Dresden 2026 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 27: 2D Materials: Electronic structure, excitations, etc. II (joint session O/HL/TT)
HL 27.6: Vortrag
Mittwoch, 11. März 2026, 11:45–12:00, TRE/MATH
Fingerprints of Excitonic Collective Modes in the Two-Dimensional Electron Gas — •Jakob Wolff1,2,3, Silvana Botti2,3, Lucia Reining4,3, and Matteo Gatti4,3,5 — 1Institut für Festkörpertheorie- und Optik, Friedrich-Schiller-Universität Jena, Germany — 2Research Center Future Energy Materials and Systems, University Alliance Ruhr and Interdisciplinary Centre for Advanced Materials Simulation, Faculty of Physics and Astronomy, Ruhr University Bochum, Germany — 3European Theoretical Spectroscopy Facility (ETSF) — 4LSI, CNRS, CEA/DRF/IRAMIS, École polytechnique, Institut Polytechnique de Paris, France — 5Synchrotron SOLEIL, Gif-sur-Yvette, France
We investigate the collective charge excitations of the two-dimensional homogeneous electron gas in the low density regime within the framework of time-dependent density functional theory. We show that beyond the well-known plasmons new collective excitonic modes emerge, which leave characteristic fingerprints in experimentally accessible quantities, such as asymmetric peak structures in the loss function and enhanced Friedel oscillations. Further, at sufficiently low densities the collective modes become imaginary, indicating an instability towards the formation of a charge-density-wave phase with excitonic origin.
Keywords: two-dimensional homogeneous electron gas; time-dependent density functional theory; excitonic collective modes; theoretical spectroscopy; linear response