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  • 1985-1989  (5)
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Material
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Year
  • 1
    Electronic Resource
    Electronic Resource
    Strong-coupling effects in high-T c superconductors (1987)
    Springer
    The European physical journal 67 (1987), S. 147-154 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract It is conceivable that the high-T c superconducting perovskites are conventional electronphonon superconductors. In this case one expects significant strong-coupling effects because of the unusually high ratiok B T c /ħ〈ω〉 of the order 0.1 and greater. We use a set of reasonable models for the Eliashberg function α2 F(ω) (which takes into account available information on the phonon spectra and which fit the measuredT c 's) and calculate strong-coupling effects in the specific heatc s (T)/γT c , the ratio Δ0/k B T c , the critical fieldsH c (T) andH c2 (T) including Pauli limiting, and other measurable quantities. Strongcoupling corrections turn out to be in the range of 0 to about 100%, depending on the quantity of interest. We discuss the perspectives of using strong-coupling effects as indicators for conventional electron-phonon superconductivity in the new materials.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01303974
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Thermodynamic behaviour of type II superconductors at low induction for arbitrary temperature and impurity content (1987)
    Springer
    The European physical journal 68 (1987), S. 49-56 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Using Eilenberger's equations in vortex symmetry, we calculate numerically the structure of an isolated flux line and the lower critical field of a type II superconductor as functions of temperature and impurity content. In order to describe in addition the low-induction regime of the mixed state, a circular-cell approximation is introduced and compared with recent exact results of the Eilenberger theory. The agreement is excellent, if the flux-line overlap is weak. Within this approach it is shown that the nature of the phase transition at the lower critical field depends very sensitively on anisotropies of the Fermi surface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01307863
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Theory of the generalized Ginzburg-Landau parameter κ2 for strong-coupling superconductors at arbitrary impurity concentration (1989)
    Springer
    Journal of low temperature physics 77 (1989), S. 235-256 
    Details
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We study strong-coupling effects on the slope of the magnetization curve at the upper critical field of a type II superconductor, parametrized by the generalized Ginzburg-Landau parameter κ2. The use of the quasiclassical approach to the BCS-Gorkov theory, valid for all temperatures, allows us to present the calculations in a transparent manner. We obtain closed expressions for κ2 in terms of the solution of the eigenvalue problem determining the upper critical field, which we evaluate numerically. In the weak-coupling limit, previous results are reproduced, apart from a small correction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00681534
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    A simple interpolation method for the free energy of a type II superconductor in the mixed state (1987)
    Springer
    Journal of low temperature physics 66 (1987), S. 55-67 
    Details
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A simple interpolation method is proposed for the construction of a surprisingly accurate free energy of a type II superconductor, which uses only properties at the upper and lower critical fields. The validity of the approach is checked against exact numerical results. The interpolation formula yields very good magnetization curves. For low-κ, type II superconductors small systematic deviations are obtained, which tend to reduce the type II/1 region (vortex attraction). A proper discussion of these delicate effects requires a very precise knowledge of the free energy for all inductions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00681467
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Lower critical field and magnetization of strong-coupling, type II superconductors in the dirty limit (1988)
    Springer
    Journal of low temperature physics 71 (1988), S. 323-340 
    Details
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Usadel's dirty-limit version of the Gorkov-Eilenberger theory including strong-coupling effects is used to calculate the lower critical field of superconducting alloys. The results of the (rigorous) numerical study, which is valid for all temperatures and Ginzburg-Landau parameters κ, are compared with experiments and with the existing weak-coupling theory. One achieves agreement with the bulk of the experimental results only if κ is properly adjusted. In addition, it is shown that a circular-cell approximation for the vortex state yields highly accurate magnetization curves, which are influenced in a characteristic way by strong electron-phonon coupling.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00116866
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    Paper (German National Licenses)
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