title: Role of antiferromagnetic ordering in the (1×2) surface reconstruction of Ca(Fe(1-x)Co(x))2As2.
abstract: Low energy electron diffraction, scanning tunneling microscopy and spectroscopy, and first-principles spin-dependent density functional theory are utilized to investigate the geometric, electronic, and magnetic structures of the stripe-ordered (1×2) surface of Ca(Fe1-xCox)2As2 (x=0, 0.075). The surface is terminated with a 50% Ca layer. Compared to the bulk, the surface Ca layer has a large inward relaxation (∼0.5  Å), and the underneath As-Fe2-As layer displays a significant buckling. First-principles calculations show that the (1×2) phase is stabilized by the bulk antiferromagnetic spin ordering through the spin-charge-lattice coupling. Strikingly, a superconducting gap (∼7  meV at 7.4 K) is observed to spatially coexist with the (1×2) phase (x=0.075 compound). This implies the coexistence of both superconductivity and AFM ordering at the surface.
authors.affiliation: Department of Physics & Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803, USA.
authors.forename: Guorong
authors.initials: G
authors.lastname: Li
authors.affiliation: Department of Physics, Applied Physics, and Astronomy, Rensselaer Polytechnic Institute, Troy, New York 12180, USA.
authors.forename: Liangbo
authors.initials: L
authors.lastname: Liang
authors.affiliation: Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
authors.forename: Qing
authors.initials: Q
authors.lastname: Li
authors.affiliation: Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
authors.forename: Minghu
authors.initials: M
authors.lastname: Pan
authors.affiliation: Department of Physics & Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803, USA.
authors.forename: V B
authors.initials: VB
authors.lastname: Nascimento
authors.affiliation: Department of Physics & Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803, USA.
authors.forename: Xiaobo
authors.initials: X
authors.lastname: He
authors.affiliation: Department of Physics & Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803, USA.
authors.forename: A B
authors.initials: AB
authors.lastname: Karki
authors.affiliation: Department of Physics, Applied Physics, and Astronomy, Rensselaer Polytechnic Institute, Troy, New York 12180, USA.
authors.forename: Vincent
authors.initials: V
authors.lastname: Meunier
authors.affiliation: Department of Physics & Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803, USA.
authors.forename: Rongying
authors.initials: R
authors.lastname: Jin
authors.affiliation: Department of Physics & Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803, USA.
authors.forename: Jiandi
authors.initials: J
authors.lastname: Zhang
authors.affiliation: Department of Physics & Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803, USA.
authors.forename: E W
authors.initials: EW
authors.lastname: Plummer