Thermal expansion and Gr\"uneisen parameters of Ba(Fe1-xCox)2As2 - a   thermodynamic quest for quantum criticality
  Thermal expansion data are used to study the uniaxial pressure dependence of the electronic/magnetic entropy of Ba(Fe1-xCox)2As2. Uniaxial pressure is found to be proportional to doping and, thus, also an appropriate tuning parameter in this system. Many of the features predicted to occur for a pressure-tuned quantum critical system, in which superconductivity is an emergent phase hiding the critical point, are observed. The electronic/magnetic Gr\"uneisen parameters associated with the spin-density wave and superconducting transitions further demonstrate an intimate connection between both ordering phenomena. 
Christoph Meingast, Fr\'ed\'eric Hardy, Rolf Heid, Peter Adelmann,   Anna B\"ohmer, Philipp Burger, Doris Ernst, Rainer From...
cond-mat.supr-con cond-mat.str-el