Measurements of the critical current of small Sr$_2$RuO$_4$ crystals

ORAL

Abstract

We report critical current measurements of chiral $p$-wave superconductor Sr$_2$RuO$_4$. Because of the strong anisotropy possessed by Sr$_2$RuO$_4$, vortex lines along the in-plane direction are expected to be pinned more strongly than those along the $c$ axis, resulting in anisotropic critical currents. We prepared small single crystals of Sr$_2$RuO$_4$ with a typical size of 50$\mu$m$\times$ 10$\mu$m$\times$1$\mu$m by mechanical exfoliation and characterized them by Raman spectroscopy and high-resolution transmission electron microscopy, showing that they were either pure Sr$_2$RuO$_4$ or eutectic phase containing one or more Ru microdomains. Four-point or Hall probes were prepared on the small crystals by photo lithography. While samples of pure Sr$_2$RuO$_4$ exhibited a typical transition temperature ($T_c$) of 1.2K, slightly lower than the optimal bulk $T_c$, 1.5K, those with Ru microdomains showed multiple resistive transitions with the highest $T_c$ around 2K. The critical current and critical field phase diagrams were determined for these small crystals. Surprisingly, the in-plane critical current density, measured for the first time, was found to be significantly larger than that along $c$-axis of the bulk. The physical implications of these observations will be discussed. Supported by DOE.

–

Authors

  • Yiqun Ying

    Department of Physics, The Pennsylvania State University

  • Neal Staley

    Department of Physics and Materials Research Institute, The Pennsylvania State University, Department of Physics, The Pennsylvania State University

  • Ying Liu

    Department of Physics and Materials Research Institute, The Pennsylvania State University, Physics Department, The Pennsylvania State University, Department of Physics, The Pennsylvania State University

  • Yan Xin

    National High Magnetic Field Laboratory, Florida State University

  • D. Fobes

    Department of Physics, Tulane University, Department of Physics and Engineering Physics, Tulane University, New Orleans, LA 70118

  • Tijiang Liu

    Department of Physics, Tulane University, Department of Physics and Engineering Physics, Tulane University, New Orleans, LA 70118, Department of Physics and Engineering Physics, Tulane University

  • Zhiqiang Mao

    Dept. of Physics, Tulane Univ., Department of Physics, Tulane University, Department of Physics and Engineering Physics, Tulane University, New Orleans, LA 70118, Department of Physics and Engineering Physics, Tulane University, New Orleans, Department of Physics and Engineering Physics, Tulane University