Center for Computational Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki, Japan.
Graduate School of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki, Japan.
J Chem Phys. 2019 Mar 7;150(9):094101. doi: 10.1063/1.5068711.
We propose a theoretical and computational approach to investigate temporal behavior of a nonlinear polarization in a 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 in 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.
我们提出了一种理论和计算方法，用于研究在强超短脉冲电场作用下的非线性极化的时间行为。采用第一性原理含时密度泛函理论来描述电子动力学。通过对具有相同时间分布但不同幅度的脉冲电场诱导的电子动力学进行几次计算，提取出三阶非线性极化的时间演化。我们讨论了非线性极化演化的特征以及通过拟合极化来提取非线性灵敏度和时间延迟。我们还对电子密度随时间和空间的变化进行了场幅度的级数展开分解。这有助于深入了解原子尺度上非线性极化的起源。
