April 16 2019

Seminar
Sala Riunioni -  Time: 15.30
Università Cattolica del Sacro Cuore, Via Musei 41, Brescia (Italy)

Flier

Introduce:
PhD student Laura BIGNOTTI
Università Cattolica del Sacro Cuore

Speaker:
PhD student Andrea RONCHI
KU Leuven

Abstract
Unveiling the physics that governs the intertwining between the nanoscale self-organization and the dynamics of insulator-to-metal transitions (IMT) is key for controlling on demand the ultrafast switching in strongly correlated materials and nano-devices. A paradigmatic case is the IMT in V₂O₃, 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 IMT in V₂O₃ thin films. Our experiments show that the low-temperature monoclinic antiferromagnetic insulating phase is characterized by the spontaneous formation of striped polydomains, which are intrinsic to martensitic transformations. 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 3d-orbital occupation. We address the relation between the spontaneous nanotexture of the Mott insulating phase in V2O3 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.