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@TECHREPORT{Klein:872968,
      author       = {Klein, N.},
      title        = {{E}lectrodynamic properties of oxide superconductors},
      volume       = {3773},
      number       = {Juel-3773},
      address      = {Jülich},
      publisher    = {Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag},
      reportid     = {FZJ-2020-00425, Juel-3773},
      series       = {Berichte des Forschungszentrums Jülich},
      pages        = {101 p.},
      year         = {2000},
      abstract     = {The electrodynamic properties of oxide high temperature
                      superconductors are reviewed. Most of the experimental data
                      are from thin films and bulk single crystals of
                      YBa$_{2}$Cu$_{3}$O$_{7-x}$, which - together with thin films
                      of thallium-based oxide uperconductors provide the lowest
                      microwave losses making epitaxially grown thin films
                      attractive for applications in microwave technology. Among
                      the various techniques for the determination of the
                      electrodynamic response of superconducting thin filmscavity,
                      dielectric, and planar resonators are the most successful
                      ones for the frequencyrange from 1 to 100 GHz. For the
                      millimeter and submillimeter wave range nonresonant
                      transmission techniques in frequency and time domain have
                      been used successfully. Bulk single crystals have been
                      studied by various types of cavity perturbationtechniques.
                      YBa$_{2}$Cu$_{3}$O$_{7-x}$ bulk single crystals and
                      epitaxial thin films exhibit a steep drop ofthe surface
                      resistance R$_{s}$ just below the transition temperature
                      T$_{c}$, to values at 77 K which are about 300 $\mu \Omega$
                      at 10 GHz. The observed dependence on the frequency fcan be
                      described by f$^{A}$ with sample-dependent A values between
                      1.5 and 2. At lower temperatures R$_{s}$ (T) is
                      substantially different both from that predicted by BCS
                      theoryand observed experimentally for conventional
                      superconductors. Typically, R$_{s}$ (T) exhibits a plateau
                      between 30 and 70 K corresponding to a frequency-dependent
                      maxirnurnin the real part of the conductivity. The observed
                      correlation of the height of this maximum to the defect
                      density indicates that above about 30 K the
                      electrodynamicresponse is dominated by a strong decrease of
                      the quasiparticle lifetime just below T$_{c}$. Below
                      T$_{c}$/2 the situation is still quite unclear. The observed
                      temperaturedependences both for R$_{s}$ and the London
                      penetration depth $\lambda_{L}$ range from weak exponential
                      corresponding to energy gaps more than two times smaller
                      than expectedfrom weak-coupling BCS theory over quadratic to
                      linear dependences. In any case, a high residual surface
                      resistance R$_{res}$ = R$_{s}$(T $\rightarrow$ 0) remains.
                      In particular, the lowtemperature regime was found to be
                      strongly affected by the amount and ordering of oxygen
                      vacancies in the copper-oxygen chains. The active rote of
                      the copper-oxygenchains as a conducting subsystem was worked
                      out theoretically within a strongcoupling theory based on
                      phonon-mediated superconductivity and can
                      quantitativelyexplain some of the observed results. In
                      particular, gapless superconductivity can be easily achieved
                      from magnetic pair breaking in the copper-oxygen chains.
                      $\textit{d}$-wave superconductivity, as expected for
                      superconductivity mediated by spin fluauationsinstead of
                      phonons, leads to a gapless behavior as well. The observed
                      temperature dependences of $\lambda_{L}$ and R$_{s}$ can be
                      explained to some extent within $\textit{d}$-wave models.In
                      contradiction to the hole doped cuprates (as e.g.
                      YBa$_{2}$Cu$_{3}$O$_{7-x}$), the electron doped cuprates
                      exhibit an electromagnetic response which is similar to
                      predictionsfor an isotropic s-wave order parameter.},
      cin          = {PRE-2000 ; Retrocat},
      cid          = {I:(DE-Juel1)PRE2000-20140101},
      pnm          = {899 - ohne Topic (POF3-899)},
      pid          = {G:(DE-HGF)POF3-899},
      typ          = {PUB:(DE-HGF)3 / PUB:(DE-HGF)29},
      url          = {https://juser.fz-juelich.de/record/872968},
}