Evidence of a pressure-induced metallization process in monoclinic VO$_2$

TL;DR

This study investigates how high pressure induces a transition from insulating to metallic behavior in monoclinic VO₂, revealing a new metallic phase at room temperature under pressure.

Contribution

It provides experimental evidence of pressure-induced metallization in monoclinic VO₂ and identifies a new metallic phase accessible at room temperature under high pressure.

Findings

Stable lattice dynamics up to ~10 GPa

Onset of metallization via band gap filling above P*

Discovery of a room temperature metallic phase in monoclinic VO₂

Abstract

Raman and combined trasmission and reflectivity mid infrared measurements have been carried out on monoclinic VO$_2$ at room temperature over the 0-19 GPa and 0-14 GPa pressure ranges, respectively. The pressure dependence obtained for both lattice dynamics and optical gap shows a remarkable stability of the system up to P*$\sim$10 GPa. Evidence of subtle modifications of V ion arrangements within the monoclinic lattice together with the onset of a metallization process via band gap filling are observed for P$>$P*. Differently from ambient pressure, where the VO$_2$ metal phase is found only in conjunction with the rutile structure above 340 K, a new room temperature metallic phase coupled to a monoclinic structure appears accessible in the high pressure regime, thus opening to new important queries on the physics of VO$_2$.