Effect of doping on the crystalline structure and superconductivity properties in Ca$_{1-x}$Na$_{x}$Fe$_{2}$As$_{2 }$ single crystals

ORAL

Abstract

We have studied the crystalline structure and the superconducting properties of Ca$_{1-x}$Na$_{x}$Fe$_{2}$As$_{2}$ single crystals for various levels of the chemical doping (x). We performed a comparative analysis of the angular dependent $H_{c2}(\Theta )$ (where $\Theta $ is the angle between the magnetic field and the c axis) for x$\sim $0.5 and x $\sim $ 0.75, corresponding to T$_{c} \quad \sim $ 19 K and 33 K, respectively. We found that in both cases $H_{c2}(\Theta )$ near T$_{c}$ exhibits a single band character with the same anisotropy $\gamma \quad \sim $ 1.8. In the crystal with T$_{c} \quad \sim $ 33 K we detected the presence of a narrow vortex-liquid phase, in agreement with the expectation from estimates based on the Lindemann criterion and the Ginzburg number. We also found large and anisotropic flux creep rates, with temperature dependences that indicate glassy relaxation. We analyzed those results in terms of single vortex and collective pinning regimes associated with random and correlated disorder.

*Research supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering.

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Authors

  • L. Civale

    • Los Alamos National Laboratory, Los Alamos, NM, USA
    • Los Alamos National Laboratory, NM 87544
    • Superconductivity Technology Center, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA

  • N. Haberkorn

    • Los Alamos National Laboratory, Los Alamos, NM, USA
    • Superconductivity Technology Center, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA

  • B. Maiorov

    • Los Alamos National Laboratory, Los Alamos, NM, USA
    • Los Alamos National Laboratory, NM 87544
    • Superconductivity Technology Center, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA

  • Marcelo Jaime

    • Los Alamos National Laboratory, Los Alamos, NM, USA
    • LANL
    • NHMFL-Los Alamos
    • MPA-CMMS, Los Alamos National Laboratory, Los Alamos, NM 87545, USA
    • NHMFL, Los Alamos National Laboratory, Los Alamos NM 87545, USA

  • G. Chen

    • Renmin University of China, Beijing, China

  • W. Yu

    • Renmin University of China, Beijing, China