二维电子气中激子集体模式的指纹特征

中文摘要 AI 辅助

二维均匀电子气（2D HEG）是一个具有基础研究意义的原型系统，可以在实验上于广泛的密度范围内实现。本文利用含时密度泛函理论，研究了其在低密度下的集体电荷激发。我们证明，除了传统的等离激元之外，当维格纳-赛茨半径大于 $r_{\mathrm s} \approx 1$ 时，会出现新的集体激子模式。这些激子模式在实验可观测的量中留下特征指纹，即损耗函数中的不对称峰结构，以及静态线性密度响应中非常强的类弗里德尔振荡，且当系统接近不稳定区域时，这些振荡会增强。实际上，在足够低的密度下，集体模式穿越零能量轴，表明顺磁二维电子气向具有激子起源的电荷密度波相的不稳定性转变。这些发现为在可调谐二维电子系统中实验探测激子集体模式提供了有价值的见解，并有助于对低密度电子气中多体效应的基本理解。

英文摘要

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 $r_{\mathrm s} \approx 1$. 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.

发表机构

• Friedrich-Schiller-Universät Jena（耶拿弗里德里希·席勒大学）
• Ruhr University Bochum（波鸿鲁尔大学）
• École Polytechnique, Institut Polytechnique de Paris（巴黎综合理工学院，巴黎理工学院）
• Synchrotron SOLEIL（SOLEIL同步辐射中心）

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