Possible Multiple Gap Superconductivity with Line Nodes in Heavily Hole-Doped Superconductor KFe2As2 Studied by 75As-NQR and Specific Heat

H. Fukazawa; Y. Yamada; K. Kondo; T. Saito; Y. Kohori; K. Kuga; Y. Matsumoto; S. Nakatsuji; H. Kito; P. M. Shirage; K. Kihou; N. Takeshita; C. -H. Lee; A. Iyo; H. Eisaki

doi:10.1143/jpsj.78.083712

arXiv · 0906.4644

Possible Multiple Gap Superconductivity with Line Nodes in Heavily Hole-Doped Superconductor KFe2As2 Studied by 75As-NQR and Specific Heat

H. Fukazawa·Y. Yamada·K. Kondo·T. Saito·Y. Kohori·K. Kuga·Y. Matsumoto·S. Nakatsuji·H. Kito·P. M. Shirage·K. Kihou·N. Takeshita·C. -H. Lee·A. Iyo·H. Eisaki

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Abstract

We report the 75As nuclear quadrupole resonance (NQR) and specific heat measurements of the heavily hole-doped superconductor KFe2As2 (Tc = 3.5 K). The spin-lattice relaxation rate 1/T1 in the superconducting state exhibits quite gradual temperature dependence with no coherence peak below Tc. The quasi-particle specific heat C_QP/T shows small specific heat jump which is about 30% of electronic specific heat coefficient just below Tc. In addition, it suggests the existence of low-energy quasi-particle excitation at the lowest measurement temperature T = 0.4 K \simeq Tc/10. These temperature dependence of 1/T1 and C_QP/T can be explained by multiple nodal superconducting gap scenario rather than multiple fully-gapped s_\pm-wave one within simple gap analysis.

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H. Fukazawa, Y. Yamada, K. Kondo, T. Saito, Y. Kohori, K. Kuga, Y. Matsumoto, S. Nakatsuji, H. Kito, P. M. Shirage, K. Kihou, N. Takeshita, C. -H. Lee, A. Iyo, H. Eisaki. 2009-06-25. Possible Multiple Gap Superconductivity with Line Nodes in Heavily Hole-Doped Superconductor KFe2As2 Studied by 75As-NQR and Specific Heat. https://doi.org/10.1143/jpsj.78.083712

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