Electronic and vibrational properties of the two-dimensional Mott insulator V0.9PS3 under pressure

We present a Raman spectroscopic study of the layered antiferromagnetic Mott insulator V(0.9)PS(3 )and demonstrate the evolution of the spectra with applied quasihydrostatic pressure. Clear features in the spectra are seen at the pressures identified as corresponding to a structural transition between 20 and 80 kbar and the insulator-metal transition at 120 kbar. The feature at 120 kbar can be understood as a stiffening of interplanar vibrations, linking the metallization to a crossover from two- to three-dimensionality. Theoretical ab initio calculations, using the previously determined high-pressure structures, were able to reproduce the measured spectra and map each peak to specific vibration modes. We additionally show calculations of the high-pressure band structure in these materials, where the opening of a band gap with an included Hubbard U term and its subsequent closing with pressure are clearly demonstrated. This little-studied material shows great promise as a model system for the fundamental study of low-dimensional magnetism and Mott physics.