Nonlinear response in the cumulant expansion for core-level photoemission

Marilena Tzavala (1, 2, 3) , J. Kas (1, 3) , Lucia Reining (2, 3) , J. Rehr (1, 3)

1 Department of Physics [Washington]
2 LSI - Laboratoire des Solides Irradiés - Irradiated Solids Laboratory
3 ETSF - European Theoretical Spectroscopy Facility

Most currently used approximations for the one-particle Green's function G in the framework of many-body perturbation theory, such as Hedin's GW approximation or the cumulant GW+C approach, are based on a linear-response approximation for the screened interaction W. The extent to which such a hypothesis is valid and ways to go beyond have been explored only very little. Here we show how to derive a cumulant Green's function beyond linear response from the equation of motion of the Green's function in a functional derivative formulation. The results can be written in a compact form, which opens the possibility to calculate the corrections in a first-principles framework using time-dependent density functional theory. In order to illustrate the potential importance of the corrections, numerical results are presented for a model system with a core level and two valence orbitals.

Domaines: Autre [cond-mat.other]

Marilena Tzavala, J. Kas, Lucia Reining, J. Rehr. Nonlinear response in the cumulant expansion for core-level photoemission. Physical Review Research, 2020, 2 (3), ⟨10.1103/PhysRevResearch.2.033147⟩. ⟨hal-03098580⟩