We report the spin susceptibility in the superconducting state of the cobalt oxide superconductor Nax CoO2 · 1.3 H2 O, via the 59Co Knight shift measurements. Along both a- and c-axis directions, the shift decreases below Tc. At T = 1.7 K, the shift along the a-axis, Ka, increases with increasing the strength of magnetic field (H), following a sqrt(H) variation. Together with the T3 dependence of the spin-lattice relaxation rate, 1 / T1, these results indicate unambiguously that the Cooper pairs are in the spin-singlet form and that there exist nodes in the gap function. The data are most consistent with a d-wave symmetry.
- Na CoO · y H O
- d-Wave symmetry
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics
- Electrical and Electronic Engineering