Anisotropic pairing in superconductingSr2RuO4:Ru NMR and NQR studies

Abstract

Ru NMR and nuclear quadrupole resonance studies are reported on single-crystal ${\mathrm{Sr}}_2{\mathrm{RuO}}_4$ ${(T}_c=$0.7 K) with the same layered perovskite structure as ${\mathrm{La}}_2{\mathrm{CuO}}_4$. The Pauli spin susceptibility deduced from the Ru Knight shift is found to be largely enhanced by a factor of $\sim$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 $T_{1}T$=constant behavior well below $T_c,$ suggesting that the anisotropic pairing state is realized as in heavy-fermion and high-$T_c$ superconductors.