Lower critical field across the superconducting dome of Ba(Fe<sub>1-x</sub>Co<sub>x</sub>)<sub>2</sub>As<sub>2</sub> measured using optical NV-magnetometer

ORAL

Abstract

The lower critical field of superconductors (Hc1) gives direct access to the absolute value of London penetration depth which is needed to obtain the superfluid density. Hc1 is notoriously difficult to measure due to a variety of obstacles such as demagnetization, several types of surface barriers, imperfections, and anisotropies. Some of the most accurate techniques involve direct measurements of the magnetic field at which first vortices start penetrating the sample, and require outstanding sensitivity and good spatial resolution. Here we employ Nitrogen-Vacancy (NV) centers in diamond as a non-invasive, sensitive optical magnetometer to precisely measure Hc1 in single crystals of Ba(Fe1-xCox)2As2 and track it as a function of cobalt concentration (x). We discover an anomalous decrease of superfluid stiffness near x=0.057, the composition at the very edge of the magnetic phase where magnetic order becomes incommensurate. We compare our findings with similar behavior in P-doped BaFe2As2.

*This work was supported by the US DOE, Office of Science, BES Materials Science and Engineering Division under contract # DE-AC02-07CH11358.

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Presenters

  • Kamal Joshi

    • Ames Lab
    • Ames Laboratory

Authors

  • Kamal Joshi

    • Ames Lab
    • Ames Laboratory

  • Naufer Nusran

    • Ames Lab
    • Ames Laboratory

  • Kyuil Cho

    • Ames Laboratory and Department of Physics & Astronomy, Iowa State University
    • Ames Laboratory
    • Ames Laboratory and Iowa state University

  • Makariy Tanatar

    • Iowa State University and Ames Laboratory
    • Ames Laboratory and Department of Physics & Astronomy, Iowa State University
    • Ames Laboratory
    • Ames Laboratory and Iowa state University
    • Iowa State University

  • Sergey Budko

    • Ames Laboratory and Iowa State University
    • Ames Laboratory, Iowa State University
    • Dept. of Physics and Astronomy, Ames Laboratory/Iowa State University
    • Ames Laboratory and Iowa State Univ
    • Iowa State University
    • Ames Laboratory

  • Paul Canfield

    • Ames Laboratory and Iowa State University
    • Ames Laboratory, Iowa State University
    • Department of Physics and Astronomy, Iowa State University
    • Dept. of Physics and Astronomy, Ames Laboratory/Iowa State University
    • Iowa state university/Ames Laboratory
    • Ames Laboratory and Iowa State Univ
    • Iowa State University and Ames Laboratory
    • Iowa State University/Ames Laboratory
    • Iowa State University
    • Iowa State University / Ames Laboratory
    • Dept. of Physics, Iowa State Univ
    • Ames Lab
    • Ames Laboratory U.S. DOE and Department of Physics and Astronomy, Iowa State University
    • Iowa State Univ
    • Ames Laboratory
    • Department of Physics and Astronomy, Ames Laboratory and Iowa State University

  • Ruslan Prozorov

    • Ames Lab
    • Iowa State University and Ames Laboratory
    • Ames Laboratory and Department of Physics & Astronomy, Iowa State University
    • Ames Laboratory
    • Ames Laboratory and Iowa state University
    • Ames Laboratory U.S. DOE and Department of Physics and Astronomy, Iowa State University