State Key Laboratory of Modern Optical Instrumentation, Zhejiang University, Hangzhou 310027, China.; Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
Sci Adv. 2017 Jan 27;3(1):e1601192. doi: 10.1126/sciadv.1601192. eCollection 2017 Jan.
Launching of plasmons by swift electrons has long been used in electron energy-loss spectroscopy (EELS) to investigate the plasmonic properties of ultrathin, or two-dimensional (2D), electron systems. However, the question of how a swift electron generates plasmons in space and time has never been answered. We address this issue by calculating and demonstrating the spatial-temporal dynamics of 2D plasmon generation in graphene. We predict a jet-like rise of excessive charge concentration that delays the generation of 2D plasmons in EELS, exhibiting an analog to the hydrodynamic Rayleigh jet in a splashing phenomenon before the launching of ripples. The photon radiation, analogous to the splashing sound, accompanies the plasmon emission and can be understood as being shaken off by the Rayleigh jet-like charge concentration. Considering this newly revealed process, we argue that previous estimates on the yields of graphene plasmons in EELS need to be reevaluated.
快速电子激发等离激元在电子能量损失谱（EELS）中被广泛用于研究超薄或二维（2D）电子系统的等离激元性质。然而，快速电子在空间和时间上如何产生等离激元的问题从未得到解答。我们通过计算和演示在石墨烯中二维等离激元的产生的时空动力学来解决这个问题。我们预测了一种类似于射流的过度电荷浓度的快速上升，这会延迟 EELS 中二维等离激元的产生，在发射波纹之前表现出类似于飞溅现象中的流体力学雷利射流。光子辐射类似于飞溅声，伴随着等离激元的发射，并且可以理解为被雷利射流状的电荷浓度甩开。考虑到这个新揭示的过程，我们认为需要重新评估以前在 EELS 中对石墨烯等离激元产量的估计。
