Amphi Charpak, tour 22, R-d-C
Matteo Calandra – Université de Trento
In this talk, I will introduce a theoretical approach to ultrafast phase transitions able to capture both the electron and phonon dynamics after laser pumping on a time scale ranging from a few femtoseconds to several picoseconds after laser irradiation.
At short times, the method relies on the solution of the Bloch equations coupled to the Ehrenfest dynamics. It includes the electric field of the pump as well as the electron-phonon, electron-electron, and phonon-phonon scattering completely from first principles.
At longer times, before electron-hole recombination, when the electron-electron interaction generates a photoexcited quasi-equilibrium electron-hole plasma, the approach is based on a constrained density functional perturbation theory (cDFPT) scheme accounting both for the presence of holes in the valence band and electrons in the conduction band (two Fermi levels approach). In this framework, calculation of forces, phonon dispersion, and electron-phonon coupling are possible, as well as molecular dynamics with machine learning potential in the presence of an electron-hole plasma.
I will showcase the application of the method to several materials and phenomena, including low-dimensional dichalcogenides, ferroelectrics, thermoelectrics and non-thermal melting of solids.
This work is funded by the European Union (ERC, DELIGHT, 101052708)
References:
[1] G. Marini and M. Calandra, Lattice dynamics of photoexcited insulators from constrained density-functional perturbation theory, PRB 104, 144103 (2021)
[2] K. Holtgrewe, G. Marini and M. Calandra, Light-Induced Polaronic Crystals in Single-Layer Transition Metal Dichalcogenides, Nano Letters 24 (42), 13179-13184 (2024)
[3] M Furci, G Marini, M Calandra, First-Order Rhombohedral-to-Cubic Phase Transition in Photoexcited GeTe, Physical Review Letters 132 (23), 236101 (2024)
[4] S Mocatti, G Marini, M Calandra, Light-Induced Nonthermal Phase Transition to the Topological Crystalline Insulator State in SnSe,
The Journal of Physical Chemistry Letters 14 (41), 9329-9334
[5] M. Huber et al. ,Ultrafast creation of a light-induced semimetallic state in strongly excited 1T-TiSe2, Science Advances 10 (19), eadl4481 (2024)
[6] A. Corradini, G. Marini and M. Calandra, A machine learning approach to light-induced order-disorder phase transitions: large-scale long-time simulations with ab initio accuracy, submitted.
