2009/10/31 by J. K. Dong, S. Y. Zhou, T. Y. Guan +7
Physics and Astronomy · #cond-mat.supr-con #cond-mat.str-el
paper · pdf · doi:10.1103/physrevlett.104.087005
published as Phys. Rev. Lett. 104, 087005 (2010) · 4 pages, 4 figures - replaces arXiv:0909.4855
arxiv created 2010/03/01 · arxiv updated 2013/05/29
The in-plane resistivity ρ and thermal conductivity κ of FeAs-based superconductor KFe2As2 single crystal were measured down to 50 mK. We observe non-Fermi-liquid behavior ρ(T) ∼ T1.5 at Hc2 = 5 T, and the development of a Fermi liquid state with ρ(T) ∼ T2 when further increasing field. This suggests a field-induced quantum critical point, occurring at the superconducting upper critical field Hc2. In zero field there is a large residual linear term κ0/T, and the field dependence of κ0/T mimics that in d-wave cuprate superconductors. This indicates that the superconducting gaps in KFe2As2 have nodes, likely d-wave symmetry. Such a nodal superconductivity is attributed to the antiferromagnetic spin fluctuations near the quantum critical point.