59Co-NMR Knight Shift of Aligned Crystals and Polycrystalline Samples of Superconducting Na0.3CoO2.1.3H2O

TL;DR

This study investigates the temperature dependence of 59Co-NMR Knight shifts in Na0.3CoO2.1.3H2O, revealing singlet pairing in the superconducting state and consistent upper critical field measurements with resistivity data.

Contribution

It provides detailed NMR Knight shift measurements on aligned and polycrystalline samples, confirming singlet pairing and aligning NMR results with resistivity data for this superconductor.

Findings

Knight shift decreases below Tc, indicating singlet pairing

Upper critical fields from NMR are consistent with resistivity measurements

Results support the understanding of superconducting pairing symmetry in Na0.3CoO2.1.3H2O

Abstract

Temperature (T) dependence of 59Co-NMR Knight shifts K of Na0.3CoO2.1.3H2O has been studied, where samples of randomly oriented powder and aligned crystals have been used for the applied magnetic fields H // ab plane and H //c-axis, respectively. For both directions of H, the shift K decreases below the superconducting transition temperature Tc(H) with decreasing T, indicating that the superconducting electron pairs are in the singlet state. The upper critical fields Hc2(T) determined from the K(H)-T curves are found to be consistent with the values reported by the resistivity measurements for both directions of H.