Moos G, Gahl C, Fasel R, Wolf M, Hertel T
Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany.
Phys Rev Lett. 2001 Dec 24;87(26):267402. doi: 10.1103/PhysRevLett.87.267402. Epub 2001 Dec 6.
Femtosecond time-resolved photoemission of photoexcited electrons in highly oriented pyrolytic graphite (HOPG) provides strong evidence for anisotropies of quasiparticle (QP) lifetimes. Indicative of such anisotropies is a pronounced anomaly in the energy dependence of QP lifetimes between 1.1 and 1.5 eV--the vicinity of a saddle point in the graphite band structure. This is supported by recent ab initio calculations and a comparison with experiments on defect-enriched HOPG which reveal that disorder, e.g., defects or phonons, increases electron energy relaxation rates.
飞秒时间分辨光发射技术对高度取向热解石墨（HOPG）中光激发电子的研究，为赝粒子（QP）寿命的各向异性提供了有力证据。QP寿命在1.1至1.5电子伏特之间（即石墨能带结构中鞍点附近）的能量依赖性存在明显异常，这表明了这种各向异性。这一现象得到了最近的从头算计算以及与富含缺陷的HOPG实验对比结果的支持，这些研究表明无序（如缺陷或声子）会提高电子能量弛豫速率。
