We report systematic 75As-NQR and L 139 a-NMR studies on nickel pnictide superconductors LaNiAsO1-x Fx (x=0, 0.06, 0.10, and 0.12). The spin-lattice relaxation rate 1/T1 decreases below Tc with a well-defined coherence peak and follows an exponential decay at low temperatures. This result indicates that the superconducting gap is fully opened and is strikingly different from that observed in iron-pnictide analogs. In the normal state, 1/T1 T is constant in the temperature range Tc ∼4 K≤T≤10 K for all compounds and up to T=250 K for x=0 and 0.06, which indicates weak electron correlations and is also different from the iron analog. We argue that the differences between the iron and nickel pnictides arise from the different electronic band structure. Our results highlight the importance of the peculiar Fermi-surface topology in iron pnictides. We also provide a possible interpretation for the "pseudogap-like" behavior in the normal state which is also seen in iron pnictides.
|Journal||Physical Review B - Condensed Matter and Materials Physics|
|Publication status||Published - Apr 28 2010|
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics