Structural and electronic phase transitions in FePS$₃$ under the application of pressure

Two-dimensional materials have proven to be a prolific breeding ground of new and unstudied forms of magnetism and unusual metallic states, particularly when tuned between their insulating and metallic phases. In this paper we present work on a new metal to insulator transition system FePS$₃$ . This compound is a two-dimensional van-der-Waals antiferromagnetic Mott insulator. Here we report the discovery of an insulator-metal transition in FePS$₃$, as evidenced by x-ray diffraction and electrical transport measurements, using high pressure as a tuning parameter. Two structural phase transitions are observed in the x-ray diffraction data as a function of pressure and resistivity measurements show evidence of onset of a metallic state at high pressures. We propose models for the two new structures that can successfully explain the x-ray diffraction patterns.