Pressure cycle of superconducting Cs_0.8Fe₂Se₂ : A transport study

We report measurements of the temperature and pressure dependence of the electrical resistivity (ρ) of single-crystalline iron-based chalcogenide Cs0.8Fe2Se2. In this material, superconductivity with a transition temperature (Tc ) ∼ 30 K develops from a normal state with extremely large resistivity. At ambient pressure, a large ‘‘hump’’ in the resistivity is observed around 200 K. Under pressure, the resistivity decreases by two orders of magnitude, concomitant with a sudden Tc suppression around pc ∼ 8 GPa. Even at 9 GPa a metallic resistivity state is not recovered, and the ρ(T ) ‘‘hump’’ is still detected. A comparison of the data measured upon increasing and decreasing the external pressure leads us to suggest that the superconductivity is not related to this hump