Pressure-Induced Mott Transition Followed by a 24-K Superconducting Phase in BaFe2 S3

We performed high-pressure study for a Mott insulator BaFe2S3, by measuring dc resistivity and ac susceptibility up to 15 GPa. We found that the antiferromagnetic insulating state at the ambient pressure is transformed into a metallic state at the critical pressure, Pc=10 GPa, and the superconductivity with the optimum Tc=24 K emerges above Pc. Furthermore, we found that the metal-insulator transition (Mott transition) boundary terminates at a critical point around 10 GPa and 75 K. The obtained pressure-temperature (P-T) phase diagram is similar to those of the organic and fullerene compounds; namely, BaFe2S3 is the first inorganic superconductor in the vicinity of bandwidth control type Mott transition.