Quantum critical behavior in superconducting Nax(H3O)zCoO2∙yH2O observed in a high-field Co NMR experiment
Y. Ihara, H. Takeya, K. Ishida, C. Michioka, K. Yoshimura, K. Takada, T. Sasaki, H. Sakurai, E. Takayama-Muromachi
DOI 10.1103/PhysRevB.75.212506 · Physical Review B
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Abstract
Co nuclear magnetic resonance (NMR) measurements are performed on superconducting Nax(H3O)zCoO2∙yH2O with a bilayered hydrate structure. External fields are applied exactly parallel to the CoO2 plane on a high-quality powdered sample, which is aligned in a strong magnetic field. When superconductivity is suppressed by external magnetic fields, the nuclear spin-lattice relaxation rate divided by temperature (1∕T1T) continues to increase down to Tc(H), which is the superconducting transition temperature under a magnetic field H. From the analyses of the temperature variation, it was found that a sample with Tc∼4.8K, which is the maximum Tc, possesses magnetic fluctuations with a quantum critical character. This suggests the intimate relationship between superconductivity and quantum critical fluctuations in the hydrate cobaltate. We determined Tc(H) and constructed the Hc2−Tc phase diagram from the present NMR measurements. The field dependence of Tc(H) is discussed.
Source-reported materials — not catalogue approval
| Formula | Reported Tc (K) | Pressure (GPa) | Type |
|---|---|---|---|
| Nax(H3O)zCoO2∙yH2O Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 4.8 | Pressure not reported | onset |
| Nax(H3O)zCoO2∙yH2O Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 4.8 | Pressure not reported | onset |
| Nax(H3O)zCoO2∙yH2O Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 4.8 | Pressure not reported | onset |
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