Optical spectroscopy study of the pressure-induced transitions and high-pressure metallic phases in 2D van der Waals magnets MPX3

• Applicant: Professorin Dr. Christine Kuntscher
• Subject Area: Experimental Condensed Matter Physics
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 546152101

The transition-metal phosphorous trichalcogenides MPX3, where M is a 3d transition metal and X a chalcogen element, are two-dimensional (2D), magnetic van der Waals (vdW) materials, where the interplay between low dimensionality, electronic correlations, spin-orbit coupling, and magnetism leads to interesting and exotic properties, with potential use in novel spin-electronic and spin-optical devices. This interplay is highly sensitive to external pressure in these low-dimensional, layered materials, since the application of pressure causes a reduction of the vdW gap with large effects on the properties. Thus, a plethora of phenomena are induced in the MPX3 compounds by external pressure, including dimensional crossover, insulator-to-metal transition, spin-crossover transition, structural phase transitions, and superconductivity, as reported in the literature. Within this project, we will systematically study the electronic excitations, charge dynamics, and lattice dynamics in 2D magnetic vdW materials MPX3 at ambient conditions, during the pressure-induced insulator-to-metal transition, and in the high-pressure metallic phases. The expected results will provide a unique insight into the interesting pressure-induced phenomena, namely dimensionality crossover from 1D conduction channels to 3D transport without crystal symmetry change, spin-crossover transition, insulator-to-metal transition, structural phase transitions, and high-pressure metallic phases. Our study will also clarify the relevance of electronic correlations in the metallic phases of MPX3 materials at high pressures. As experimental tools we will apply optical spectroscopy over a broad frequency range and inelastic Raman scattering measurements combined with the diamond anvil pressure cell technique and cryogenic cooling.

• DFG Programme: Research Grants