GLORIA

GEOMAR Library Ocean Research Information Access

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    Effects of spin-orbit interaction and crystal fields on superconductingp-wave pair states and their collective excitations in cubic systems (1986)
    Springer
    Journal of low temperature physics 65 (1986), S. 13-46 
    Details
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Superconducting pair states for systems with strong spin-orbit interaction and crystallographic anisotropy are usually assumed to transform as the basis functions of the irreducible representations Γ n of the appropriate point group. Transitions to pair states belonging to different irreducible representations are supposed to occur at different transition temperaturesT c (Γ n ). Here it is shown forp-wave states that, as soon as nonlinear terms in the gap equation or quartic terms in the Ginzburg-Landau free energy are taken into account, linear combinations of pair states belonging to different irreducible representations can result. This applies to all those states that are not solutions of the gap equation when the pairing interaction is of the isotropic form V0 $$\hat k \cdot \hat k'$$ used in the theory of superfluid3He. The spectrum of collective excitations of those states, which are actually solutions of the gap equation, becomes much more complex when spin-orbit interaction and crystal field effects are taken into account by assuming different transition temperaturesT c (Γ n ). In particular, a number of additional modes are found whose frequencies scale as ω2 ∝ ln[T c (Γ n )/T c (Γ m )]. If the deviation from the isotropic interaction is not very large, these modes will have very low frequencies. They couple to density fluctuations toO(q2) due to particle-hole asymmetry. This can be a large effect in heavy fermion compounds because of the sharp peak in the density of states. These modes could, therefore, be very well responsible for the peaks in the acoustic attenuation observed just belowT c .
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00685400
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Quasiclassical theory of the upper critical field of high-field superconductors. Application to momentum-dependent scattering (1991)
    Springer
    Journal of low temperature physics 84 (1991), S. 381-464 
    Details
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A theory of the upper critical field is developed which is sufficiently general to incorporate strong coupling effects, anisotropy of both Fermi surface and pairing interaction, and momentum dependent scattering, including exchange and spin-orbit scattering. It is not necessary to assume that spin-orbit scattering is a small fraction of the total scattering. An important improvement in this theory is the correct treatment of the spatial dependence of the anomalous Green function and the order parameter in the mixed state. In the presence of anisotropy this is, in general, not described with sufficient accuracy by the Abrikosov vortex lattice. Application of this theory to anisotropy effects, with the clean limit taken in most cases, have been published elsewhere and additional studies will appear in the near future. In this paper we concentrate on the effects arising from the momentum dependence of the elastic scattering. If spin-orbit scattering forms a sizeable fraction of the total scattering it is necessary to take its explicit momentum dependence into account. When this is done we find that spin-orbit scattering is actually less effective in reducing paramagnetic limiting.p- andd-wave scattering have a marked effect on the upper critical fieldH c2 at low reduced temperatures, partially cancelling each other.d-wave scattering raisesH c2(O), but for physically acceptable parameter value is not sufficient to explain the apparent absence of paramagnetic limiting in some high-field superconductors. For a complete description of the upper critical field, other effects mentioned above need to be taken into account, but for superconductors of intermediate purity the momentum dependence of the scattering cannot be ignored. The greatest problem remaining in our quest for a complete understanding of the upper critical field appears to be an accurate determination of the relevant normal state properties.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00683526
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Local and Nonlocal Effects on the Surface Resistance of d-Wave Superconductors (1999)
    Springer
    Journal of low temperature physics 117 (1999), S. 1295-1299 
    Details
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Evidence for d-wave superconductivity from measurements of the local conductivity is rather indirect and not very compelling. Very recently, experimental data on the surface resistance taken at five different frequencies on very high quality single crystals of YBa 2 Cu 3 O 7 have become available. Having the frequency as additional variable provides a much more stringent test for the predictive powers of the d-wave model. Because of the high quality of the samples we expect that at low temperatures the nonlocal limit applies to the surface resistance. A nonlocal relation between current and field would allow a direct investigation of the order parameter anisotropy by varying the wave vector q of the radiation relative to the crystal axes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022504608433
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Surface impedance of epitaxial YBCO thin films — Comparison of experimental data with a d-wave theory of superconductivity (1996)
    Springer
    Journal of low temperature physics 105 (1996), S. 503-508 
    Details
    ISSN: 1573-7357
    Keywords: 05.70 Ln ; 05.70 Jk ; 64
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The surface impedance of two 350nm thick YBCO films was measured for temperatures between 4.2K and 150K in a copper cavity at 87 GHz. Both films, one grown by electron beam evaporation on MgO, the other one by high oxygen-pressure dc sputtering from a stoichiometric target on LaAlO3, provide critical temperatures of about 91K, low residual surface resistances of Rs(4.2K) 〈 1mΩ and low specific resistivities in the normal state of ϱ(100K) 〈 85μΩcm. The experimental data obtained on these two films are compared to a d-wave model of superconductivity which incorporates elastic and inelastic scattering. Good agreement between theory and the experimental results for both the surface resistance and the penetration depth in the whole temperature range is achieved for scattering phase shifts near 0.4π and order parameter amplitudes in the range of 2Δ0(0)/kBTc = 6.0 – 7.5 without subtracting an extrinsic residual surface resistance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00768435
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Electromagnetic response of unconventional superconductors (1988)
    Springer
    The European physical journal 72 (1988), S. 139-159 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The magnetic field penetration depth, surface resistance and far infrared reflectivity are calculated for two anisotropic order parameters having either points or lines of nodes in the energy gap. Resonant impurity scattering is taken into account for a wide range of scattering rates. Comparison with experimental results on heavy Fermion superconductors shows that the order parameter cannot be deduced unambiguously from the temperature dependence of the penetration depth. Fits to surface resistance measurements on UBe13 are best in the Born approximation, rather than the unitarity limit. Experiments on high-T c materials are largely inconclusive, offering little support for the applicability of BCS theory and providing no evidence against novel pairing interactions leading to unusual order parameters.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01312129
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Nonlocal Effects on the Surface Resistance of High-Temperature Superconductors with (100) and (110) Surfaces (1999)
    Springer
    Journal of superconductivity 12 (1999), S. 385-393 
    Details
    ISSN: 1572-9605
    Keywords: High-temperature superconductors ; theory ; nonlocal effects ; surface resistance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The low-temperature surface resistance R s of d-wave superconductors is calculated as function of frequency assuming normal state quasiparticle mean free paths l in excess of the penetration depth. Results depend strongly on the geometric configuration. In the clean limit, two contributions to R s with different temperature dependencies are identified: photon absorption by quasiparticles and pair breaking. The size of nonlocal corrections, which can be positive or negative depending on frequency decreases for given l as the scattering phase shift δ N is increased. However, except in the unitarity limit δ N =0.5π, nonlocal effects should be observable.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007709501131
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Microwave surface resistance of granular anisotropic superconductors (1990)
    Springer
    Journal of superconductivity 3 (1990), S. 269-276 
    Details
    ISSN: 1572-9605
    Keywords: Surface resistance ; electrophoretic films ; Y1Ba2Cu3O7−δ grain aligned
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The effective-medium approach is used to calculate the surface resistance of materials consisting of uniaxial grains imbedded in an isotropic background. The grains are taken to be superconducting in theab-plane. The mean free path dependence of theac-conductivity in the superconducting state is explicitly taken into account. In thec-direction the grains are assumed to have negligible conductivity. The background is taken to be a normal Drude conductor. This model should represent a reasonable description of high-T c materials. Large residual surface resistances can be fitted if the samples contain 10–20% background material, which is a good conductor. Agreement between theory and experiment can be improved if gap anisotropy is taken into account.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00625267
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...