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arXiv · 2203.07393

Probing the bulk plasmon continuum of layered materials through electron energy loss spectroscopy in a reflection geometry

Christian Boyd·Luke Yeo·Philip W. Phillips
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Abstract

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 relevant 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.

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Christian Boyd, Luke Yeo, Philip W. Phillips. 2022-08-18. Probing the bulk plasmon continuum of layered materials through electron energy loss spectroscopy in a reflection geometry. https://doi.org/10.1103/physrevb.106.155152

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