Pressure-induced shift of T_c in K_xSr_1−xFe₂As₂ (x=0.2,0.4,0.7): Analogy to the high-T_c cuprate superconductors

The systematic pressure shifts of T_c were investigated in the whole phase diagram of the FeAs-based superconducting compound K_xSr_1−xFe₂As₂. Different regions, arising from corresponding responses of T_c to pressure (dT_c/dp>0, ≃0, or <0), can be clearly distinguished. This reveals an interesting similarity of the FeAs superconductors and the high-T_c cuprates. This behavior is a manifestation of the layered structure of the FeAs compounds and the pressure-induced charge transfer between the (Fe₂As₂) and (K/Sr) layers. The coexistence of superconductivity and spin-density wave behavior were also observed, and the pressure effects on the latter is explored.