Nonlinear polarization evolution using time-dependent density functional theory

TL;DR

This paper introduces a first-principles computational method using time-dependent density functional theory to analyze the ultrafast nonlinear polarization response of materials to intense electric fields, revealing atomic-scale insights.

Contribution

It develops a novel approach combining TDDFT simulations with polarization analysis to study nonlinear optical responses at the atomic level.

Findings

Characterized the temporal evolution of third-order nonlinear polarization.

Extracted nonlinear susceptibilities and time delays from simulations.

Decomposed electron density changes to understand nonlinear polarization origins.

Abstract

We propose a theoretical and computational approach to investigate temporal behavior of a nonlinear polarization in perturbative regime induced by an intense and ultrashort pulsed electric field. First-principles time-dependent density functional theory is employed to describe the electron dynamics. Temporal evolution of third-order nonlinear polarization is extracted from a few calculations of electron dynamics induced by pulsed electric fields with the same time profile but different amplitudes. We discuss characteristic features of the nonlinear polarization evolution as well as an extraction of nonlinear susceptibilities and time delays by fitting the polarization. We also carry out a decomposition of temporal and spatial changes of the electron density in power series with respect to the field amplitude. It helps to get insight into the origin of the nonlinear polarization in atomic scale.