Antiferromagnetic spin fluctuations above the dome-shaped and full-gap superconducting states of LaFeAsO 1-xF x revealed by As75-nuclear quadrupole resonance

T. Oka, Z. Li, S. Kawasaki, G. F. Chen, N. L. Wang, Guo Qing Zheng

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47 Citations (Scopus)

Abstract

We report a systematic study by As75 nuclear-quadrupole resonance in LaFeAsO 1-xF x. The antiferromagnetic spin fluctuation found above the magnetic ordering temperature T N=58K for x=0.03 persists in the regime 0.04≤x≤0.08, where superconductivity sets in. A dome-shaped x dependence of the superconducting transition temperature T c is found, with the highest T c=27K at x=0.06, which is realized under significant antiferromagnetic spin fluctuation. With increasing x further, the antiferromagnetic spin fluctuation decreases, and so does T c. These features resemble closely the cuprates La 2-xSr xCuO 4. In x=0.06, the spin-lattice relaxation rate (1/T 1) below T c decreases exponentially down to 0.13T c, which unambiguously indicates that the energy gaps are fully opened. The temperature variation of 1/T 1 below T c is rendered nonexponential for other x by impurity scattering.

Original languageEnglish
Article number047001
JournalPhysical Review Letters
Volume108
Issue number4
DOIs
Publication statusPublished - Jan 26 2012

ASJC Scopus subject areas

  • Physics and Astronomy(all)

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