Nonlinear polarization evolution using time-dependent density functional theory.

Area of Science:

• Quantum mechanics
• Computational physics
• Materials science

Background:

• Understanding electron dynamics is crucial for designing new materials.
• Nonlinear optical phenomena are key to advanced technologies.
• Pulsed electric fields induce complex electronic responses.

Purpose of the Study:

• To develop a theoretical and computational framework for investigating nonlinear polarization.
• To analyze the temporal behavior of electron dynamics under intense ultrashort pulsed electric fields.
• To extract nonlinear susceptibilities and time delays from simulations.

Main Methods:

• Utilizing first-principles time-dependent density functional theory (TD-DFT).
• Performing calculations with pulsed electric fields of varying amplitudes.
• Analyzing electron dynamics and nonlinear polarization evolution.
• Decomposing electron density changes into power series.

Main Results:

• Successfully extracted temporal evolution of third-order nonlinear polarization.
• Identified characteristic features of nonlinear polarization.
• Determined nonlinear susceptibilities and time delays through fitting.
• Gained atomic-scale insights into the origins of nonlinear polarization.

Conclusions:

• The proposed method effectively captures nonlinear polarization dynamics.
• TD-DFT provides a robust tool for studying electron responses to pulsed fields.
• The findings offer a deeper understanding of light-matter interactions at the atomic level.