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arXiv · 1101.5014

Multiple superconducting gap and anisotropic spin fluctuations in iron arsenides: Comparison with nickel analog

Z. Li·S. Kawasaki·T. Oka·T. Tabuchi·Y. Ooe·M. Ichioka·Z. A. Ren·Z. X. Zhao·J. L. Luo·N. L. Wang·X. C. Wang·Q. Q. Liu·C. Q. Jin·C. T. Lin·Guo-qing Zheng
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Abstract

We present extensive 75As NMR and NQR data on the superconducting arsenides PrFeAs0.89F0.11 (Tc=45 K), LaFeAsO0.92F0.08 (Tc=27 K), LiFeAs (Tc = 17 K) and Ba0.72K0.28Fe2As2 (Tc = 31.5 K) single crystal, and compare with the nickel analog LaNiAsO0.9F0.1 (Tc=4.0 K) . In contrast to LaNiAsO0.9F0.1 where the superconducting gap is shown to be isotropic, the spin lattice relaxation rate 1/T1 in the Fe-arsenides decreases below Tc with no coherence peak and shows a step-wise variation at low temperatures. The Knight shift decreases below Tc and shows a step-wise T variation as well. These results indicate spinsinglet superconductivity with multiple gaps in the Fe-arsenides. The Fe antiferromagnetic spin fluctuations are anisotropic and weaker compared to underdoped copper-oxides or cobalt-oxide superconductors, while there is no significant electron correlations in LaNiAsO0.9F0.1. We will discuss the implications of these results and highlight the importance of the Fermi surface topology.

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Z. Li, S. Kawasaki, T. Oka, T. Tabuchi, Y. Ooe, M. Ichioka, Z. A. Ren, Z. X. Zhao, J. L. Luo, N. L. Wang, X. C. Wang, Q. Q. Liu, C. Q. Jin, C. T. Lin, Guo-qing Zheng. 2011-01-26. Multiple superconducting gap and anisotropic spin fluctuations in iron arsenides: Comparison with nickel analog. https://doi.org/10.1016/j.jpcs.2010.10.038

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