Femtosecond transient absorption spectroscopy to reveal the ultrafast dynamics in solids

Abstract

The investigation of ultrafast dynamics in condensed-phase materials holds significant importance for understanding fundamental physical processes and developing advanced technologies. Our research is mainly divided into two main parts: the development of numerical simulations based on the semiconductor Bloch equations to model the ultrafast light-matter interactions, and the design and implementation of Transient Absorption Spectroscopy system which is a powerful technique to reveal the ultrafast dynamics in solids.

In the first part, the research focuses on the simulation of light-matter interactions using the Semiconductor Bloch Equations (SBE). These equations, which describe the dynamics of electrons in a crystalline solid, are modified and adapted to include the interaction with an external electric field. The simulations provide valuable insights into the ultrafast processes in the crystalline material upon laser excitation. In addition, compared to the well-known Time-Dependent Schrödinger Equation (TDSE) and real-time Time-Dependent Density Functional Theory (rt-TDDFT), this method significantly reduces time and computational resources.

The second part of the research involves the development of a comprehensive transient absorption system setup and measurement methodology. The design and optimization of the experimental apparatus are discussed in detail as well as the data analysis method.

Finally, I performed the Transient Absorption measurements to the Molecular-Beam Epitaxy (MBE) grown monolayer WSe2, and used multiple data analysis methods to extract the dynamics from the data.