Electron energy-loss spectroscopy: A versatile tool for the investigations of plasmonic excitations

Abstract

The inelastic scattering of electrons is one route to study the vibrational and electronic properties of materials. Such experiments, also called electron energy-loss spectroscopy, are particularly useful for the investigation of the collective excitations in metals, the charge carrier plasmons. These plasmons are characterized by a specific dispersion (energy-momentum relationship), which contains information on the sometimes complex nature of the conduction electrons in topical materials. In this review we highlight the improvements of the electron energy-loss spectrometer in the last years, summarize current possibilities with this technique, and give examples where the investigation of the plasmon dispersion allows insight into the interplay of the conduction electrons with other degrees of freedom.

Negative plasmon dispersion in 2H-NbS2beyond the charge-density-wave interpretation

“…[12] The stoichiometry was verified by standardless energy dispersive spectrometry using a Jeol JXA-8600 electron probe microanalyzer. The EELS measurements along GM crystallographic direction ( || [ ] q 100 ) were performed with a 172 keV spectrometer described in [30,31]. The momentum resolution was set to 0.04 Å −1 and the energy resolution to 85 meV.…”

Valley plasmonics in transition metal dichalcogenides

“…which is sensitive to both collective and single-particle excitations (visible as maxima in the EELS spectra) 34 . It is important to note that the RPA description of plasmonic properties involves solely Landau-damping processes due to excitations of single particle-hole pairs.…”

Superconductivity-induced changes in density-density correlation function enabled by Umklapp processes

“…[20], the electron energy loss spectroscopy (EELS) [25][26][27][28][29] should be the most ideal probe for the density-density correlation function. The cross section of EELS σ( q, ω) is typically interpreted as σ( q, ω) ∝ v 2 q Imχ( q, ω), where χ( q, ω) is the true density-density correlation function at ( q, ω) which is χ( q, ω) 11 in the present paper.…”