The pressure-induced metallization of monoclinic vanadium dioxide

Abstract

In this study, the high-pressure behavior of monoclinic vanadium dioxide (VO₂ (M₁)) was revisited using infrared reflectivity (IR) spectroscopy, Raman spectroscopy and in situ synchrotron X-ray diffraction (XRD) up to 64.7 GPa. Upon compression, VO₂ (M₁) follows the expected the structure transition sequence, M₁ → M′₁ → X, and we found that the structural transition from M′₁ to X phase is completed at about 59 GPa. Moreover, our IR data demonstrated that the M′₁ phase is a semiconductor within the pressure region of 11.4–43.2 GPa and became metallic with further compression, and that the X phase is metallic. Further analysis suggests that the pressure-induced metallization (PIM) of the M′₁ phase is associated with electron–electron correlations, while the PIM from the M′₁ to the X phases is relate to structural phase transitions. These results provide further insight into the PIM of VO₂ (M₁).