Time-dependent second Born calculations for model atoms and molecules in strong laser fields

TL;DR

This paper extends nonequilibrium Green's function methods to study the response of atoms and molecules in strong laser fields, demonstrating the importance of electron-electron correlations and providing scalable computational techniques.

Contribution

It introduces a time-dependent second Born approach for NEGF calculations on atoms and molecules in intense laser fields, improving correlation effects modeling.

Findings

Second Born approximation captures electron-electron correlations effectively.

Comparison shows improved accuracy over time-dependent Hartree-Fock.

Develops scalable parallel algorithms for NEGF computations.

Abstract

Using the finite-element discrete variable representation of the nonequilibrium Green's function (NEGF) we extend previous work [K.~Balzer et al., Phys. Rev. A \textbf{81}, 022510 (2010)] to nonequilibrium situations and compute---from the two-time Schwinger-Keldysh-Kadanoff-Baym equations---the response of the helium atom and the heteronuclear molecule lithium hydride to laser fields in the uv and xuv regime. In particular, by comparing the one-electron density and the dipole moment to time-dependent Hartree-Fock results on one hand and the full solution of the time-dependent Schr\"odinger equation on the other hand, we demonstrate that the time-dependent second Born approximation carries valuable information about electron-electron correlation effects. Also, we outline an efficient distributed memory concept which enables a parallel and well scalable algorithm for computing the NEGF in the two-time domain.