Are the iron pnictides quantum critical?

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.