Two superconducting gaps in LaFeAsO0.92F0.08 revealed by 75As nuclear quadrupole resonance

S. Kawasaki, K. Shimada, G. F. Chen, J. L. Luo, N. L. Wang, Guo Qing Zheng

Research output: Contribution to journalArticle

78 Citations (Scopus)

Abstract

We report A 75 s nuclear quadrupole resonance studies on superconducting oxypnictide LaFeAsO0.92 F0.08 (Tc =23 K). The temperature dependence of the spin-lattice relaxation rate (1/ T1) decreases below Tc without a coherence (Hebel-Slichter) peak and shows a temperature dependence that is not simple power law nor exponential. We show that the result can be understood in terms of two superconducting gaps of either d - or ±s -wave symmetry, with the larger gap Δ1 ∼4 kB Tc and the smaller one Δ2 ∼1.5 kB Tc. Our result suggests that the multiple-gap feature is universal in the oxypnictide superconductors, which is probably associated with the multiple electronic band structures in this class of materials. We also find that 1/ T1 T above Tc increases with decreasing temperature, which suggests weak magnetic fluctuations in the normal state.

Original languageEnglish
Article number220506
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume78
Issue number22
DOIs
Publication statusPublished - Dec 1 2008

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics

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