Metal-insulator Transition in VO2: a DFT+DMFT perspective

TL;DR

This paper uses a combined DFT+DMFT approach to study the electronic structure of VO$_2$'s metallic and insulating phases, revealing a Mott-driven transition with temperature-dependent gaps and complex intersite correlations.

Contribution

It introduces a fully self-consistent DFT+DMFT method to elucidate the Mott physics and gap mechanisms in VO$_2$, highlighting the role of intersite correlations and temperature effects.

Findings

Mott physics is crucial in all VO$_2$ phases.

The transition involves local moment formation and intersite correlations.

The insulating gap is temperature-dependent and collapses with increased electronic temperature.

Abstract

We present a theoretical investigation of the electronic structure of rutile (metallic) and M$_1$ and M$_2$ monoclinic (insulating) phases of VO$_2$ employing a fully self-consistent combination of density functional theory and embedded dynamical mean field theory calculations. We describe the electronic structure of the metallic and both insulating phases of VO$_2$, and propose a distinct mechanism for the gap opening. We show that Mott physics plays an essential role in all phases of VO$_2$: undimerized vanadium atoms undergo classical Mott transition through local moment formation (in the M$_2$ phase), while strong superexchange within V-dimers adds significant dynamic intersite correlations, which remove the singularity of self-energy for dimerized V-atoms. The resulting transition from rutile to dimerized M$_1$ phase is adiabatically connected to Peierls-like transition, but is better characterized as the Mott transition in the presence of strong intersite exchange. As a consequence of Mott physics, the gap in the dimerized M$_1$ phase is temperature dependent. The sole increase of electronic temperature collapses the gap, reminiscent of recent experiments.