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  • 1
    Electronic Resource
    Electronic Resource
    Anomalous temperature dependence of the magnetic field penetration depth in superconducting UBe13 (1986)
    Springer
    The European physical journal 64 (1986), S. 175-188 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We report the first measurements of the magnetic-field penetration depth λ in the heavy electron superconductor UBe13, performed using a SQUID magnetometer. We find the temperature dependence of λ(T)-λ(0) to follow aT 2 law at low temperatures, giving further evidence of extreme gap anisotropy in this compound. We calculate the temperature dependence expected for a variety of anisotropic states, including those representing certain classes of “exotic” pairing. In general situations, the supercurrent is not parallel to the vector potential, and a more complicated field penetration takes the place of the normal Meissner effect. We argue that the data are consistent with an energy gap with point nodes on the Fermi surface but inconsistent with the large value of the Landau parameterF 1 S expected for a translationally invariant Fermi liquid with large effective mass.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01303700
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    London field penetration in heavy fermion superconductors (1991)
    Springer
    The European physical journal 82 (1991), S. 243-255 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We present results of a series of high resolution, low fielddc-magnetization measurements on the heavy fermion superconductors UPt3, UBe13, U1−x Th X Be13 and CeCu2Si2, from which values of the magnetic penetration depth λ can be extracted. A study of the temperature variation reveals aT 2 power law in all cases. This can not be reconciled with a BCS-like isotropic energy gap but may be explained by the presence of low energy quasiparticle states inside the gap. In the case of very pure superconductors, one such possibility is the assumption of point-nodes in the gap function. We argue, however, that an interpretation in terms of resonant impurity scattering in various anisotropic superconducting states is more likely to explain a broad range of experimental data. The results on differently oriented single crystals of UBe13 and UPt3 reveal no pronounced anisotropy related to the crystal lattice. Absolute values of λ atT=0 are deduced by a novel method in which the field is first screened out from the sample by means of an evaporated superconducting film (of lowerT c ). Above this lowerT c the sudden penetration of field into the sample can then be measured absolutely.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01324334
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Thermal conductivity of Zn, Pr and Tb doped YBCO single crystals: Theory and experiment (1995)
    Springer
    Journal of superconductivity 8 (1995), S. 453-456 
    Details
    ISSN: 1572-9605
    Keywords: Doping ; Thermal Conductivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The thermal conductivity K(T) vs temperature has been measured for (Y,Pr)Ba2Cu3O7, (Y,Tb)Ba2Cu3O7 and YBa2(Cu,Zn)3O7 single crystals from 10≤T≤280K. For YBa2Cu3O7(YBCO), a strong enhancement in K(T) is observed for T≤Tcwith a peak in K(T) at approximately T≈Tc/2 with a sharp change in slope of K(T) at Tc. These results are similar to those reported previously. For the selectively doped YBCO, the peak in K(T) is shifted to lower temperatures and occurs at T≈ 20K independent of Tc and the impurity concentration. In addition, the sharp change in slope of K(T) at Tc is not apparent for the doped crystals. These results are discussed along with a theoretical model for electronic conduction including both impurity and inelastic scattering from spin fluctuations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00722828
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  • 4
    Electronic Resource
    Electronic Resource
    Effects of Fermi Surface Anisotropy on Unconventional Superconductivity in UPt3 (1998)
    Springer
    Journal of low temperature physics 111 (1998), S. 73-98 
    Details
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We discuss the weak-coupling BCS theory of the heavy fermion superconductor UPt 3 , accounting for that system's anisotropic, multisheeted Fermi surface by expanding the order parameter and pair potential in terms of appropriate basis functions of the irreducible representations of the D 6h crystal point group. Within a phenomenological model for the electronic structure of UPt 3 chosen to capture the qualitative features of local density functional calculations and de Haas–van Alphen measurements, we show how Fermi surface anisotropy can favor pairing in certain symmetry classes, and influence the phase diagram of unconventional superconductors. We also calculate the Ginzburg–Landau coefficients, focussing on those coefficients relevant to current theories of the UPt 3 phase diagram.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022298208486
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  • 5
    Electronic Resource
    Electronic Resource
    Electromagnetic skin depth of unconventional superconductors (1992)
    Springer
    Journal of low temperature physics 88 (1992), S. 395-420 
    Details
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: We discuss aspects of the response to an externally applied electromagnetic field of a superconductor with an order parameter of E lg symmetry, possibly realized in the heavy fermion compound UPt 3 . From the electromagnetic response function K(% MathType!MTEF!2!1!+- % feaafeart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn % hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr % 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqaqpepeea0xe9qqVa0l % b9peea0lb9sq-JfrVkFHe9peea0dXdarVe0Fb9pgea0xa9pue9Fve9 % Ffc8meGabaqaciGacaGaaeqabaWaaeaaeaaakeaaceqGXbGba4aaaa % a!3885! \[ {\rm{\mathord{\buildrel{\lower3pt\hbox{$\scriptscriptstyle\rightharpoonup$}} \over q} }} \], Ω) we extract the low-frequency reactive response, which determines the inductive skin depth, including the effects of impurity potential scattering with arbitrary phase shifts. Comparison with a series of recent experiments on UPt 3 at temperatures T ≪ T csuggests that a state with E lg symmetry may be a good candidate for the ground state of this material. While comparison to some experiments are promising at low temperature, we are unable to fit the experimental data over the entire temperature range with a single normal-state elastic scattering parameter Τ, and discuss possible explanations for this discrepancy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00126602
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  • 6
    Electronic Resource
    Electronic Resource
    Low-temperature properties of anisotropic superconductors with kondo impurities (1994)
    Springer
    Journal of low temperature physics 96 (1994), S. 185-206 
    Details
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We present a self-consistent theory of superconductors in the presence of Kondo impurities, using large-N slave-boson methods to treat the impurity dynamics. The technique is tested on the s-wave case and shown to give good results compared to other methods forT K 〉T c . We calculate low temperature thermodynamic and transport properties for various superconducting states, including isotropic s-wave and representative anisotropic model states with line and point nodes on the Fermi surface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00752405
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