Early-stage dynamics of metallic droplets embedded in the nanotextured Mott insulating phase of V$_2$O$_3$

TL;DR

This study investigates the initial formation and growth of metallic nano-droplets during the insulator-to-metal transition in V$_2$O$_3$, revealing the role of domain boundaries and photo-induced effects in ultrafast switching.

Contribution

It combines X-ray microscopy and ultrafast spectroscopy to uncover the early-stage dynamics of metallic droplet nucleation in V$_2$O$_3$, highlighting the influence of nanotexture and non-thermal pathways.

Findings

Metallic nano-droplets nucleate at insulating domain boundaries.

Photo-induced changes accelerate metallic droplet expansion.

The insulating phase's nanotexture influences transition timescales.

Abstract

Unveiling the physics that governs the intertwining between the nanoscale self-organization and the dynamics of insulator-to-metal transitions (\textit{IMT}) is key for controlling on demand the ultrafast switching in strongly correlated materials and nano-devices. A paradigmatic case is the \textit{IMT} in V$_2$O$_3$, for which the mechanism that leads to the nucleation and growth of metallic nano-droplets out of the supposedly homogeneous Mott insulating phase is still a mystery. Here, we combine X-ray photoemission electron microscopy and ultrafast non-equilibrium optical spectroscopy to investigate the early stage dynamics of isolated metallic nano-droplets across the \textit{IMT} in V$_2$O$_3$ thin films. Our experiments show that the low-temperature monoclinic antiferromagnetic insulating phase is characterized by the spontaneous formation of striped polydomains, with different lattice distortions. The insulating domain boundaries accommodate the birth of metallic nano-droplets, whose non-equilibrium expansion can be triggered by the photo-induced change of the 3$d$-orbital occupation. We address the relation between the spontaneous nanotexture of the Mott insulating phase in V$_2$O$_3$ and the timescale of the metallic seeds growth. We speculate that the photoinduced metallic growth can proceed along a non-thermal pathway in which the monoclinic lattice symmetry of the insulating phase is partially retained.