Exploration de l'effet de la pression et la dimensionnalité sur la dynamique ultra-rapide de matériaux quantiques

Correlated quantum materials exhibit complex phase transitions where electronic and structural degrees of freedom strongly interact. Ultrafast optical excitation provides access to these fundamental dynamics and offers new pathways for control. This thesis investigates two main aspects: the role of pressure and the role of dimensionality. In V₂O₃, a prototype Mott insulator, pump–probe experiments under pressure reveal the generation of coherent phonons whose frequency and lifetime evolve markedly across the metal–insulator transition. These structural oscillations act as sensitive tracers of the electronic state and highlight the importance of electron– lattice coupling. In a second axis, heterostructures combining carbon nanotubes (CNT) and boron nitride nanotubes (BNNT) were studied by ultrafast spectroscopy and femtosecond electron diffraction. The results demonstrate an ultrafast interlayer charge transfer followed by structural relaxation characterized by inter-tube expansion, revealing the key role of dimensionality and electron–phonon coupling. Finally, exploratory work on EDO-TTF, an organic system with complex structural transitions, complements the study and opens perspectives on the diversity of correlated materials accessible with these approaches. Altogether, these results demonstrate that combining pressure, dimensional confinement, and ultrafast probes is an effective route to understand and control out-of-equilibrium dynamics in correlated materials.