Max Planck Institute for Solid State Research, Heisenbergstrasse 1, D-70569 Stuttgart, Germany.
Nano Lett. 2011 Mar 9;11(3):1379-82. doi: 10.1021/nl200040q. Epub 2011 Feb 15.
We investigate the role of electron-hole correlations in the absorption of free-standing monolayer and bilayer graphene using optical transmission spectroscopy from 1.5 to 5.5 eV. Line shape analysis demonstrates that the ultraviolet region is dominated by an asymmetric Fano resonance. We attribute this to an excitonic resonance that forms near the van Hove singularity at the saddle point of the band structure and couples to the Dirac continuum. The Fano model quantitatively describes the experimental data all the way down to the infrared. In contrast, the common noninteracting particle picture cannot describe our data. These results suggest a profound connection between the absorption properties and the topology of the graphene band structure.
我们使用 1.5 到 5.5eV 的光传输光谱研究了自由-standing 单层和双层石墨烯吸收中电子空穴相关性的作用。线形分析表明，紫外区域主要由不对称的 Fano 共振决定。我们将其归因于在能带结构鞍点处的范霍夫奇点附近形成的激子共振，该共振与狄拉克连续体耦合。Fano 模型定量描述了实验数据，直至红外区域。相比之下，常见的非相互作用粒子图像无法描述我们的数据。这些结果表明了石墨烯能带结构的拓扑与吸收性质之间存在深刻的联系。
