Institut für Festkörperphysik, Leibniz Universität Hannover, Hannover, Germany.
J Phys Condens Matter. 2011 Mar 23;23(11):112204. doi: 10.1088/0953-8984/23/11/112204. Epub 2011 Mar 1.
Using monolayer graphene as a model system for a purely two-dimensional (2D) electron gas, we show by energy electron loss spectroscopy, highly resolved both in energy and momentum, that there is a significant probability for the excitation of not only one but two dispersing losses. The appearance of both losses is independent of the substrate (we tested graphene on the Si face of 6H-SiC(0001), and on Ir(111) without and with an intercalated Na layer), and the ratio of the slope in the dispersion curves varies between 1.4 (SiC) and 2. While the lower dispersion curve can be attributed to the excitation of the sheet plasmon, in agreement with theoretical model calculations, the upper dispersion branch has not been identified before for plasmonic excitations in a 2D electron gas, and we assign it tentatively to the excitation of a multipole sheet plasmon.
我们使用单层石墨烯作为纯粹二维（2D）电子气的模型体系，通过能量电子损失谱（energy electron loss spectroscopy）进行了高能量和高动量分辨的测量，结果表明不仅存在一个而是两个分散损耗的激发的显著概率。两个损耗的出现都与衬底无关（我们在 6H-SiC(0001)的 Si 面上的石墨烯，以及在 Ir(111)上的没有和插入 Na 层的石墨烯上进行了测试），而且色散曲线斜率的比值在 1.4（SiC）到 2 之间变化。虽然较低的色散曲线可以归因于片体等离子体的激发，这与理论模型计算一致，但对于 2D 电子气中的等离子体激发，以前尚未识别出上色散分支，我们暂时将其分配给多极片体等离子体的激发。
