The Meissner and Mesoscopic Superconducting States in the Ultrathin FeSe-Films

ORAL

Abstract

We carried out a detailed investigation on the superconductivity in eight 1-4 unit-cell FeSe-films on SrTiO3(STO) substrates by measuring their magnetization and resistivity in a field between 5E2 and 7E4 Oe over the last one and half years as a function of temperature and frequency, from 2 to 300 K and 0 to 1.5 kHz, respectively. Systematic aging effect for these samples was also well studied. The results show that samples display a complex superconducting structure, i.e. a Meissner state but populated with weak-links below 20 K, and an unusual superconducting mesostructure up to 45 K. A model is proposed to account for such a superconducting mesoscopic structure, similar to the Andreev reflection between the normal and superconducting carriers. Above 45 K, collective glass-like excitations are evident although their nature is yet to be determined.

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Authors

  • L.Z. Deng

    Texas Center for Superconductivity at the University of Houston, Texas Center for Superconductivity and Department of Physics, University of Houston

  • B. Lv

    Texas Center for Superconductivity at the University of Houston

  • Z. Wu

    Texas Center for Superconductivity at the University of Houston

  • Y.Y. Xue

    Texas Center for Superconductivity, Department of Physics, University of Houston, Texas Center for Superconductivity at the University of Houston, Texas Center for Superconductivity and Department of Physics, University of Houston

  • W. H. Zhang

    Department of Physics, Tsinghua University, Beijing

  • F. H. Li

    Department of Physics, Tsinghua University, Beijing

  • Lili Wang

    Institute of Physics, Chinese Academy of Sciences, Beijing, Tsinghua University

  • Xucun Ma

    Institute of Physics, Chinese Academy of Sciences, Beijing, Department of Physics, Tsinghua University

  • Q. K. Xue

    Tsinghua University, Department of Physics, Tsinghua University, Beijing

  • C. W. Chu

    Texas Center for Superconductivity at the University of Houston; Lawrence Berkeley National Laboratory, Berkeley, California