Geometric effect of high-resolution electron energy loss spectroscopy on the identification of plasmons: An example of graphene

Li, Jiade; Lin, Zijian; Miao, Guangyao; Weiliang, Zhong,; Xue, Siwei; Li, Yang; Tao, Zhiyu; Wang, Weihua; Guo, Jiandong; Zhu, Xuetao

doi:10.1016/j.susc.2022.122067

Cited by 5 publications

(2 citation statements)

References 60 publications

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“…In Bi-2212 [12,47,48] and Bi-2201 [12], HREELS measurements at long wavelengths have observed a broad responsei.e., broader than the plasmon peak in Bi-2212 inferred via optical means [12,[49][50][51] -across energies below the (bulk) optical plasma frequency. Unfortunately, the low energies of incident electrons in these HREELS experiments skews the spectrum at long wavelengths, rendering the precise surface loss function difficult to extract from an experimental intensity [12,52,53]. Including the small, but finite [54], out of plane conduction between copper oxide layers pushes the q → 0 acoustic plasma frequency to a finite value [13]; indeed, this state of affairs appears to be supported by RIXS [6][7][8][9].…”

Section: Discussionmentioning

confidence: 99%

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

Boyd¹,

Yeo²,

Phillips³

2022

Preprint

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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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Section: Discussionmentioning

confidence: 99%

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

Boyd¹,

Yeo²,

Phillips³

2022

Preprint

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“…It is noteworthy that, under certain conditions, neglecting the effects of the Coulomb matrix element can result in an artificially dispersing loss peak with dispersion velocity equal to the velocity of the incident probe electron (27.6 eV Å for a 50 eV electron). This artefact arises owing to the combination of geometry and the Coulomb matrix element, and only occurs when the magnitude of the probe electron’s momentum perpendicular to the surface is larger after scattering (that is, backward scattering) 41 . We avoid this geometric artefact by both dividing out the Coulomb matrix element and always working in the forward-scattering geometry where the magnitude of the outgoing momentum perpendicular to the surface is smaller after scattering 34 .…”

Section: Methodsmentioning

confidence: 99%

Pines’ demon observed as a 3D acoustic plasmon in Sr2RuO4

Husain

Huang

Mitrano

et al. 2023

Nature

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The characteristic excitation of a metal is its plasmon, which is a quantized collective oscillation of its electron density. In 1956, David Pines predicted that a distinct type of plasmon, dubbed a ‘demon’, could exist in three-dimensional (3D) metals containing more than one species of charge carrier1. Consisting of out-of-phase movement of electrons in different bands, demons are acoustic, electrically neutral and do not couple to light, so have never been detected in an equilibrium, 3D metal. Nevertheless, demons are believed to be critical for diverse phenomena including phase transitions in mixed-valence semimetals2, optical properties of metal nanoparticles3, soundarons in Weyl semimetals4 and high-temperature superconductivity in, for example, metal hydrides3,5–7. Here, we present evidence for a demon in Sr2RuO4 from momentum-resolved electron energy-loss spectroscopy. Formed of electrons in the β and γ bands, the demon is gapless with critical momentum qc = 0.08 reciprocal lattice units and room-temperature velocity v = (1.065 ± 0.12) × 105 m s−1 that undergoes a 31% renormalization upon cooling to 30 K because of coupling to the particle–hole continuum. The momentum dependence of the intensity of the demon confirms its neutral character. Our study confirms a 67-year old prediction and indicates that demons may be a pervasive feature of multiband metals.

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

2022

View full text Add to dashboard Cite

Geometric effect of high-resolution electron energy loss spectroscopy on the identification of plasmons: An example of graphene

Cited by 5 publications

References 60 publications

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

Pines’ demon observed as a 3D acoustic plasmon in Sr2RuO4

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

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