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

doi:10.1103/PhysRevB.83.140506

Nodeless energy gaps of single-crystalline Ba_0.68K _0.32Fe₂As₂ as seen via As75 NMR

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

Research output: Contribution to journal › Article › peer-review

58 Citations (Scopus)

Abstract

We report As75 nuclear magnetic resonance studies on a very clean hole-doped single-crystal Ba_0.68K_0.32Fe₂As ₂ (T_c=38.5 K). The spin-lattice relaxation rate 1/T ₁ shows an exponential decrease below T0.45T_c down to T0.11T_c, 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 T_c. The anisotropy decreases below T_c 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 language	English
Article number	140506
Journal	Physical Review B - Condensed Matter and Materials Physics
Volume	83
Issue number	14
DOIs	https://doi.org/10.1103/PhysRevB.83.140506
Publication status	Published - Apr 18 2011

ASJC Scopus subject areas

Electronic, Optical and Magnetic Materials
Condensed Matter Physics

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

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.",

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T1 - Nodeless energy gaps of single-crystalline Ba0.68K 0.32Fe2As2 as seen via As75 NMR

AU - Li, Z.

AU - Sun, D. L.

AU - Lin, C. T.

AU - Su, Y. H.

AU - Hu, J. P.

AU - Zheng, Guo Qing

PY - 2011/4/18

Y1 - 2011/4/18

N2 - 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.

AB - 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.

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Nodeless energy gaps of single-crystalline Ba_0.68K _0.32Fe₂As₂ as seen via As75 NMR

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