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

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    • Author can archive a pre-print version
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    • Author can archive a post-print version
  • Conditions
    • Author's pre-print on pre-print servers such as arXiv.org
    • Author's post-print on author's personal website immediately
    • Author's post-print on any open access repository after 12 months after publication
    • Publisher's version/PDF cannot be used
    • Published source must be acknowledged
    • Must link to publisher version
    • Set phrase to accompany link to published version (see policy)
    • Articles in some journals can be made Open Access on payment of additional charge
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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: The symmetry of the Bloch functions in the conduction band of tetragonal and orthorhombic La2CuO4 is examined for the existence of symmetry-adapted and optimally localizable (usual or spin-dependent) Wannier functions. It turns out that such Wannier functions do not exist in the tetragonal phase. In the orthorhombic phase, on the other hand, the Bloch functions can be unitarily transformed in three different ways into optimally localizable Wannier functions: they can be chosen to be adapted to each of the three phases observed in the pure or doped material, that is, to the antiferromagnetic phase, to the superconducting phase or to the phase evincing neither magnetism nor superconductivity. This group-theoretical result is proposed to be interpreted within a nonadiabatic extension of the Heisenberg model. Within this model, atomic-like states represented by these Wannier functions are responsible for the stability of each of the three phases. However, all the three atomic-like states cannot exist in the tetragonal phase, but are stabilized by the orthorhombic distortion of the crystal. A simple model is proposed which may explain the physical properties of La2-x Sr x CuO4 as a function of the Sr concentration x.
    Journal of Superconductivity 08/2006; 18(4):1-22.
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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 have studied the variation of superconducting critical temperature T c as a function of electron doping in the Mg10B2 system using Sc for Mg substitution. The critical temperature in the10B isotope substituted system Mg1− x Sc x 10B2 increases by increasing the scandium content x in the range 0xT c of the natural boron system Mg1− x Sc x B2 is nearly constant. The overall difference of T c in Mg1− x Sc x B2 as function of x between the natural B and 10B isotope system seems to indicate that the isotope effect shows large variations with electron doping as expected for the T c enhancement driven by a shape resonance.
    Journal of Superconductivity 11/2005; 18(5):67-70.
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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: 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: A large positive magnetoresistance (up to tens of percents) is observed in both underdoped (x superconducting La2− xSrxCuO4 (LSCO) epitaxial thin films, at temperatures far above the superconducting critical temperature T c . In the underdoped regime, this magnetoresistance cannot be described by the Kohler rule and is due to the influence of superconducting fluctuations. On the other hand, in the overdoped regime, the Kohler rule does not seem to be violated. The strong magnetoresistance above T c can be related to the preformed superconducting pairs existing well above T c but forming a phase coherent superconducting state below T c . The observations support the idea of a close relation between the pseudogap and the superconducting gap and provide evidence for the presence of pre-pairs above T c . Both the observed fluctuations and the observed magnetoresistance are in accordance with the existence of 1D-like stripes. These results are further supported by recent high magnetic field measurements (up to 55 T) of the transverse magnetoconductivity σ xy, which goes to zero for T→0 K.
    Journal of Superconductivity 11/2005; 18(5):197-201.
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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).