Interplay of superconductivity with the SDW order and Eu$^{2+}$ AFM order in the Ca$_{\mathrm{1-x}}$Eu$_{\mathrm{x}}$Fe$_2$As$_2$ system at ambient and under pressures

ORAL

Abstract

Single crystals of Eu doped Ca$_{\mathrm{1-x}}$Eu$_{\mathrm{x}}$Fe$_2$As$_2$ (0$\le $ x $\le $1) with size up to 5 x 5 mm size were grown from FeAs self-flux technique. Detailed magnetic and resistivity data a systematical evolution of a spin-density-wave (SDW) transition from $\sim$ 170K at x$=$0 to $\sim$ 190K at x $=$1. Moreover, the Eu$^{2+}$ antiferromagnetic (AFM) emerged at 3.7K at a threshold doping x $\sim$ 0.2, and systematically increased up to $\sim$ 20K with the increase of the Eu content. High pressure was applied to some of these compounds to explore the competition among SDW, collapsed phase and superconductivity. Superconductivity up to 18K was observed in samples without the structural ``collapsed tetragonal'' phase before the emergence of the superconductivity signal. The data suggest that the superconductivity in the doped Ca122 under pressure is not associated with the structural collapsed-tetragonal phase. The complex phase diagram of the SDW, Eu$^{2+}$ AFM order and superconductivity at ambient and under pressure will be presented and its implication will be discussed.

*Work at Houston is supported in part by US AFOSR, the State of Texas, T. L. L. Temple Foundation and John and Rebecca Moores Endowment.

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Authors

  • Keshav Shrestha

    • Texas Center for Superconductivity and Department of Physics, University of Houston, Houston, TX 77204-5002

  • Kui Zhao

    • Texas Center for Superconductivity and Department of Physics, University of Houston, Houston, TX 77204-5002

  • Ben Jawdat

    • Texas Center for Superconductivity and Department of Physics, University of Houston, Houston, TX 77204-5002

  • Liangzi Deng

    • Texas Center for Superconductivity, University of Houston
    • Texas Center for Superconductivity and department of Physics, University of Houston, Houston, TX 77204-5002
    • Texas Center for Superconductivity and Department of Physics, University of Houston, Houston, TX 77204-5002

  • Xiyu Zhu

    • Texas Center for Superconductivity and Department of Physics, University of Houston, Houston, TX 77204-5002

  • Yuyi Xue

    • Texas Center for Superconductivity, University of Houston
    • Texas Center for Superconductivity and Department of Physics, University of Houston, Houston, TX 77204-5002

  • Bing Lv

    • Texas Center for Superconductivity and Department of Physics, University of Houston, Houston, TX 77204-5002

  • Paul Chu

    • Texas Center for Superconductivity, University of Houston
    • University of Houston
    • Texas Center for Superconductivity and Department of Physics, University of Houston, Houston, TX 77204-5002
    • Texas Center for Superconductivity and Department of Physics, University of Houston, Houston, TX 77204-5002 \& Lawrence Berkeley National Laboratory