Evidence for Unconventional Superconductivity in Arsenic-Free Iron-Based Superconductor FeSe : A ^77Se-NMR Study

Abstract

We report the results of ${}^{77}$Se--nuclear magnetic resonance (NMR) in $\alpha$-FeSe, which exhibits a similar crystal structure to the LaFeAsO${}_{1-x}$F${}_x$ superconductor and shows superconductivity at 8 K. The nuclear-spin lattice relaxation rate $1/T_1$ shows $T^3$ behavior below the superconducting transition temperature $T_c$ without a coherence peak. The $T_{1}T=$ const. behavior, indicative of the Fermi liquid state, can be seen in a wide temperature range above $T_c$. The superconductivity in $\alpha$-FeSe is also an unconventional one as well as LaFeAsO${}_{1-x}$F${}_x$ and related materials. The FeAs layer is not essential for the occurrence of the unconventional superconductivity.

4pages, 4figures, to be published in J. Phys. Soc. Jpn. 77 No.11 (2008)

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• Density Functional Study of Excess Fe in Fe${}_{1+x}$Te: Magnetism and Doping
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• 75As NMR Study of Hole-Doped Superconductor Ba1-xKxFe2As2 (Tc = 38K)
• Growth and Superconductivity of FeSex Crystals
• FeTe as a candidate material for new iron-based superconductor
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• Pressure effect on superconductivity and magnetism in FeSex
• Superconductivity and Antiferromagnetism In Fe(Te1-xSx)y System