# Regensburg 2019 – wissenschaftliches Programm

## Bereiche | Tage | Auswahl | Suche | Aktualisierungen | Downloads | Hilfe

# DS: Fachverband Dünne Schichten

## DS 6: Frontiers of Electronic-Structure Theory: Focus on the Interface Challenge II (joint session O/CPP/DS/TT)

### DS 6.4: Vortrag

### Montag, 1. April 2019, 15:45–16:00, H9

**Dielectric function of homogeneous electron gas from Bethe-Salpeter equation** — •Jaakko Koskelo^{1,2}, Martin Panholzer^{2,3}, Lucia Reining^{1,2}, and Matteo Gatti^{1,2,4} — ^{1}Laboratoire des Solides Irradiés, École Polytechnique, CNRS, CEA, Université Paris-Saclay, F-91128 Palaiseau, France — ^{2}ETSF — ^{3}Institute for Theoretical Physics, Johannes Kepler University, Linz, Austria — ^{4}Synchrotron SOLEIL, France

The homogeneous electron gas (HEG) is one of the most important model systems in condensed matter physics, and it has been subject of a great number of studies. Some properties of HEG such as total energy and static correlation functions can be obtained from quantum Monte Carlo simulations with great accuracy, but for dynamical correlation functions only very few results are available.

Methods based on the Bethe-Salpeter equation (BSE) have been very succesful in semiconductors and insulators, but metals have been less studied. In this contribution, we use the BSE in its standard approximations, including a statically screened electron-hole interaction, to study the dielectric function of HEG. We find significant differences in static screening and spectra compared to other approaches. In particular, the BSE in its current approximations fails to reproduce the negative static screening in the low-density HEG, which is related to a so-called ghost exciton. We also use the time-dependent mean-density approximation [1] in order to compare our results to experimental loss spectra of sodium.

[1] M. Panholzer et al, Phys. Rev. Lett. **120**, 166402 (2018).