Pressure-induced insulator-to-metal transition in the van der Waals compound CoPS3

Abstract

We have studied the insulator-to-metal transition and crystal structure evolution under high pressure in the van der Waals compound ${\mathrm{CoPS}}_{3}$ through in situ electrical resistance, Hall resistance, magnetoresistance, x-ray diffraction, and Raman scattering measurements. ${\mathrm{CoPS}}_{3}$ exhibits a $C2/m\ensuremath{\rightarrow}P\overline{3}$ structural transformation at 7 GPa accompanied by a $2.9%$ reduction in the volume per formula unit. Concomitantly, the electrical resistance decreases significantly and ${\mathrm{CoPS}}_{3}$ becomes metallic. This metallic ${\mathrm{CoPS}}_{3}$ is a hole-dominant conductor with multiple conduction bands. The linear magnetoresistance and the small volume collapse at the metallization suggest the incomplete high-spin $\ensuremath{\rightarrow}$ low-spin transition in the metallic phase. Thus, the metallic ${\mathrm{CoPS}}_{3}$ possibly possesses an inhomogeneous magnetic moment distribution and short-range magnetic ordering. This paper summarizes the comprehensive phase diagram of $M{\mathrm{PS}}_{3}$ ($M\phantom{\rule{4pt}{0ex}}=\phantom{\rule{4pt}{0ex}}\mathrm{V}$, Mn, Fe, Co, Ni, and Cd) that metalize under pressures.