Co-concentration dependence of the London penetration depth in single crystals of Ba(Fe$_{1-x}$Co$_x$)$_2$As$_2$

ORAL

Abstract

The in-plane London penetration depth, $\lambda_{ab}$(T), has been measured in single crystals of Ba(Fe$_{1-x}$Co$_x$)$_2$As$_2$ for several values of $x$ using a tunnel diode resonator (TDR) technique. The low temperature behavior of the variation of the penetration depth follows a clear power law behavior, $\Delta\lambda$(T) $\propto$ T$^n$, for all measured Co concentrations with n varying between 2 on the underdoped side to about 2.5 at the optimal doping. This non-exponential behavior in $\Delta\lambda$ indicates the existence of a significant number of superconducting quasiparticles, which is characteristic of a superconducting gap function possessing some type of nodal structure. The overal change in the superfluid density as a function of doping will be discussed. R. T. Gordon $\textit{et al.}$ arXiv:0810.2295 (2008).

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Authors

  • C. Martin

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

  • R.T. Gordon

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

  • H. Kim

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

  • M.A. Tanatar

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

  • N. Ni

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

  • S.L. Bud'ko

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

  • P.C. Canfield

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

  • J. Schmalian

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

  • R. Prozorov

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