Unconventional Superconductivity and Electron Correlations in the Cobalt Oxyhydrate [Formula presented] from Nuclear Quadrupole Resonance

We report a careful [Formula presented] nuclear quadrupolar resonance measurement on the recently discovered cobalt oxyhydrate [Formula presented] superconductor from [Formula presented] down to 0.2 K. We find that in the normal state the spin-lattice relaxation rate [Formula presented] follows a Curie-Weiss type temperature ([Formula presented]) variation, [Formula presented], with [Formula presented], suggesting two-dimensional antiferromagnetic spin correlations. Below [Formula presented], [Formula presented] decreases with no coherence peak and follows a [Formula presented] dependence with [Formula presented] down to [Formula presented] but crosses over to a [Formula presented] variation below [Formula presented], which suggests non-[Formula presented]-wave superconductivity. The data in the superconducting state are most consistent with the existence of line nodes in the gap function.