Evidence of nodal superconductivity in Na 0.35CoO 2·1.3 H 2O: A specific-heat study

H. D. Yang, J. Y. Lin, C. P. Sun, Y. C. Rang, C. L. Huang, K. Takada, T. Sasaki, H. Sakurai, E. Takayama-Muromachi

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Abstract

Comprehensive low-temperature specific-heat data C(T,H) of Na 0.35CoO 2 · 1.3 H 2O with temperature T down to 0.6 K and the magnetic field H up to 8 T are presented. In the normal state, the values of γ n = 13.94 mJ/mol K 2 and Debye temperature Θ D = 362 K are reported. At zero field, a very sharp superconducting anomaly was observed at T c=4.5 K with ΔC/γ nsT c=1.45 if the specific-heat jump is normalized to the superconducting volume fraction, which is estimated to be 47.4% based on the consideration of entropy balance at T c for the second-order superconducting phase transition. In the superconducting state, the electronic contribution C es at H=0 can be well described by the model of the line nodal order parameter. In low H, δγ(H) ∝ H 1/2, which is also a manifestation of the line nodes. The behaviors of both T C(H) and γ(H) suggest the anisotropy of H c2, or possible crossovers or transitions occurring in the mixed state.

Original languageEnglish
Article number020504
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume71
Issue number2
DOIs
Publication statusPublished - 2005 Jan

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics

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