Theoretical understanding of ultrafast dynamics in hot carrier-lattice interactions

Saranya, Ramesh V. (2022) Theoretical understanding of ultrafast dynamics in hot carrier-lattice interactions. Masters thesis, Indian institute of science education and Research Kolkata.

Text (MS dissertation of Saranya Ramesh V. (17MS157)) 17MS157_Thesis_file.pdf - Submitted Version Restricted to Repository staff only Download (1MB)

Abstract

Irradiation of metals with ultrashort laser pulse can lead to out of equilibrium state of electrons on a femtosecond timescale. Theoretical and experimental studies of the nonequilibrium dynamics of electrons is crucial in providing important information about the ultrafast processes of both metals and semiconductors. Here in this work, thermalization of electrons is investigated numerically by considering Boltzmann transport formalism and taking the relevant scattering mechanisms such as electron-electron (e-e), electron-phonon (e-ph), phonon-electron (ph-e), and phonon-phonon (ph-ph) into account. We have done numerical modeling to study the relaxation dynamics in aluminium by taking non-equilibrium electron and quasi-equilibrium phonon distributions. The energy absorbed by electrons is further transferred to longitudinal acoustic (LA) and transverse acoustic (TA) phononic subsystems. Subsequently, these subsystems exchange energy between them, resulting in the equilibration of the entire system. We have studied the influence of laser pulse parameters on the relaxation dynamics of aluminum. To investigate the role of material parameters on relaxation dynamics, we apply our model to three other metals (copper, silver and gold) and compared them with aluminium. Our study validates the dependency of thermalization time and electron-phonon coupling strength on the excitation type and material properties.

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