Synthesis and Superconductivity of New BiS2 Based Superconductor PrO0.5F0.5BiS2

We report synthesis and superconductivity at 3.7 K in PrO_0.5F_0.5BiS₂. The newly discovered material belongs to the layered sulfide based REO_0.5F_0.5BiS₂ compounds having a ZrCuSiAs-type structure. The bulk polycrystalline compound is synthesized by the vacuum encapsulation technique at 780 ^°C in a single step. Detailed structural analysis has shown that the as synthesized PrO_0.5F_0.5BiS₂ is crystallized in a tetragonal P4/nmm space group with lattice parameters a=4.015(5) Å, c=13.362(4) Å. Bulk superconductivity is observed in PrO_0.5F_0.5BiS₂ below 4 K from magnetic and transport measurements. Electrical transport measurements showed superconducting transition temperature (T _c ) onset at 3.7 K and T _c (ρ=0) at 3.1 K. The hump at T _c related to the superconducting transition is not observed in the heat capacity measurement and rather a Schottky-type anomaly is observed at below ～6 K. The compound is slightly semiconducting in a normal state. Isothermal magnetization (MH) exhibited typical type II behavior with a lower critical field (H _c1) of around 8 Oe.