Heat capacity jump at Tc and pressure derivatives of superconducting transition temperature in the Ba1−x</ma... (original) (raw)

We present the evolution of the initial (up to ∼ 10 kbar) hydrostatic, pressure dependencies of T c and of the ambient pressure jump in the heat capacity associated with the superconducting transition as a function of Na-doping in the Ba 1−x Na x Fe 2 As 2 family of iron-based superconductors. For Na concentrations 0.15 ≤ x ≤ 0.9, the jump in specific heat at T c , ∆C p | Tc , follows the ∆C p ∝ T 3 scaling found for most BaFe 2 As 2-based superconductors. Pressure dependencies are nonmonotonic for x = 0.2 and x = 0.24. For other Na concentrations T c decreases under pressure in almost linear fashion. The anomalous behavior of the x = 0.2 and x = 0.24 samples under pressure are possibly due to the crossing of the phase boundaries of the narrow antiferromagnetic tetragonal phase, unique for the Ba 1−x Na x Fe 2 As 2 series, with the application of pressure.