title: Angle-resolved photoemission spectroscopy of the iron-chalcogenide superconductor Fe1.03Te0.7Se0.3: strong coupling behavior and the universality of interband scattering.
abstract: We have performed angle-resolved photoemission spectroscopy of the iron-chalcogenide superconductor Fe1.03Te0.7Se0.3 to investigate the electronic structure relevant to superconductivity. We observed a holelike Fermi surface (FS) and an electronlike FS at the Brillouin zone center and corner, respectively, which are nearly nested by the Q∼(π,π) wave vector. We do not find evidence for the nesting instability with Q∼(π+δ,0) reminiscent of the antiferromagnetic order in the parent compound Fe1+yTe. We have observed an isotropic superconducting (SC) gap along the holelike FS with the gap size Δ of ∼4 meV (2Δ/kBTc ∼ 7), demonstrating the strong-coupling superconductivity. The observed similarity of low-energy electronic excitations between iron-chalcogenides and iron-arsenides strongly suggests that common interactions which involve Q∼(π,π) scattering are responsible for the SC pairing.
authors.affiliation: Department of Physics, Tohoku University, Sendai 980-8578, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Nakayama
authors.forename: T
authors.initials: T
authors.lastname: Sato
authors.forename: P
authors.initials: P
authors.lastname: Richard
authors.forename: T
authors.initials: T
authors.lastname: Kawahara
authors.forename: Y
authors.initials: Y
authors.lastname: Sekiba
authors.forename: T
authors.initials: T
authors.lastname: Qian
authors.forename: G F
authors.initials: GF
authors.lastname: Chen
authors.forename: J L
authors.initials: JL
authors.lastname: Luo
authors.forename: N L
authors.initials: NL
authors.lastname: Wang
authors.forename: H
authors.initials: H
authors.lastname: Ding
authors.forename: T
authors.initials: T
authors.lastname: Takahashi