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arXiv · 1611.07456

Helium atom excitations by the GW and Bethe-Salpeter many-body formalism

Jing Li·Markus Holzmann·Ivan Duchemin·Xavier Blase·Valerio Olevano
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Abstract

Helium atom is the simplest many-body electronic system provided by nature. The exact solution to the Schrödinger equation is known for helium ground and excited states, and represents a workbench for any many-body methodology. Here, we check the ab initio many-body GW approximation and Bethe-Salpeter equation (BSE) against the exact solution for helium. Starting from Hartree-Fock, we show that GW and BSE yield impressively accurate results on excitation energies and oscillator strength, systematically improving time-dependent Hartree-Fock. These findings suggest that the accuracy of BSE and GW approximations is not significantly limited by self-interaction and self-screening problems even in this few electron limit. We further discuss our results in comparison to those obtained by time-dependent density-functional theory.

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Jing Li, Markus Holzmann, Ivan Duchemin, Xavier Blase, Valerio Olevano. 2017-03-21. Helium atom excitations by the GW and Bethe-Salpeter many-body formalism. https://doi.org/10.1103/physrevlett.118.163001

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