Probing the electronic and local structural changes across the pressure-induced insulator-to-metal transition in VO 2

Local and electronic structures of vanadium in are studied across the high-pressure insulator-to-metal (IMT) transition using V K -edge x-ray absorption spectroscopy. Unlike the temperature-induced IMT, pressure-induced metallization leads to only subtle changes in the V K -edge prepeak structure, indicating a different mechanism involving smaller electronic spectral weight transfer close to the chemical potential. Intriguingly, upon application of the hydrostatic pressure, the electronic structure begins to show substantial changes well before the occurrence of the IMT and the associated structural transition to an anisotropic compression of the monoclinic metallic phase.