Ultrafast phonon dynamics in two-dimensional and layered materials.

Recent advancements in pump-probe spectroscopy and scattering techniques have unlocked unprecedented capabilities to directly probe phonons, electron-phonon interactions, and their non-equilibrium dynamics. Achieving a theoretical description of these phenomena from first principles is of paramount importance for understanding and harnessing the emergent behaviour of light-driven solids.

In this talk, I will discuss the recent progress and open challenges in the theoretical description of the ultrafast phonon dynamics based on ab-initio electronic-structure approaches. Particular emphasis will be placed on the problems of (i) lattice thermalization in photoexcited semiconductors, and (ii) coherent lattice dynamics in semimetals. In both cases, the systematic and seamless modeling of electron-phonon and phonon-phonon interactions stands as an essential prerequisite for the attainment of realistic insights into pump-probe experiments. I will exemplify these concepts within the context of 2D and layered materials, where ultrafast diffuse scattering measurements have recently enabled to directly probe of the non-equilibrium phonon dynamics.