title: Quantum criticality and nodal superconductivity in the FeAs-based superconductor KFe2As2.
abstract: The in-plane resistivity rho and thermal conductivity kappa of the FeAs-based superconductor KFe2As2 single crystal were measured down to 50 mK. We observe non-Fermi-liquid behavior rho(T) approximately T{1.5} at H{c{2}}=5 T, and the development of a Fermi liquid state with rho(T) approximately T{2} when further increasing the field. This suggests a field-induced quantum critical point, occurring at the superconducting upper critical field H{c{2}}. In zero field, there is a large residual linear term kappa{0}/T, and the field dependence of kappa_{0}/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.
authors.affiliation: Department of Physics, Surface Physics Laboratory (National Key Laboratory), and Laboratory of Advanced Materials, Fudan University, Shanghai 200433, China.
authors.forename: J K
authors.initials: JK
authors.lastname: Dong
authors.forename: S Y
authors.initials: SY
authors.lastname: Zhou
authors.forename: T Y
authors.initials: TY
authors.lastname: Guan
authors.forename: H
authors.initials: H
authors.lastname: Zhang
authors.forename: Y F
authors.initials: YF
authors.lastname: Dai
authors.forename: X
authors.initials: X
authors.lastname: Qiu
authors.forename: X F
authors.initials: XF
authors.lastname: Wang
authors.forename: Y
authors.initials: Y
authors.lastname: He
authors.forename: X H
authors.initials: XH
authors.lastname: Chen
authors.forename: S Y
authors.initials: SY
authors.lastname: Li