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. 2017 Jan 27;3(1):e1601192.
doi: 10.1126/sciadv.1601192. eCollection 2017 Jan.

Splashing transients of 2D plasmons launched by swift electrons

Xiao Lin  1 , Ido Kaminer  2 , Xihang Shi  3 , Fei Gao  3 , Zhaoju Yang  3 , Zhen Gao  3 , Hrvoje Buljan  4 , John D Joannopoulos  2 , Marin Soljačić  2 , Hongsheng Chen  5 , Baile Zhang  6
Affiliations

Splashing transients of 2D plasmons launched by swift electrons

Xiao Lin et al. Sci Adv. .

Abstract

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.

Keywords: 2D plasmons; EELS; Reyleigh jet; formation time; formation zone; graphene; splashing; transition radiation.

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Figures

Fig. 1
Fig. 1. Schematic of 2D plasmons launching with a swift electron penetrating through a graphene monolayer.
Lf1 and Lf2 are the lengths of the formation zone in the region above and below the graphene layer, respectively.
Fig. 2
Fig. 2. Time evolution of magnetic field Hφ(r¯,t) when a swift electron perpendicularly penetrates through a graphene monolayer.
The green dashed line represents graphene. The electron is located (A) above graphene, (B) at graphene, and (C) below graphene.
Fig. 3
Fig. 3. Time evolution of the deviation of the electron density from its average value on graphene plane δn(r¯,t) when a swift electron penetrates through a graphene monolayer.
The electron is located (A and B) above graphene, (C) at graphene, and (D to H) below graphene.
Fig. 4
Fig. 4. Energy dissipation during the plasmonic formation time.
(A) Time evolution of emitted photon energy and the induced field energy [related to the induced field strength (Eκ¯⊥,ω1,2)2]. (B) Energy spectra of graphene plasmons by taking t = ∞ in the lossless case and by taking t = Lf2/v in the lossy case.
See this image and copyright information in PMC

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