Unconventional Superconductivity and Electron Correlations in the Cobalt Oxyhydrate Na0.35CoO2·yH2O from Nuclear Quadrupole Resonance
Tatsuya Fujimoto, Guo-qing Zheng, Y. Kitaoka, R. L. Meng, J. Cmaidalka, C. W. Chu
DOI 10.1103/PhysRevLett.92.047004 · Physical Review Letters
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Abstract
We report a careful Co59 nuclear quadrupolar resonance measurement on the recently discovered cobalt oxyhydrate Na0.35CoO2·yH2O superconductor from T=40 K down to 0.2 K. We find that in the normal state the spin-lattice relaxation rate 1/T1 follows a Curie-Weiss type temperature (T) variation, 1/T1T=C/(T−θ), with θ=−42 K, suggesting two-dimensional antiferromagnetic spin correlations. Below Tc=3.9 K, 1/T1 decreases with no coherence peak and follows a Tn dependence with n≃2.2 down to ∼2.0 K but crosses over to a 1/T1∝T variation below T=1.4 K, which suggests non-s-wave superconductivity. The data in the superconducting state are most consistent with the existence of line nodes in the gap function.
Source-reported materials — not catalogue approval
| Formula | Reported Tc (K) | Pressure (GPa) | Type |
|---|---|---|---|
| Na0.35CoO2·yH2O Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 3.9 | Pressure not reported | onset |
| Na0.35CoO2·yH2O Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 3.8 | Pressure not reported | unknown |
| CeIrIn5 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 0.6 | Pressure not reported | onset |
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