Maze-like surface reconstruction on pure SrFe$_2$As$_2$ observed by STM/STS

ORAL

Abstract

We measured undoped SrFe$_2$As$_2$ samples using a low temperature scanning tunneling microscope. Similar samples showed superconductivity in up to 15\% of its volume in measurements of the diamagnetic screening although being undoped as confirmed by energy dispersive x-ray spectroscopy. The samples where cleaved at room temperature at a pressure $P<10^{-8}$ mbar before introducing them into the low temperature scanning tunneling microscope (LTSTM) operating at a temperature of $T=4.2$ K. Beside the usual striped surface reconstruction and disordered regions we observed areas showing a maze like reconstruction. Atomically resolved images strongly suggest that the maze structure is formed by adatoms and thus, by inference, is the striped phase. Scanning tunneling spectroscopy (STS) measurements showed a superconducting gap on both the striped and maze phase of the sample, similar to the spectra on a cobalt doped sample. The results will be discussed in detail.

*Funded in part by the Laboratory for Physical Sciences.

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Authors

  • Michael Dreyer

    • University of Maryland
    • Physics Department, University of Maryland and Laboratory for Physical Sciences

  • Mark Gubrud

    • University of Maryland

  • Hui Wang

    • University of Maryland

  • Shanta Saha

    • Center for Nanophysics and Advanced Materials, Department of Physics, University of Maryland, College Park, MD
    • Center for Nano Physics and Advanced Materials, Department of Physics, University of Maryland, College Park, MD
    • University of Maryland at College Park
    • University of Maryland

  • Nick Butch

    • Center for Nanophysics and Advanced Materials, U. of Maryland
    • Center for Nanophysics and Advanced Materials, Department of Physics, University of Maryland, College Park, MD
    • Center for Nano Physics and Advanced Materials, Department of Physics, University of Maryland, College Park, MD
    • Department of Physics, University of Maryland
    • Center for Nanophysics and Advanced Materials, Department of Physics, University of Maryland, College Park
    • University of Maryland
    • Center for Nanophysics \& Advanced Materials and Department of Physics, University of Maryland, College Park, MD 20742, USA

  • Kevin Kirshenbaum

    • Center for Nanophysics and Advanced Materials, Department of Physics, University of Maryland, College Park, MD
    • Center for Nanophysics \& Advanced Materials and Department of Physics, University of Maryland, College Park, MD 20742, USA
    • University of Maryland

  • Johnpierre Paglione

    • Center for Nanophysics and Advanced Materials, U. of Maryland
    • University of Maryland
    • Center for Nanophysics and Advanced Materials, Department of Physics, University of Maryland, College Park, MD
    • Center for Nano Physics and Advanced Materials, Department of Physics, University of Maryland, College Park, MD
    • Department of Physics, University of Maryland
    • University of Maryland at College Park
    • Center for Nanophysics \& Advanced Materials and Department of Physics, University of Maryland, College Park, MD 20742, USA