Probing the bulk plasmon continuum of layered materials through electron energy loss spectroscopy in a reflection geometry
Probing the bulk plasmon continuum of layered materials through electron energy loss spectroscopy in a reflection geometry
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DOI：
10.1103/physrevb.106.155152
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发表时间：
2022-03
影响因子：
3.7
通讯作者：
C. Boyd;L. Yeo;P. Phillips
中科院分区：
文献类型：
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作者：
C. Boyd;L. Yeo;P. Phillips
已知二维导电平面的周期性排列存在一种（体）等离激元色散，其根据面外波矢在三维金属典型的有能隙行为与无能隙的声学区域之间过渡。半无限体系——与反射几何结构下电子能量损失谱（EELS）相关的构型，如高分辨率电子能量损失谱（HREELS）中的情况——已知存在一种表面等离激元，在截止波矢以下停止传播。由于f和规则要求无论是否存在尖锐激发都要有有限响应，我们证明了表面损失函数（HREELS所探测的材料响应）中剩余的部分是无限体系（体）等离激元的贡献。特别地，我们给出了等离激元连续谱与表面损失函数中谱权重之间的一一映射。鉴于这一结果，我们建议将HREELS视为层状材料中等离激元连续谱的长波探针。
A periodic arrangement of 2D conducting planes is known to host a (bulk) plasmon dispersion that interpolates between the typical, gapped behavior of 3D metals and a gapless, acoustic regime as a function of the out-of-plane wavevector. The semi-infinite system — the configuration rele-vant to Electron Energy Loss Spectroscopy (EELS) in a reflection geometry, as in High Resolution EELS (HREELS) — is known to host a surface plasmon that ceases to propagate below a cutoff wavevector. As the f-sum rule requires a finite response whether or not there exist sharp excitations, we demonstrate that what remains in the surface loss function — the material response probed by HREELS — is the contribution from the (bulk) plasmon of the infinite system. In particular, we provide a one-to-one mapping between the plasmon continuum and the spectral weight in the surface loss function. In light of this result, we suggest that HREELS be considered a long wavelength probe of the plasmon continuum in layered materials.