Heat capacity jump atTcand pressure derivatives of superconducting transition temperature in the Ba1−xKxFe2As2(0.2≤x≤1.0) series

Abstract

We present the evolution of the initial (up to $\ensuremath{\sim}$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 K doping in the Ba${}_{1\ensuremath{-}x}$K${}_{x}$Fe${}_{2}$As${}_{2}$ family of iron-based superconductors. The pressure derivatives show a weak but distinct anomaly near $x\ensuremath{\sim}0.7$. In the same concentration region, $\ensuremath{\Delta}{C}_{p}{|}_{{T}_{c}}$ deviates from the $\ensuremath{\Delta}{C}_{p}\ensuremath{\propto}{T}^{3}$ scaling found for most BaFe${}_{2}$As${}_{2}$-based superconductors. These results are consistent with a possible significant modification of the superconducting state, occurring near $x\ensuremath{\sim}0.7$.