Quantum critical regime in the phase diagram of K$_x$Sr$_{1-x}$Fe$_2$As$_2$

ORAL

Abstract

The electrical and thermoelectric properties of K$_x$Sr$_{1-x}$Fe$_2$As$_2$ are investigated. While the temperature dependence of the resistivity of SrFe$_2$As$_2$ (x=0) and KFe$_2$As$_2$ (x=1) is strongly nonlinear over a large temperature range it becomes surprisingly linear for x close to x$_c$ = 0.4 above the superconducting transition. This apparent deviation from the Fermi liquid behavior is similar to the high-T$_c$ cuprate superconductors and may indicate the existence of a quantum critical regime above the superconducting dome. We show that the temperature dependence of the thermoelectric power S follows a logarithmic scaling, S/T = const.*log(T) at the critical value x$_c$. The experimental results are consistent with a Ginzburg-Landau model for FeAs compounds predicting quantum critical scaling with a dynamical exponent z=2 and an effective dimension d+z=4.

*This work is supported by the T.L.L. Temple Foundation, the J.J. and R. Moores Endowment, the State of Texas through TCSUH, the DoE, the NSF, and the R. A. Welch Foundation.

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Authors

  • Bernd Lorenz

    • TCSUH and Department of Physics, University of Houston, Houston, Texas 77204-5002, USA
    • TCSUH and Dept. of Physics, University of Houston
    • Texas Center for Superconductivity at the University of Houston and Department of Physics
    • TCSUH and Department of Physics, University of Houston, Houston, Texas 77204, USA

  • Melissa Gooch

    • TCSUH and Dept. of Physics, University of Houston

  • Bing Lv

    • TCSUH and Dept. of Chemistry, University of Houston

  • Arnold M. Guloy

    • TCSUH and Dept. of Chemistry, University of Houston

  • Ching-Wu Chu

    • TCSUH and Dept. of Physics, University of Houston