title: Measurement of a sign-changing two-gap superconducting phase in electron-doped Ba(Fe(1-x)Co(x))2As2 single crystals using scanning tunneling spectroscopy.
abstract: Scanning tunneling spectroscopic studies of Ba(Fe(1-x)Co(x))(2)As(2) (x=0.06, 0.12) single crystals reveal direct evidence for predominantly two-gap superconductivity. These gaps decrease with increasing temperature and vanish above the superconducting transition T(c). The two-gap nature and the slightly doping- and energy-dependent quasiparticle scattering interferences near the wave vectors (±π, 0) and (0, ±π) are consistent with sign-changing s-wave superconductivity. The excess zero-bias conductance and the large gap-to-T(c) ratios suggest dominant unitary impurity scattering.
authors.affiliation: Department of Physics, California Institute of Technology, Pasadena, California 91125, USA.
authors.forename: M L
authors.initials: ML
authors.lastname: Teague
authors.forename: G K
authors.initials: GK
authors.lastname: Drayna
authors.forename: G P
authors.initials: GP
authors.lastname: Lockhart
authors.forename: P
authors.initials: P
authors.lastname: Cheng
authors.forename: B
authors.initials: B
authors.lastname: Shen
authors.forename: H-H
authors.initials: HH
authors.lastname: Wen
authors.forename: N-C
authors.initials: NC
authors.lastname: Yeh