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arXiv · 2202.11589

Unphysical Discontinuities, Intruder States and Regularization in $GW$ Methods

Enzo Monino·Pierre-François Loos
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Abstract

By recasting the non-linear frequency-dependent $GW$ quasiparticle equation into a linear eigenvalue problem, we explain the appearance of multiple solutions and unphysical discontinuities in various physical quantities computed within the $GW$ approximation. Considering the $GW$ self-energy as an effective Hamiltonian, it is shown that these issues are key signatures of strong correlation in the $(N\pm1)$-electron states and can be directly related to the intruder state problem. A simple and efficient regularization procedure inspired by the similarity renormalization group is proposed to avoid such issues and speed up convergence of partially self-consistent $GW$ calculations.

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Enzo Monino, Pierre-François Loos. 2022-02-23. Unphysical Discontinuities, Intruder States and Regularization in $GW$ Methods. https://doi.org/10.1063/5.0089317

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