Pressure-Induced Superconductivity at 15 K in van-der-Waals Ferroelectric CuInP2S6.

Van der Waals layered transition metal thiophosphate CuInP2S6 has attracted significant research interest due to its intriguing ferroelectric and optoelectronic properties. In this work, by combining high-pressure Raman spectroscopy, optical absorption measurements, and ab initio calculations, we uncover a cascade of pressure-induced phase transitions in CuInP2S6. Remarkably, electrical transport measurements reveal the emergence of superconductivity above 58 GPa. The superconducting transition temperature Tc increases progressively with pressure, reaching 15 K at 215 GPa─the highest Tc reported to date among the metal phosphorus trichalcogenide (MPX3) family. We attribute the origin of this high Tc in CuInP2S6 to a unique pairing mechanism characterized by dynamic carrier exchange between flat bands and highly dispersive bands dominated by sulfur vibrations. Our findings enrich the understanding of layered MPX3 materials and highlight pressure as a powerful tool for exploring high-Tc superconductivity in sulfur-based systems.