Eur. Phys. J. B (2018) 91: 216
https://doi.org/10.1140/epjb/e2018-90161-2

Regular Article

Benchmarking nonequilibrium Green’s functions against configuration interaction for time-dependent Auger decay processes^★

¹ Max Planck Institute for the Structure and Dynamics of Matter and Center for Free-Electron Laser Science, Luruper Chaussee 149, 22761 Hamburg, Germany
² CNR-ISM, Division of Ultrafast Processes in Materials (FLASHit), Area della ricerca di Roma 1, Monterotondo Scalo, Italy
³ Dipartimento di Fisica, Università di Roma Tor Vergata, Via della Ricerca Scientifica, 00133 Roma, Italy
⁴ Center for Computational Quantum Physics (CCQ), The Flatiron Institute, 162 Fifth avenue, New York, NY 10010, USA
⁵ Nano-Bio Spectroscopy Group, Universidad del País Vasco, 20018 San Sebastián, Spain
⁶ INFN, Sezione di Roma Tor Vergata, Via della Ricerca Scientifica 1, 00133 Roma, Italy

^a e-mail: gianluca.stefanucci@roma2.infn.it

Received: 13 March 2018
Received in final form: 25 June 2018
Published online: 1 October 2018

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–Schlüter equation may provide useful insights for the development of TDDFT exchange-correlation potentials with a history dependence.