Journal article

Superconducting energy gap and c-axis plasma frequency of (Nd,Sm)FeAsO0.82F0.18 superconductors from infrared ellipsometry

  • Dubroka, Adam Department of Physics and Fribourg Center for Nanomaterials, University of Fribourg, Switzerland
  • Kim, Kyung Wan Department of Physics and Fribourg Center for Nanomaterials, University of Fribourg, Switzerland
  • Rössle, Matthias Department of Physics and Fribourg Center for Nanomaterials, University of Fribourg, Switzerland
  • Malik, Vivek Kumar Department of Physics and Fribourg Center for Nanomaterials, University of Fribourg, Switzerland
  • Drew, Alan J. Department of Physics and Fribourg Center for Nanomaterials, University of Fribourg, Switzerland
  • Liu, R. H. Hefei National Laboratory for Physical Sciences at Microscale and Department of Physics, University of Science and Technology of China, Hefei, Anhui, China
  • Wu, G. Hefei National Laboratory for Physical Sciences at Microscale and Department of Physics, University of Science and Technology of China, Hefei, Anhui, China
  • Chen, X. H. Hefei National Laboratory for Physical Sciences at Microscale and Department of Physics, University of Science and Technology of China, Hefei, Anhui, China
  • Bernhard, Christian Department of Physics and Fribourg Center for Nanomaterials, University of Fribourg, Switzerland
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    29.08.2008
Published in:
  • Physical Review Letters. - 2008, vol. 101, no. 9, p. 097011
English We present far-infrared ellipsometric measurements of polycrystalline samples of the pnictide superconductor RFeAsO0.82F0.18 (R=Nd and Sm). We find evidence that the electronic properties are strongly anisotropic such that the optical spectra are dominated by the weakly conducting c-axis response similar to the cuprate high-temperature superconductors. We deduce an upper limit of the c-axis superconducting plasma frequency of Ω pl,cSC ≤ 260 cm⁻¹ corresponding to a lower limit of the c-axis magnetic penetration depth of Λc≥ 6 µm and Λ c/ Λ ab≥ 30 as compared to Λ ab=185 nm from muon spin rotation [A. Drew et al., arXiv:0805.1042 [Phys. Rev. Lett. (to be published)]]. We also observe a gaplike suppression of the conductivity in the superconducting state with a shoulderlike feature at Ω SC* ≈300 cm⁻¹ and spectral shape which is consistent with an unconventional order parameter with 2 Δ≈Ω SC* ≈ 37 meV.
Faculty
Faculté des sciences
Department
Physique
Language
  • English
Classification
Physics
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https://folia.unifr.ch/unifr/documents/300927
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