Quasihydrostatic versus nonhydrostatic pressure effects on the electrical properties of NiPS3

Abstract

We report combined x-ray diffraction (XRD) and electrical transport studies of the van der Waals (vdW) insulator ${\mathrm{NiPS}}_{3}$ to elucidate a pressure-induced insulator-to-metal transition (IMT). On application of quasihydrostatic pressure, two successive structural transitions occur at 10 and 29.4 GPa, as evidenced by the XRD and resistivity measurements. The concomitant IMT with a monoclinic-to-trigonal structural transition near 29.4 GPa turns out to be a common feature of the ${\mathrm{MPS}}_{3}$ family (M=transition metals). Under uniaxial-like pressure, the critical pressure for IMT is drastically reduced to $P=12.5$ GPa. These results showcase that the IMT is susceptible to strain and hydrostatic environments and that pressure offers a new venue to control a dimensional crossover in layered vdW materials.