Surface geometric and electronic structures of A(Fe, Co)$_{2}$As$_{2}$ (A=Ba,Ca)

ORAL

Abstract

We utilize Low Energy Electron Diffraction (LEED) to determine the surface structure combined with real-space scanning tunneling microcopy/spectroscopy (STM/STS), to investigate the local geometric and electronic structures at the (001) surface of the compounds of AFe$_{2}$As$_{2}$ (A= Ba, Ca). In general two competing surface reconstructions are observed with either a 1x2 or a ($\surd $2x$\surd $2)R45$^{\circ}$ (tetragonal notation) structure. The ($\surd $2x$\surd $2)R45$^{\circ}$ structure corresponds to the 1x1 orthorhombic phase. While the ($\surd $2x$\surd $2)R45$^{\circ}$ phase always present for A=Ba, the 1x2 structure dominates for A=Ca. We will discuss the detailed structural change with Co doping, thermal cycling, contamination, electron beam induced damage, and cleaving temperature. Specifically, 1x2 phase is sensitive to the thermal processing, with indications of a temperature dependence phase transition. *Supported by NSF DMR-1002622

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Authors

  • Guorong Li

    • Louisiana State University, Baton Rouge, LA 70803, USA
    • Dept. of Physics, Louisiana State University, Baton Rouge, LA 70802, USA
    • Louisiana State University

  • V.B. Nascimento

    • Louisiana State University, Baton Rouge LA
    • Dept. of Physics, Louisiana State University, Baton Rouge, LA 70802, USA

  • Xiaobo He

    • Louisiana State University, Baton Rouge, LA 70803, USA
    • Dept. of Physics, Louisiana State University, Baton Rouge, LA 70802, USA

  • Amar Karki

    • Dept. of Physics, Louisiana State University, Baton Rouge, LA 70802, USA
    • Louisiana State University

  • Jiandi Zhang

    • Louisiana State University, Baton Rouge, LA 70803, USA
    • Dept. of Physics, Louisiana State University, Baton Rouge, LA 70802, USA
    • Louisiana State University

  • Rongying Jin

    • Louisiana State University
    • Louisiana State University, Baton Rouge, LA 70803, USA
    • Department of Physics and Astronomy, Louisiana State University
    • Louisiana State University, Baton Rouge LA
    • Louisiana State University, USA
    • Dept. of Physics, Louisiana State University, Baton Rouge, LA 70802, USA

  • A.S. Sefat

    • ORNL
    • Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
    • Oak Ridge National Laboratory
    • MST Division, Oak Ridge National Laboratory
    • ORNL, Oak Ridge, TN
    • Oak Ridge National Laboratory (ORNL), Oak Ridge, TN 37831, USA
    • Materials Science \& Technology Division, ORNL, Oak Ridge, TN 37831, USA

  • M.A. McGuire

    • ORNL
    • Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
    • Oak Ridge National Laboratory
    • Materials Science \& Technology Division, ORNL, Oak Ridge, TN 37831, USA

  • B.C. Sales

    • ORNL
    • Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
    • Oak Ridge National Laboratory
    • Oak Ridge National Laboratory (ORNL), Oak Ridge, TN 37831, USA
    • Materials Science \& Technology Division, ORNL, Oak Ridge, TN 37831, USA

  • D. Mandrus

    • University of Tennessee and Oak Ridge National Laboratory
    • Univ of Tenn, Oak Ridge Natl Lab
    • Dept. of Materials Science \& Engineering, The University of Tennessee, Knoxville, TN, 37996, USA

  • Ward Plummer

    • Louisiana State University, Baton Rouge, LA 70803, USA
    • Louisiana State University
    • Department of Physics and Astronomy, Louisiana State University
    • Louisiana State University, Baton Rouge LA
    • Depart. of Physics, Louisiana State University, Baton Rouge, LA 70802, USA