Large epitaxial bi-axial strain induces a Mott-like phase transition in VO2

TL;DR

This study demonstrates that large epitaxial biaxial strain can induce a Mott-like electronic phase transition in VO2 without structural change, significantly raising the transition temperature and challenging the traditional Peierls-driven view.

Contribution

It reveals that strain can drive a purely electronic metal-insulator transition in VO2, decoupling it from structural Peierls distortion, and reports a record-high transition temperature.

Findings

Highly strained VO2 remains rutile in both phases.

Electronic transition occurs without Peierls distortion.

Transition temperature reaches ~433 K under large tensile strain.

Abstract

The metal insulator transition (MIT) in VO2 has been an important topic for recent years. It has been generally agreed that the mechanism of the MIT in bulk VO2 is considered to be a collaborative Mott-Peierls transition, however the effect of the strain on the phase transition is much more complicated. In this study the effect of the large strain on the properties of VO2 films was investigated. One remarkable result is that highly strained epitaxial VO2 thin films were rutile in the insulating state as well as in the metallic state. These highly strained VO2 films underwent an electronic phase transition without the concomitant Peierls transition. Our results also show that a very large tensile strain along the c-axis of rutile VO2 resulted in a phase transition temperature of ~ 433 K, much higher than in any previous report. Our findings elicit that the metal insulator transition in VO2 can be driven by an electronic transition alone, rather the typical coupled electronic-structural transition.