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HL: Fachverband Halbleiterphysik

HL 46: Ultra-fast Phenomena II

HL 46.7: Vortrag

Donnerstag, 12. März 2026, 17:00–17:15, POT/0051

Theoretical Modeling of Ultrafast Phase Transitions from the Femtosecond to the Picosecond Scale — Stefano Mocatti, Giovanni Marini, Pierluigi Cudazzo, and •Matteo Calandra — Department of Physics, University of Trento, Via Sommarive 14, 38123 Povo, Italy

In this talk, I will introduce a theoretical approach to ultrafast phase transitions that captures both electron/hole and phonon dynamics following laser pumping, on time scales ranging from a few femtoseconds to several picoseconds after irradiation.

At short times, the method relies on solving the Bloch equations coupled to Ehrenfest dynamics. It includes the electric field of the pump explicitly, as well as carrier-carrier, carrier-phonon, and phonon-phonon scattering, treated entirely from first principles.

At longer times before recombination, when carrier-carrier interactions generate a photoexcited quasi-equilibrium electron-hole plasma, the approach is based on a constrained density-functional perturbation theory (cDFPT) scheme that accounts for the presence of holes in the valence band and electrons in the conduction band (two-Fermi-level approach). In this framework, the calculation of forces, phonon dispersion, and carrier-phonon coupling becomes possible, as well as molecular dynamics with machine-learning potentials in the presence of an electron-hole plasma.

I will showcase applications of the method to several materials.

This work is funded by the European Union (ERC, DELIGHT, 101052708).

Keywords: Modeling of ultrafast phenomena; Non-thermal melting; Ultrafastt Carrier dynamics; Light induced phase transitions