Crystal response in the presence of femtosecond-laserinduced electron dynamics

• Applicant: Dr. Tobias Zier
• Subject Area: Theoretical Condensed Matter Physics
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 465615881

Intense femtosecond-laser pulses interact in the first place with the electronic system of the excited solid system. By the excitation a non-equilibrium electronic distribution is induced. The main objective of this proposed work is to analyze theoretically the impact of that laser-induced electronic non-equilibrium distribution and the ensuing ultrafast electron dynamics arising from the highly excited electronic system to structural dynamics after a femtosecond-laser excitation. In particular, we plan to develop a theoretical framework that is able to simulate crystal dynamics consistently in the presence of a non-equilibrium distribution of the electrons during and shortly after the femtosecond-laser pulse excitation as well as during the following equilibration process towards a common electronic temperature. Moreover, it should be capable to simulate the dynamics of a solid system with a thermalized electronic system sharing a common temperature. In order to test the performance of the developed code, we plan to introduce development check points at critical stages where our code can be compared to existing theoretical results from existing computations and/or experimental observations. With this we will guarantee and verify the validity of our code. Furthermore, we plan to investigate femtoscond-laser excited silicon dioxide as a test system and first application for our developed code. Accessible time-dependent experiments on nonthermal melting of silicon dioxide at the Stanford Linear Accelerator Center (SLAC), performed by Dr. Félicie Albert, will be used to test and verify our proposed theoretical approach. Moreover, it could also provide important theoretical support to that findings. In more detail, we will address the following questions: How does the electronic non-equilibrium influence the structural response at later times after the excitation? Does the impact vary with the laser intensity? Are the atomic pathways affected by the thermalization process? Do additional forces coming from the non-equilibrium in the beginning lead to new structural phenomena? In a long term perspective we will investigate the applicability of our developed method to attosecond-laser excited solids.

• DFG Programme: WBP Fellowship
• International Connection: USA
• Host: Professor Dr. David Strubbe