${}^{75}$As NQR and NMR studies of superconductivity and electron correlations in iron arsenide Li${}_x$FeAs

Abstract

We report the ${}^{75}$As-NQR and NMR studies on the iron arsenide superconductor Li${}_x$FeAs with $T_{\mathrm{c}}\sim 17$ K. The spin lattice relaxation rate, $1/T_1$, decreases below $T_{\mathrm{c}}$ without a coherence peak, and can be fitted by gaps with s${}^{\pm }$-wave symmetry in the presence of impurity scattering. In the normal state, both $1/T_{1}T$ and the Knight shift decrease with decreasing temperature but become constant below $T\le 50K$. Estimate of the Korringa ratio shows that the spin correlations are weaker than that in other families of iron arsenides, which may account for the lower $T_{\mathrm{c}}$ in this material.

10 pages 6 figures. to appear in J. Phys. Soc. Jpn., Vol.79, No.8

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• Possible Superconducting Symmetry and Magnetic Correlations in K0.8Fe2Se2: A 77Se-NMR Study
• Anomalous superconducting state in LiFeAs implied by the ${}^{75}$As Knight shift measurement
• Superconductivity and normal state properties of single-crystalline Tl0.47Rb0.34Fe1.63Se2 as seen via 77Se and 87Rb NMR
• Enhanced anisotropic spin fluctuations below tetragonal-to-orthorhombic transition in LaFeAs(O_{1-x}F_x) probed by ^{75}As and ^{139}La NMR
• Magnetism and superconductivity in Sr${}_2$VFeAsO${}_3$ revealed by ${}^{75}$As- and ${}^{51}$V-NMR under elevated pressures
• NMR Investigation of the iron-based superconductors Ca4(Mg,Ti)3Fe2As2O8-y and Ca5(Sc,Ti)4Fe2As2O11-y
• Multiple Superconducting Gaps, Anisotropic Spin Fluctuations and Spin-Orbit Coupling in Iron-Pnictides
• Weak Spin Fluctuation with Finite Wave Vector and Superconducting Gap Symmetry in KxFe2-ySe2: 77Se Nuclear Magnetic Resonance
• Effect of inelastic scattering on the nuclear magnetic relaxation rate 1/T1T in iron-based superconductors
• 31P NMR Investigation of the Superconductor LiFeP (Tc = 5 K)