An Ab Initio Description of the Mott Metal-Insulator Transition of M$_{2}$ Vanadium Dioxide

TL;DR

This paper presents an  approach using GW approximation to analyze the Mott metal-insulator transition in M vanadium dioxide, revealing the interplay of structural distortions and electronic correlations.

Contribution

It demonstrates that modified GW calculations can accurately describe atomic and electronic structure interactions in Mott transitions.

Findings

Peierls pairing causes bonding-antibonding splitting in M VO.

Antiferroelectric distortion reduces electronic repulsion.

Bonding states are lowered into the Hubbard band, antibonding states into the upper Hubbard band.

Abstract

Using an \textit{ab initio} approach based on the GW approximation which includes strong local \textbf{k}-space correlations, the Metal-Insulator Transition of M$_2$ vanadium dioxide is broken down into its component parts and investigated. Similarly to the M$_{1}$ structure, the Peierls pairing of the M$_{2}$ structure results in bonding-antibonding splitting which stabilizes states in which the majority of the charge density resides on the Peierls chain. This is insufficient to drop all of the bonding states into the lower Hubbard band however. An antiferroelectric distortion on the neighboring vanadium chain is required to reduce the repulsion felt by the Peierls bonding states by increasing the distances between the vanadium and apical oxygen atoms, lowering the potential overlap thus reducing the charge density accumulation and thereby the electronic repulsion. The antibonding states are simultaneously pushed into the upper Hubbard band. The data indicate that sufficiently modified GW calculations are able to describe the interplay of the atomic and electronic structures occurring in Mott metal-insulator transitions.