Nodeless energy gaps of single-crystalline Ba0.68K 0.32Fe2As2 as seen via As75 NMR

Z. Li, D. L. Sun, C. T. Lin, Y. H. Su, J. P. Hu, Guo Qing Zheng

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Abstract

We report As75 nuclear magnetic resonance studies on a very clean hole-doped single-crystal Ba0.68K0.32Fe2As 2 (Tc=38.5 K). The spin-lattice relaxation rate 1/T 1 shows an exponential decrease below T0.45Tc down to T0.11Tc, which indicates a fully opened energy gap. From the ratio (T1)c/(T1)a, where a and c denote the crystal directions, we find that the antiferromagnetic spin fluctuation is anisotropic in the spin space above Tc. The anisotropy decreases below Tc and disappears at T→0. We argue that the anisotropy stems from spin-orbit coupling whose effect vanishes when spin-singlet electron pairs form with a nodeless gap.

Original languageEnglish
Article number140506
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume83
Issue number14
DOIs
Publication statusPublished - Apr 18 2011

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ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics

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