Benchmarking Nonequilibrium Green's Functions against Configuration Interaction for time-dependent Auger decay processes

TL;DR

This paper evaluates a Nonequilibrium Green's Function approach for modeling Auger decay in photoionized molecules, comparing its accuracy to Configuration Interaction calculations in model systems, and discusses implications for time-dependent density functional theory.

Contribution

It introduces and benchmarks a NEGF method for Auger decay processes, highlighting the importance of electron-electron correlations and memory effects for accuracy.

Findings

NEGF captures key relaxation dynamics when Auger electron energy is high.

Dynamical correlations and memory effects are crucial for accurate results.

The approach offers insights for developing improved TDDFT exchange-correlation potentials.

Abstract

We have recently proposed a Nonequilibrium Green's Function (NEGF) approach to include Auger decay processes in the ultrafast charge dynamics of photoionized molecules. Within the so called Generalized Kadanoff-Baym Ansatz the fundamental unknowns of the NEGF equations are the reduced one-particle density matrix of bound electrons and the occupations of the continuum states. Both unknowns are one-time functions like the density in Time-Dependent Functional Theory (TDDFT). In this work we assess the accuracy of the approach against Configuration Interaction (CI) calculations in one-dimensional model systems. Our results show that NEGF correctly captures qualitative and quantitative features of the relaxation dynamics provided that the energy of the Auger electron is much larger than the Coulomb repulsion between two holes in the valence shells. For the accuracy of the results dynamical electron-electron correlations or, equivalently, memory effects play a pivotal role. The combination of our NEGF approach with the Sham-Schl\"uter equation may provide useful insights for the development of TDDFT exchange-correlation potentials with a history dependence.