TY - JOUR
T1 - Evidence of nodal superconductivity in Na 0.35CoO 2·1.3 H 2O
T2 - A specific-heat study
AU - Yang, H. D.
AU - Lin, J. Y.
AU - Sun, C. P.
AU - Rang, Y. C.
AU - Huang, C. L.
AU - Takada, K.
AU - Sasaki, T.
AU - Sakurai, H.
AU - Takayama-Muromachi, E.
PY - 2005/1
Y1 - 2005/1
N2 - 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.
AB - 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.
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U2 - 10.1103/PhysRevB.71.020504
DO - 10.1103/PhysRevB.71.020504
M3 - Article
AN - SCOPUS:16844364277
SN - 1098-0121
VL - 71
JO - Physical Review B - Condensed Matter and Materials Physics
JF - Physical Review B - Condensed Matter and Materials Physics
IS - 2
M1 - 020504
ER -