Anisotropic pairing in superconducting Sr2RuO4: Ru NMR and NQR studies

NMR and nuclear quadrupole resonance studies are reported on single-crystal Sr2RuO4 (T-c=0.7 K) with the same layered perovskite structure as La2CuO4. The Pauli spin susceptibility deduced from the Ru Knight shift is found to be largely enhanced by a factor of similar to 5.4 as compared with the value from the band calculation. In the superconducting state, the nuclear spin-lattice relaxation rate 1/T-1 exhibits a sharp decrease with no coherence peak just below T-c and the T1T=constant behavior well below T-c, suggesting that the anisotropic pairing state is realized as in heavy-fermion and high-T-c superconductors.