law have been found to hold for all the HTSC systems examined, i.e., Hirr[Oe]=4×107γ−2 (1−T/Tc)1.5 at T≥0.7Tc. In addition, γ of each HTSC material is roughly expressed as γ2=2 exp(0.78d[A]) at the carrier optimally-doped state. Based on the “generic” scaling law, the behaviors of the variously doped superconductors, such as Bi(Pb)2212 and Hg(Re)1223, are discussed in terms of the critical current.
TL;DR: In this paper, the electrostatic modulation of superconductivity in very thin films of cuprate superconductors using a field effect device based on a SrTiO3 single-crystal gate insulator was reported.
Abstract: We report on the electrostatic modulation of superconductivity in very thin films of cuprate superconductors using a field-effect device based on a SrTiO3 single-crystal gate insulator A Tc modulation of 35 K and a 37% change of the normal state resistance have been observed in an epitaxial bilayer composed of an insulating PrBa2Cu3O7−δ layer deposited on top of a superconducting NdBa2Cu3O7−δ film, two unit cells thick To achieve large electric fields, the thickness of the commercial dielectric single-crystal SrTiO3 substrate (also used as the gate insulator) was reduced to 110 μm The dielectric properties of the gate insulator were characterized as a function of temperature and electric field and the magnitude of the field effect was quantified A Tc enhancement of 28 K was obtained for an applied field of −18×106 V/m, corresponding to a polarization of −4 μC/cm2
TL;DR: In this article, high quality melt-processed GdBa2Cu3O7−δ, (Sm 0.5Eu0.33Gd0.5)Ba2C7O7+δ single domains were grown in air and the microstructural origin of their distinguished superconducting performance was investigated by a transmission electron microscope equipped with energy-dispersive spectroscopy.
Abstract: High quality melt-processed GdBa2Cu3O7−δ, (Sm0.5Eu0.5)Ba2Cu3O7−δ and (Sm0.33Eu0.33Gd0.33)Ba2Cu3O7−δ single domains were grown in air and the microstructural origin of their distinguished superconducting performance was investigated by a transmission electron microscope equipped with energy-dispersive spectroscopy. A periodic array of the chemical composition with tens of micrometer correlation was unveiled due to the spatial oscillation of RE (RE: Sm, Eu, and Gd) and Ba around the stoichiometric ratio with a nanometer scale wavelength. For (Sm0.5Eu0.5)Ba2Cu3O7−δ, the temperature dependence of the reversible magnetic moment at certain fields showed two kinks. The first transition followed three-dimensional scaling and yielded dBc2/dT=1.98 T/K, corresponding to thermal fluctuation of the bulk superconductivity while the second displayed a linear temperature function with slightly lower Tc than bulk Tc and a slope of 0.6 T/K. This may indicate a field-induced pinning scenario with low Tc stripes.
TL;DR: In this article, the authors proposed an inductive method to measure critical current density Jc in bulk superconductors, where an ac magnetic field is generated by a drive current I0 flowing in a small coil mounted just above the flat surface of supercondors, and the thirdharmonic voltage V3 induced in the coil is detected.
Abstract: We propose an inductive method to measure critical current density Jc in bulk superconductors. In this method, an ac magnetic field is generated by a drive current I0 flowing in a small coil mounted just above the flat surface of superconductors, and the third-harmonic voltage V3 induced in the coil is detected. We present theoretical calculation based on the critical state model for the ac response of bulk superconductors, and we show that the third-harmonic voltage detected in the inductive measurements is expressed as V3=G3ωI02/Jc, where ω/2π is the frequency of the drive current, and G3 is a factor determined by the configuration of the coil. We measured the I0–V3 curves of a melt-textured YBa2Cu3O7−δ bulk sample, and evaluated the Jc by using the theoretical results.
TL;DR: In this paper, the authors show that the zero-bias conductance peak (ZBCP) is comprised of quasiparticle Andreev bound states (ABS), which arise from reflection symmetry breaking at the interface of a superconductor whose superconducting order parameter exhibits d-wave symmetry.
Abstract: Quasiparticle planar tunneling spectroscopy is shown to be a powerful, phase-sensitive spectroscopic tool for the study of unconventional superconductivity. Several familiar and novel junction fabrication techniques on YBa 2 Cu 3 O 7 (YBCO) thin films and Bi 2 Sr 2 CaCu 2 O 8 (BSCCO) single crystals are used for our systematic studies of the tunneling conductances, which are obtained as a function of crystallographic orientation, applied magnetic field (magnitude and orientation) atomic substitution and surface damage. All these results confirm that the observed zero-bias conductance peak (ZBCP) is comprised of quasiparticle (QP) Andreev bound states (ABS), which arise from reflection-symmetry breaking at the interface of a superconductor whose superconducting order parameter (OP) exhibits d-wave, or d x 2 – y 2 , symmetry. Consistency in the observation of the splitting of the ZBCP is presented: The splitting of the ZBCP observed in applied field, and the spontaneous splitting observed at lower temperatures in zero field, occur concomitantly in a given junction, and that observation of this splitting is dependent upon the length-scale of the surface disorder and the magnitude of the tunneling cone, φ .
TL;DR: In this article, the authors studied the levitation forces of YBaCuO bulk HTSs with different shape and size over a NdFeB guideway and found that the shape and the size of the HTS sample had a large influence on its levitation force.
Abstract: Levitation forces of YBaCuO bulk high temperature superconductors (HTS) with different shape and size over a NdFeB guideway were studied. Here, the concentrating magnetic field of the NdFeB guideway was 1.2 T, and the YBaCuO bulk HTSs include three cylindrical samples with different diameter and thickness and one hexagonal sample. The maximum levitation force is as high as 85.3 N at a gap of 5 mm between the bottom surface of YBaCuO bulk HTS and the top surface of the NdFeB guideway, where the applied magnetic field is about 0.8 T. The results show that the shape and the size have large influences on the levitation force of YBaCuO bulk HTSs.
TL;DR: In this article, the authors review the contribution of infrared spectroscopy to the study of the pseudogap in high temperature superconductors and provide evidence that the scattering mode is present in all high temperature cuprates and that its frequency in optimally doped materials scales with the superconducting transition temperature.
TL;DR: In this article, the authors review the contribution of infrared spectroscopy to the study of the pseudogap in high temperature superconductors, which appears as a depression of the frequency dependent conductivity in the c-axis direction and seems to be related to a real gap in the density of states.
Abstract: We review the contribution of infrared spectroscopy to the study of the pseudogap in high temperature superconductors. The pseudogap appears as a depression of the frequency dependent conductivity in the c-axis direction and seems to be related to a real gap in the density of states. It can also be seen in the Knight shift, photoemission and tunneling experiments. In underdoped samples it appears near room temperature and does not close with temperature. Another related phenomenon that has been studied by infrared is the depression in the ab-plane scattering rate. Two separate effects can be discerned. At high temperatures there is broad depression of scattering below 1000 cm-1 which may be related to the gap in the density of states. At a lower temperature a sharper structure is seen, which appears to be associated with scattering from a mode at 300 cm-1, and which governs the carrier life time at low temperatures. This mode shows up in a number of other experiments, as a kink in ARPES dispersion, and a resonance at 41 meV in magnetic neutron scattering. Since the infrared technique can be used on a wide range of samples it has provided evidence that the scattering mode is present in all high temperature cuprates and that its frequency in optimally doped materials scales with the superconducting transition temperature. The lanthanum and neodymium based cuprates do not follow this scaling and appear to have depressed transition temperatures.
TL;DR: In this paper, photoelastic modulation and heterodyne detection were used to simultaneously measure the Faraday rotation and induced ellipticity in light transmitted by semiconducting and metallic samples.
Abstract: A sensitive polarization modulation technique uses photoelastic modulation and heterodyne detection to simultaneously measure the Faraday rotation and induced ellipticity in light transmitted by semiconducting and metallic samples. The frequencies measured are in the midinfrared and correspond to the spectral lines of a CO2 laser. The measured temperature range is continuous and extends from 35 to 330 K. Measured samples include GaAs and Si substrates, gold and copper films, and YBCO and BSCCO high temperature superconductors.
TL;DR: A method for an analysis of the angle-resolved photoemission data in two-dimensional anisotropic superconductors which directly yields the spectral function of the bosons mediating Cooper pairing is proposed.
Abstract: We propose a method for an analysis of the angle-resolved photoemission data in two-dimensional anisotropic superconductors which directly yields the spectral function of the bosons mediating Cooper pairing. The method includes a self-consistency check for the validity of the approximations made in the analysis. We explicitly describe the experimental data needed for implementing the proposed procedure.
TL;DR: In this article, it was shown that superconductivity is s-wave, not d-wave in the bulk of ruthenate compounds, such as doped Sr2YRuO6, GdSr2Cu2RuO8, and Gd2-zCezSr 2Cu 2RuO10 all superconduct in their SrO layers, which is why they have almost the same ~49 K onset temperatures for superconductivities.
Abstract: The widely held notion that high-temperature superconductivity originates in the cuprate-planes is proven to be faulty. In the cuprates such as YBa2Cu3O7, we argue that the superconductivity resides in the BaO layers. This superconductivity is s-wave, not d-wave, in the bulk. The trio of ruthenate compounds, doped Sr2YRuO6, GdSr2Cu2RuO8, and Gd2-zCezSr2Cu2RuO10 all superconduct in their SrO layers, which is why they have almost the same ~49 K onset temperatures for superconductivity.
TL;DR: Based on transport and magnetic measurements on Gd(Ba2−xPrx)Cu3O7+δ, and some other properties of high temperature superconductors (HTSC), Wang et al. as mentioned in this paper extracted similarities between 2D-EG and MOSFETs.
Abstract: Based on transport and magnetic measurements on Gd(Ba2−xPrx)Cu3O7+δ, and some other properties of high temperature superconductors (HTSC), we have extracted similarities between superconductors, two-dimensional electron gas (2D-EG) i.e. MOSFETs and ultrathin films of conventional superconductors. These are based on properties such as superconductor–insulator transition in superconductors and metal–insulator transition (MIT) in 2D-EG with doping and magnetic field, localization in transport conduction, quantum unit of resistance at MIT, larger change in resistance from critical doping to the insulating side in comparison with change from critical doping to the metallic side and strong electron–electron coupling. These similarities could lead to a deeper understanding of HTSC and 2D-EG systems.
TL;DR: The first large scale commercial application of high temperature superconducting (HTS) thin films has been in the area of passive microwave devices as discussed by the authors, which is particularly attractive for these applications because they have high transition temperatures and are relatively stable to atmospheric attack.
Abstract: The first large scale commercial application of high temperature superconducting (HTS) thin films has been in the area of passive microwave devices. Thallium based superconductors are particularly attractive for these applications because they have high transition temperatures (up to 127 K) and are relatively stable to atmospheric attack. Tl2Ba2CaCu2O8 films with high critical current density and low surface resistance can be fabricated by growing biaxially aligned films epitaxially on single crystal substrates. However, the processing of Tl based HTS thin films is particularly difficult due to the complexity of the crystal structure and the volatility and toxicity of thallium. Most Tl HTS films are fabricated using a two step process involving the deposition of an amorphous precursor followed by an ex situ thalliation anneal. The relative stability of the phases in the TBCCO system depends on the partial pressure of oxygen and thallous oxide, the processing temperature and the initial stoichiomet...
TL;DR: In this paper, the melting line of vortices and the anisotropy factor in high-pressure-grown Tl:1223 with a high Tc of 1335 K were determined experimentally.
Abstract: The fundamental and third-harmonic susceptibility response of YBa2Cu3O7−δ (YBCO) and TlBa2Ca2Cu3O10−y (Tl:1223) high-critical temperature (Tc) superconductors with preferentially oriented crystallites has been measured in various magnetic fields up to 14 T, and with very low ac field amplitude, to probe the melting transition of the vortex matter This method does not require large single crystals, being therefore suitable for high-Tc superconductors with small crystallites, prepared with high-pressure synthesis techniques We determine experimentally the melting line of vortices and the anisotropy factor in high-pressure-grown Tl:1223 with a high Tc of 1335 K Results from similar measurements on YBCO with preferentially oriented grains are consistent with both commonly accepted models of the melting line and values of the anisotropy factor, supporting the validity of our approach
TL;DR: In this paper, the performance of the superconductors fabricated by IBAD, and the fabrication costs, are to a great extent determined by the critical current densities of the grain boundaries.
Abstract: One of the most promising technologies for the fabrication of high-Tc cables is the ion-beam-assisted deposition (IBAD) technique. The performance of the superconductors fabricated by IBAD, and the fabrication costs, are to a great extent determined by the critical current densities of the superconductors’ grain boundaries. Since, in bicrystalline samples, overdoping has been found to improve the transport properties of grain boundaries in high-Tc superconductors, we have explored whether overdoping also enhances the critical currents of IBAD samples. The measurements show that, depending on the critical current density of the superconducting film, Jc (77 K) is increased by factors up to 2.2, also in applied magnetic fields of several tesla.
TL;DR: The model of van der Marel and Munzar as discussed by the authors, where the peak is the result of a transverse plasmon arising from a low frequency conductivity mode between the closely spaced planes, fits our data well.