VO2 under hydrostatic pressure: Isostructural phase transition close to a critical endpoint

The authors unveil here new findings in the realm of phase transitions in VO${}₂$ single crystals, all achieved under hydrostatic pressure conditions. They provide experimental results, exploiting the observation of soft phonons through Raman spectroscopy and high-quality structural refinements. These findings offer a fresh perspective on phase diagrams, including a precise description of the M${}₁$-M${}₁^{\ensuremath{'}}$ isostructural transition occurring at a staggering 14 GPa. The study also reveals that isothermal compression at 298 K drives a thrilling journey close to the critical point. The authors present the first Raman signature of the elusive metallic $X$-phase, observed at pressures exceeding 32 GPa.