Spatially non-homogeneous metallization of VO2: a TDDFT+DMFT analysis

TL;DR

This study uses advanced ab initio methods to analyze the ultrafast spatial breakdown of insulating VO2, revealing preferential metallization along vanadium chains and complex charge dynamics involving oxygen atoms, aligning with experimental observations.

Contribution

It introduces a combined TDDFT+DMFT approach to elucidate atomistic mechanisms of ultrafast phase transition in VO2, highlighting spatially non-homogeneous metallization patterns.

Findings

Initial metallization occurs along vanadium dimer chains.

Growth of CR-elongated metallic bubbles observed.

Charge transfer involves oxygen atoms and affects lattice structure.

Abstract

We provide insights into the atomistic details of the ultrafast spatially-resolved breakdown of the insulating M1 phase in bulk VO2 employing an ab initio technique based on time-dependent density-functional theory and dynamical mean-field theory (DMFT-TDDFT). We find that the system is initially metallized preferentially along the vanadium-dimer chains (CR axis), with a subsequent growth of CR-elongated metallic bubbles. Moreover, we trace the breakdown of the insulating phase to two types of oxygen atoms, resulting from vanadium dimerization, which produce an unusual charge-density modulation in the oxygen-atom chains with significant charge transfer to the inter-dimer distance. These results are in qualitative agreement with experimental data and shed light on the interplay between valence charge and lattice structure and its role in the ultrafast response of strongly correlated insulators.