Dynamical singlets and correlation-assisted Peierls transition in VO2

TL;DR

This paper presents a theoretical study of the metal-insulator transition in VO2, highlighting the role of dynamical V-V singlet pairs and correlation effects in driving the Peierls transition.

Contribution

It introduces a combined cluster dynamical mean field and density functional approach to explain the transition mechanism in VO2.

Findings

VO2 forms dynamical V-V singlet pairs due to strong correlations.

The transition involves a correlation-assisted Peierls gap opening.

VO2 is not a conventional Mott insulator.

Abstract

A theory of the metal-insulator transition in vanadium dioxide from the high-temperature rutile to the low- temperature monoclinic phase is proposed on the basis of cluster dynamical mean field theory, in conjunction with the density functional scheme. The interplay of strong electronic Coulomb interactions and structural distortions, in particular the dimerization of vanadium atoms in the low temperature phase, plays a crucial role. We find that VO2 is not a conventional Mott insulator, but that the formation of dynamical V-V singlet pairs due to strong Coulomb correlations is necessary to trigger the opening of a Peierls gap.