title: Fermi surface dichotomy of the superconducting gap and pseudogap in underdoped pnictides.
abstract: High-temperature superconductivity in iron-arsenic materials (pnictides) near an antiferromagnetic phase raises the possibility of spin-fluctuation-mediated pairing. However, the interplay between antiferromagnetic fluctuations and superconductivity remains unclear in the underdoped regime, which is closer to the antiferromagnetic phase. Here we report that the superconducting gap of underdoped pnictides scales linearly with the transition temperature, and that a distinct pseudogap coexisting with the superconducting gap develops on underdoping. This pseudogap occurs on Fermi surface sheets connected by the antiferromagnetic wavevector, where the superconducting pairing is stronger as well, suggesting that antiferromagnetic fluctuations drive both the pseudogap and superconductivity. Interestingly, we found that the pseudogap and the spectral lineshape vary with the Fermi surface quasi-nesting conditions in a fashion that shares similarities with the nodal-antinodal dichotomous behaviour observed in underdoped copper oxide superconductors.
authors.affiliation: Department of Physics, Boston College, Chestnut Hill, Massachusetts 02467, USA.
authors.forename: Y M
authors.initials: YM
authors.lastname: Xu
authors.forename: P
authors.initials: P
authors.lastname: Richard
authors.forename: K
authors.initials: K
authors.lastname: Nakayama
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: M
authors.initials: M
authors.lastname: Neupane
authors.forename: S
authors.initials: S
authors.lastname: Souma
authors.forename: T
authors.initials: T
authors.lastname: Sato
authors.forename: T
authors.initials: T
authors.lastname: Takahashi
authors.forename: H Q
authors.initials: HQ
authors.lastname: Luo
authors.forename: H H
authors.initials: HH
authors.lastname: Wen
authors.forename: G F
authors.initials: GF
authors.lastname: Chen
authors.forename: N L
authors.initials: NL
authors.lastname: Wang
authors.forename: Z
authors.initials: Z
authors.lastname: Wang
authors.forename: Z
authors.initials: Z
authors.lastname: Fang
authors.forename: X
authors.initials: X
authors.lastname: Dai
authors.forename: H
authors.initials: H
authors.lastname: Ding
mesh_terms: D001152:Arsenicals / Q000737:chemistry*; D004553:Electric Conductivity; D006358:Hot Temperature; D007501:Iron / Q000737:chemistry*; D008280:Magnetics; D056951:Photoelectron Spectroscopy
chemical_list: D001152:Arsenicals; D007501:Iron