Are the iron pnictides quantum critical?

ORAL

Abstract

Unconventional superconductivity is often found in the vicinity of a doping- or pressure-induced magnetic instability, or quantum phase transition (QCP). For a pressure-induced QCP, the Gr\"{u}neisen parameter is expected to diverge as temperature approaches zero and is thus a very sensitive parameter for detecting the presence of a QCP. Experimentally, the Gr\"{u}neisen parameter can ``simply'' be determined by the ratio of the thermal expansivity to the specific heat. Here we report on high-resolution thermal expansion and specific heat measurements of Ba(Fe$_{1-x}$Co$_{x})_{2}$As$_{2}$ single crystals as a function of doping. The question of quantum criticality will be addressed by a detailed analysis of the measured thermodynamic data.

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Authors

  • Christoph Meingast

    • Karlsruhe Institute of Technology, Institute for Solid State Physics, 76021 Karlsruhe, Germany

  • Frederic Hardy

    • Karlsruhe Institute of Technology, Institute for Solid State Physics, 76021 Karlsruhe, Germany

  • Thomas Wolf

    • Karlsruhe Institute of Technology, Institute for Solid State Physics, 76021 Karlsruhe, Germany

  • Peter Adelmann

    • Karlsruhe Institute of Technology, Institute for Solid State Physics, 76021 Karlsruhe, Germany

  • Doris Ernst

    • Karlsruhe Institute of Technology, Institute for Solid State Physics, 76021 Karlsruhe, Germany

  • Peter Schweiss

    • Karlsruhe Institute of Technology, Institute for Solid State Physics, 76021 Karlsruhe, Germany

  • Rolf Heid

    • Karlsruhe Institute of Technology, Institute for Solid State Physics, 76021 Karlsruhe, Germany

  • Kai Grube

    • Karlsruhe Institute of Technology, Institute for Solid State Physics, 76021 Karlsruhe, Germany

  • Hilbert v. Loehneysen

    • Karlsruhe Institute of Technology, Institute for Solid State Physics and Physikalisches Institut, 76021 Karlsruhe, Germany