title: Phase-incoherent superconducting pairs in the normal state of Ba(Fe(1-x)Co(x))₂As₂.
abstract: The normal state properties of the recently discovered ferropnictide superconductors might hold the key to understanding their exotic superconductivity. Using point-contact spectroscopy we show that Andreev reflection between an epitaxial thin film of Ba(Fe(0.92)Co(0.08))₂As₂ and a silver tip can be seen in the normal state of the film up to temperature T∼1.3T(c), where T(c) is the critical temperature of the superconductor. Andreev reflection far above T(c) can be understood only when superconducting pairs arising from strong fluctuation of the phase of the complex superconducting order parameter exist in the normal state. Our results provide spectroscopic evidence of phase-incoherent superconducting pairs in the normal state of the ferropnictide superconductors.
authors.affiliation: Department of Physics and Astronomy, Northwestern University, Evanston, Illinois 60208, USA. g-sheet@northwestern.edu
authors.forename: Goutam
authors.initials: G
authors.lastname: Sheet
authors.forename: Manan
authors.initials: M
authors.lastname: Mehta
authors.forename: D A
authors.initials: DA
authors.lastname: Dikin
authors.forename: S
authors.initials: S
authors.lastname: Lee
authors.forename: C W
authors.initials: CW
authors.lastname: Bark
authors.forename: J
authors.initials: J
authors.lastname: Jiang
authors.forename: J D
authors.initials: JD
authors.lastname: Weiss
authors.forename: E E
authors.initials: EE
authors.lastname: Hellstrom
authors.forename: M S
authors.initials: MS
authors.lastname: Rzchowski
authors.forename: C B
authors.initials: CB
authors.lastname: Eom
authors.forename: V
authors.initials: V
authors.lastname: Chandrasekhar