First order quantum phase transition under the superconducting dome of Ba(Fe$_{\mathrm{1-x}}$Co$_{\mathrm{x}})_{2}$As$_{2}$

ORAL

Abstract

We present the results of magnetoresistivity and magnetization measurements performed under pressure (P) on single crystals of Ba(Fe$_{\mathrm{1-x}}$Co$_{\mathrm{x}})_{2}$As$_{2}$ (x $=$ 0, 0.042, 0.06, 0.08). Our results show that the antiferromagnetic phase macroscopically coexists with the superconducting phase and can be induced by the magnetic field locally nucleated in the vortex core for the x $=$ 0.06 sample. In addition, the diamagnetic signal of the x $=$ 0.06 sample shows a huge jump around P $=$ 0.5~GPa, where the superconducting transition temperature displays a maximum. This suggests that a first order antiferromagnetic quantum phase transition (QPT) is present inside the superconducting dome, and that the superconductivity in this system is closely related to this QPT. A magnetic tricritical point is observed inside the superconducting dome, and no quantum critical point is expected in zero magnetic field.

*This work was supported by NSF (DMR-1006606 and DMR-0844115), ICAM Branches Cost Sharing Fund from Institute for Complex Adaptive Matter, and Ohio Board of Regents (OBR-RIP-220573) at KSU. H.X. was supported by NSFC (11104335) and the MOST (2011CBA00102).

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Authors

  • T. Hu

    • Kent State University
    • Kent State University, USA

  • H. Xiao

    • Kent State University, USA

  • Y.P. Singh

    • Kent State University
    • Department of Physics, Kent State University, Kent, Ohio 44242
    • Kent State University, USA

  • D.J. Haney

    • Kent State University, USA

  • X.Y. Huang

    • Kent State University, USA

  • M. Dzero

    • Kent State University
    • Kent State University, USA

  • H.H. Wen

    • Nanjing University, China

  • C.C. Almasan

    • Kent State University
    • Department of Physics, Kent State University, Kent, Ohio 44242
    • Kent State University, USA