Journal of Superconductivity (J Supercond )

Publisher: Springer Verlag

Description

Journal of Superconductivity serves as the international forum for the most current information on the field. This highly acclaimed journal publishes peer-reviewed original papers and review articles that examine all aspects of the science and technology of superconductivity including new materials new mechanisms basic and technological properties new phenomena and small- and large-scale applications. Covering a wide scope of research the journal also features an annually updated bibliography on high T c superconductivity with entries cross-referenced by keywords developed by Dr. John Talvacchio of the Westinghouse R&D Center.

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  • Website
    Journal of Superconductivity website
  • Other titles
    Journal of superconductivity and novel magnetism, Superconductivity and novel magnetism
  • ISSN
    0896-1107
  • OCLC
    61187376
  • Material type
    Periodical, Internet resource
  • Document type
    Journal / Magazine / Newspaper, Internet Resource

Publisher details

Springer Verlag

  • Pre-print
    • Author can archive a pre-print version
  • Post-print
    • Author can archive a post-print version
  • Conditions
    • Authors own final version only can be archived
    • Publisher's version/PDF cannot be used
    • On author's website or institutional repository
    • On funders designated website/repository after 12 months at the funders request or as a result of legal obligation
    • Published source must be acknowledged
    • Must link to publisher version
    • Set phrase to accompany link to published version (The original publication is available at www.springerlink.com)
    • Articles in some journals can be made Open Access on payment of additional charge
  • Classification
    ​ green

Publications in this journal

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    ABSTRACT: A recombination radiation line of real excitons in dense two-dimensional electron gas at the [100] silicon surface is observed in luminescence spectra of metal-oxide-semiconductor (MOS) structures. A new effect of anisotropic paramagnetic reduction of the luminescence line indicates a strong influence of the Kondo correlations on electron paramagnetism of the excitons.
    Journal of Superconductivity 02/2008;
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    ABSTRACT: High-T c superconducting cuprates have two types of Fermi surfaces: simple-2D-tight-binding-band type (LSCO type) and the much deformed one (Bi2212 type). The difference is attributed to that of band parameter values, i.e., t′ ∼ −0.1 and t″ ∼ 0 versus t′ ∼ −0.3 and t″ ∼ 0.2 in terms of the second- and third-neighbor transfer energies t′ and t″, respectively (energy unit is the nearest-neighbor transfer energy t). Assuming a moderate value of on-site Coulomb energy U ∼ 6 and performing the variational Monte Carlo computation, we found that the two superconducting parameter domains exist in fact around these parameter sets, respectively, in which superconductivity predominates over spin density wave (SDW) due to the latter being at the brink of vanishing. Stripes were obtained in the first domain but tend to disappear in the second. In the latter domain there seems to exist parameter sets for which superconductivity appears without doping.
    Journal of Superconductivity 01/2006; 18:203-207.
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    ABSTRACT: Similarly to the half-doped manganese oxides with perovskite structure like La0.5Ca0.5MnO3, the double perovskite compound NaMn7O12 contains an equal number of Mn3+ and Mn4+ ions in the corner-sharing network of MnO6 octahedra and exhibits a CE order of the charge and spins of these ions at low temperature. Though, in NaMn7O12 the order is complete, the charge and spin ordering transitions are sharp and the system is free of disorder, phase coexistence or structural inhomogeneities thanks to the absence of chemical substitutions. Here we discuss two unusual features of the CE structure of NaMn7O12: (1) the e g 3d x 2−y 2 orbital ordering expected from the direct crystallographic observation of compressed Mn3+O6 octahedra below the charge ordering transition; (2) the existence of a large amount of low-energy excitations evidenced by the low temperature behavior of the specific heat. We propose a picture of nearly degenerate spin and orbital configurations of the CE structure arising from the peculiar orbital ordering. KEY WORDS:half-doped manganese oxides–CE-structure–orbital ordering–low-energy excitations.
    Journal of Superconductivity 01/2006; 18:75-80.
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    ABSTRACT: In the present work, the results of recent neutron scattering, STM, and NMR experiments concerning the structure of the vortex core in resistive state of the cuprates are discussed. It is demonstrated that “field-induced” antiferromagnetic (SDW) ordering observed in the SC state is the same as “temperature-induced” one arising above T c in the pseudogap (SDW) state. It is pointed out that in resistivity measurements, due to short mobile charge carrier relaxation time, a magnetic structure is sampled on much shorter time scale as compared with other techniques such as neutron scattering, Mossbauer effect, etc. It is noted that existing theoretical models mainly consider the SDW order only as competing to the SC one rather than stimulating the SC to appear at higher temperature. KEY WORDS:spin fluctuations–spin density wave–psseudogap–stripe structure
    Journal of Superconductivity 11/2005; 18(5):713-717.
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    ABSTRACT: We report experimental data showing the Feshbach shape resonance in the electron doped MgB2 where the chemical potential is tuned by Al, Sc, and C substitutions. The scaling of the critical temperature T c as a function of the Lifshitz parameter z = E Γ−E F, where E F is the chemical potential and E Γ is the energy of the Γ critical point where the σ Fermi surface changes from the 3D to a 2D topology, is reported. The resonant amplification of T c(z) driven by the interband pairing is assigned to a Feshbach shape resonance characterized by quantum superposition of pairs in states corresponding to different spatial location and different parity. It is centered at z = 0 where the chemical potential is tuned to a Van Hove-Lifshits feature for the change of Fermi surface dimensionality in the electronic energy spectrum in one of the subbands. In this heterostructure at atomic limit the multiband superconductivity is in the clean limit because the disparity and negligible overlap between electron wavefunctions in different subbands suppresses the single electron interband impurity scattering rate. The emerging scenario from these experimental data suggests that the Feshbach shape resonance could be the mechanism for high T c in particular nanostructured architectures. KEY WORDS:feshbach resonance–shape resonance–doped diborides
    Journal of Superconductivity 11/2005; 18(5):625-636.
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    ABSTRACT: We compare and contrast the polarizability of a d-wave superconductor in the pseudogap regime, within the precursor pairing scenario (dPG), and of a d-density-wave (dDW) state, characterized by a d-wave hidden order parameter, but no pairing. Our study is motivated by STM imaging experiments around an isolated impurity, which may in principle distinguish between precursor pairing and dDW order in the pseudogap regime of the high- $T_{c}$ superconductors. In both cases, the ${\bf q}$ -dependence of the polarizability is characterized by an azimuthal modulation, consistent with the d-wave symmetry of the underlying state. However, only the dDW result shows the fingerprints of nesting, with nesting wave vector ${{\bf Q}}=(\pi,\pi)$ , albeit imperfect, due to a nonzero value of the hopping ratio $t^\prime /t$ in the band dispersion relation. As a consequence of nesting, the presence of hole pockets is also reflected by the $({\bf q},\omega)$ dependence of the retarded polarizability.
    Journal of Superconductivity 11/2005; 18(5-6).
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    ABSTRACT: The variation of the critical temperature TcT_{c} and of the superconductive gaps as functions of doping (Al, C) in the diboride MgB2_{2} has been studied in the framework of the two-band Eliashberg theory and traditional phonon coupling mechanism. We have solved the two-band Eliashberg equations using first-principle calculations or simple assumptions for the variation of the relevant physical quantities. We have found that the experimental TcT_{c} curves can be exactly explained only if the Coulomb pseudopotential changes with x by tuning the Fermi level toward the σ band edge. We also found that a small amount of impurities changes the structural properties of the material, so we cannot treat the Mg1-xAl xB2_{1-x}{\rm Al} _{x}{\rm B}_{2} and MgB2-xCx_{2-x}{\rm C}_{x} systems as a contamination with Al or C of MgB2_{2}, but as new materials. Finally, we compare the predictions of our theory with the available experimental data. KEY WORDS:Magnesium diboride–Eliashberg equations–Electron-phonon interaction
    Journal of Superconductivity 11/2005; 18(5):791-795.
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    ABSTRACT: The phonon modes with strong electron–phonon interactions were investigated by two-phonon Raman scattering in p- and n-type high T c superconductors. In p-type superconductors, the strong electron–phonon interaction mode changes from the breathing mode at (π, π) to the half breathing mode at (π, 0) as carrier density increases across the optimum doping in LSCO or the 60K phase in YBCO. It is in good accordance with the change of the superconducting coherent peak position in k-space. In n-type superconductors, the strong electron–phonon interaction modes change from (0.4π, 0.4π) to (0.4π, 0) at the insulator–superconductor transition. Electron–phonon interactions play an important role in superconductivity. KEY WORDS:electron–phonon interaction–quasi-particle band
    Journal of Superconductivity 11/2005; 18(5):779-783.
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    ABSTRACT: Soft X-ray resonant diffraction is a new technique and there exist several examples of large resonant enhancements of charge and magnetic scattering that can be obtained at the L-edges of 3d transition metal oxides. Here we have employed resonant soft X-ray scattering at the manganese L edges which provide a direct measurement of the orbital ordering. We have studied the layered manganite La0.5Sr1.5MnO4 that displays charge, spin, and orbital ordering. Energy scans at constant wavevector show that there are two separate contributions to the observed scattering, direct Goodenough orbital ordering and strong cooperative Jahn–Teller distortions of the Mn3+ ions. Finally we will show how that the charge, spin and orbital degrees of freedom are strongly correlated in these materials. KEY WORDS:orbital ordering–manganites–X-ray scattering–synchrotron radiation
    Journal of Superconductivity 11/2005; 18(5):687-691.
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    ABSTRACT: Recent infrared absorption measurements performed at different pressures and temperatures on the La0.75Ca0.25MnO3 manganite provided an estimate of the insulator-to-metal transition temperature T IM(P), i.e., the P-T phase diagram of a pseudocubic manganite. Here we consider in detail the P- and T-dependence of the absorption spectral weights n *. The n *(T,P) behavior gives evidence of phase-separation between conducting and insulating domains in the P-T phase diagram, and allows to establish the occurrence of a characteristic temperature T * ≅ 0.6 T IM. For T > T *, when insulating domains decrease on decreasing temperature or on increasing pressure, it is possible to distinguish a metallic region (connected metallic domains) for T * < T < T IM, and an insulating region (disconnected metallic domains) for T > T IM. Below T *, no reduction of the insulating domains, that may still exist, occurs.
    Journal of Superconductivity 11/2005; 18(5-6).
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    ABSTRACT: A procedure has been developed to generate a persistent current in superconducting rings. The basis of the method is a magnetic circuit made of a permanent neodymium-iron-boron magnet and an iron core; the current induced in the superconductor comes only from the energy of the permanent magnet avoiding the power supply. This device would allow the generation of current densities ≥105 A/cm2. Furthermore, an inductive method to reduce the persistent current circulating on the samples is also shown, the utilization of a simple iron core being its base. This method avoids possible damages when the critical temperature is exceeded with a high persistent current circulating.
    Journal of Superconductivity 08/2005; 18(4).
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    ABSTRACT: We report a 11B NMR line shape and spin-lattice relaxation rate $(1/(T_1T))$ study of pure and lightly carbon-doped MgB $_{2-x}{\rm C}_x$ for $x = 0,0.02$ , and 0.04, in the vortex state and in magnetic field of 23.5 kOe. We show that while pure MgB $_2$ exhibits the magnetic field distribution from superposition of the normal and the Abrikosov state, slight replacement of boron with carbon unveils the magnetic field distribution of the pure Abrikosov state. This indicates a considerable increase of $H^c_{c2}$ with carbon doping with respect to pure MgB $_2$ . The spin-lattice relaxation rate $1/(T_1T)$ demonstrates clearly the presence of a coherence peak right below $T_{\rm c}$ in pure MgB $_2$ , followed by a typical BCS decrease on cooling. However, at temperatures lower than $\approx $ 10 K strong deviation from the BCS behavior is observed, probably from residual contribution of the vortex dynamics. In the carbon-doped systems both the coherence peak and the BCS temperature dependence of $1/(T_1T)$ weaken, an effect attributed to the gradual shrinking of the σ hole cylinders of the Fermi surface with electron doping.
    Journal of Superconductivity 08/2005; 18(4).
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    ABSTRACT: We have investigated effects of the lanthanide element Ln and the composition changes on the superconducting transition temperature T c in the Ru-1232 system, RuSr2(Gd1−x Lnx Ce1.8Sr0.2)Cu2Oz (Ln = Sm, Dy, and Ho). At first, in the case of the samples with Ln = Sm among almost the single 1232 phase samples, the values of the superconducting onset temperature T co are almost the same for x = 0.00–0.15, and each of the lattice parameters a and c is almost constant. While, in each of the cases of the samples with Ln = Dy and Ho, the sample with x = 0.05 shows the maximum values for both the superconducting onset temperature T co and the zero resistivity temperature T cz. Especially for the sample with Ln = Dy, the values of T co and T cz are 18.5 and 6.5 K, respectively. These are higher than those of the mother sample of RuSr2(GdCe1.8Sr0.2)Cu2Oz . Moreover, from variations of T co, lattice parameters of a and c in the RuSr2(Gd1−x Dyx Ce1.8Sr0.2)Cu2Oz system as a function of Dy content x, the relationship between the superconducting transition temperature and the lattice parameters in the present system are investigated.
    Journal of Superconductivity 08/2005; 18(4).
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    ABSTRACT: High temperature Superconductors (HTSCs) are a good candidate for developing THz radiation sensors. They are easy to manufacture and operate in the convenient temperature range of 80–140 K. The speed of operation of a THz sensor need to be controlled by a fast dissipation of heat, by the electrons which act as the sensing element. There is recently a surge in the development of fast and efficient low dimensional thermoelectric, temperature control devices. They would be ideal for cooling of the sensor, over the temperature interval of operation of the HTSCs. Status of these cooling devices towards achieving low temperature self cooling is discussed in the paper. Some results of the modeling study, carried out by the author, in an HTSC hot electron thermal sensor (HETS) are presented.
    Journal of Superconductivity 08/2005; 18(4).
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    ABSTRACT: Synthesis of the Bi-2212 compound in the Bi-Sr-Ce-Cu-O system has been already known. But, there has been no report on superconductivity of the compound yet. We have prepared many Bi-2212 samples partially substituted by Pb for Bi in the Bi-Sr-Ce-Cu-O system. The nominal composition is (Bi2−y Pby )Sr2(Sr1−x Cex )Cu2Oz . Then, we have investigated possibility of superconductivity for the samples. As a result, we find that a sample with nominal composition of x=0.23 and y=0.1, which is of almost the single 2212 phase, shows an anomaly at about 70 K in addition to temperature dependence of the resistivity like a semiconductor. Furthermore, the sample also shows a decrease of magnetic susceptibility starting at about 70 K with decreasing temperature. These experimental results can be considered to result from superconductivity of the 2212 phase in the Bi(Pb)-Sr-Ce-Cu-O system.
    Journal of Superconductivity 08/2005; 18(4).

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