Fingerprints of Excitonic Collective Modes in the Two-Dimensional Electron Gas
Abstract
The two-dimensional homogeneous electron gas (2D HEG) is a prototype system of fundamental interest that can be realized experimentally over a wide range of densities. Here, we investigate its collective charge excitations at low densities, using time-dependent density functional theory. We demonstrate that, beyond traditional plasmons, new collective excitonic modes emerge for a Wigner-Seitz radius larger than rs ≈ 1. These excitonic modes leave characteristic fingerprints in experimentally accessible quantities, namely, asymmetric peak structures in the loss function and very strong Friedel-like oscillations in the static linear density response that increase when the system approaches a regime of instability. Indeed, at low enough densities the collective modes cross the zero energy axis, indicating an instability of the paramagnetic 2D HEG towards the formation of a charge-density-wave phase with excitonic origin. These findings provide valuable insights for the experimental detection of excitonic collective modes in tunable 2D electron systems and contribute to the fundamental understanding of many-body effects in low-density electron gases.
Versions
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BibTeX
@misc{wolff2026fingerprints,
title = {{Fingerprints of Excitonic Collective Modes in the Two-Dimensional Electron Gas}},
author = {Jakob Wolff and Silvana Botti and Lucia Reining and Matteo Gatti},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.11138},
eprint = {2609.11138},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.11138},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Fingerprints of Excitonic Collective Modes in the Two-Dimensional Electron Gas
AU - Jakob Wolff
AU - Silvana Botti
AU - Lucia Reining
AU - Matteo Gatti
PY - 2026
DA - 2026/09/10
PB - arXiv
DO - 10.48550/arxiv.2609.11138
UR - https://arxiv.org/abs/2609.11138
AB - The two-dimensional homogeneous electron gas (2D HEG) is a prototype system of fundamental interest that can be realized experimentally over a wide range of densities. Here, we investigate its collective charge excitations at low densities, using time-dependent density functional theory. We demonstrate that, beyond traditional plasmons, new collective excitonic modes emerge for a Wigner-Seitz radius larger than r_s ≈ 1. These excitonic modes leave characteristic fingerprints in experimentally accessible quantities, namely, asymmetric peak structures in the loss function and very strong Friedel-like oscillations in the static linear density response that increase when the system approaches a regime of instability. Indeed, at low enough densities the collective modes cross the zero energy axis, indicating an instability of the paramagnetic 2D HEG towards the formation of a charge-density-wave phase with excitonic origin. These findings provide valuable insights for the experimental detection of excitonic collective modes in tunable 2D electron systems and contribute to the fundamental understanding of many-body effects in low-density electron gases.
ER -