Valence-electron excitations in the alkali metals

Felde, A. vom; Sprösser-Prou, J.; Fink, J.

doi:10.1103/physrevb.40.10181

Cited by 192 publications

(193 citation statements)

References 67 publications

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“…e p 0 5:6 0:2 eV, which is found to be in agreement with ! EELS p 0 5:77 eV [25]. Furthermore, the dispersion constant 0:21 0:02 is in line with the corresponding theoretical value of 0:22 obtained from the results of the calculations performed for the Na pl-pl excitation.…”

supporting

confidence: 70%

Correlation-Induced Double-Plasmon Excitation in Simple Metals Studied by Inelastic X-Ray Scattering

et al. 2005

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We report a new type of peaklike structure observed in the tail of the dynamic structure factor of simple metals, measured by inelastic x-ray scattering. Based on the momentum-transfer dependence of the energy position and the intensity of this structure, it has been unambiguously attributed to intrinsic plasmonplasmon excitations, an electronic correlation effect that was theoretically predicted by many-body perturbation theory of the homogeneous-electron-gas model beyond the random-phase approximation. This signature appears to be largely unaffected by electron-ion interaction effects. Thus a structure that is primarily caused by correlation effects in the electron gas has been found experimentally in the dynamic structure factor of simple metals. DOI: 10.1103/PhysRevLett.95.157401 PACS numbers: 78.70.Ck, 71.10.Ca, 71.45.2d The appropriate theoretical treatment of correlation in an interacting electron gas at metallic densities still remains a challenge in spite of the large amount of work on this topic. Therefore, experimental methods that can directly test theoretical predictions are very valuable. For systems that closely resemble a homogeneous electron gas (jellium), measurements of the dynamic structure factor S q; ! as a function of the momentum transfer q and the energy loss ! offer such a testing ground of correlation effects, since S q; ! is the Fourier transform in space and time of the density-density correlation function [1]. Inelastic x-ray scattering (IXS) is the favorable experimental method to study S q; ! for large momentum transfers q [2], i.e., when short-range correlations are probed. In particular, the advantage of IXS is the nearly complete absence of multiple scattering in contrast to electron energy-loss spectroscopy (EELS) [3], because in EELS extrinsic multiple excitations can obscure the information on electron correlations. IXS studies on simple metals [4] clearly showed significant deviations of the overall shape of S q; ! for large q from the shape predicted by the jellium model in the random-phase approximation (RPA) [5]. The RPA is known to incorporate long-range correlations only and thus for small q jqj approximately accounts for the energy position and dispersion of collective excitations such as plasmons in simple metals. In both cases the influence of the effective electron-ion interaction is found to be small. For larger q the deviations of the experimental observations from the RPA jellium calculations exhibit three characteristic features: (i) the centroid of S q; ! as a function of ! is shifted to lower energy losses [4]; (ii) a double-peak or a one-peak-one-shoulder structure appears to be universal for all simple metals [5]; (iii) the S q; ! spectra show tails for ! far beyond the upper limit of the jellium (single) particle-hole excitation spectrum [6,7].All three observed features were attributed to correlation effects beyond the RPA [4,[8][9][10][11][12][13]. However, the ion potential was found to cause similar effects [13][14][15][16][17][18]. As a result, it...

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confidence: 70%

Correlation-Induced Double-Plasmon Excitation in Simple Metals Studied by Inelastic X-Ray Scattering

et al. 2005

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“…18 and 19͒, or the exact dispersion relation of the plasmon, especially in certain anomalies such as the negative dispersion in cesium. 5,7,8,11,20 While for q → 0, the observed small shift of the plasmon energy compared to its RPA value is due to the bandstructure effects and core polarization, the increase in linewidth with an increasing q is a combined effect of the crystal potential and dynamical correlations, as has been demonstrated for Al. 21 By studying the more detailed fine structure of the plasmon lineshape, it was also predicted that the socalled double-plasmon excitations ͑henceforth labeled as plpl͒ should cause an additional peaklike structure on the high energy side of the plasmon line.…”

Section: Introductionmentioning

confidence: 65%

“…4 One of the canonical applications of the studies of the correlation effects in a many-electron system is the dynamics of valence electrons in a nearly free-electron gas. The corresponding fundamental excitation experimentally observed in a simple metal at a small momentum transfer is the plasmon, [5][6][7][8] which is a collective excitation of the valence electrons caused by the long range Coulomb interaction and qualitatively understood within the RPA of the FEG.…”

Section: Introductionmentioning

confidence: 99%

“…In both cases, the scattering cross section is proportional to the dynamic structure factor S͑q , ͒, where q is the momentum and is the energy transferred to the electron system under study. In many experiments, the attention has been focused on the plasmon dispersion 5,6,11 but, especially in systems not resembling the FEG, the fine structure of the S͑q , ͒ gives important information on many-body and band-structure-related effects. [12][13][14][15][16][17] However, even when applied to the FEG, the RPA cannot explain, for example, the finite linewidth, which is found to increase with the increasing q = ͉q͉ ͑Refs.…”

Section: Introductionmentioning

confidence: 99%

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Electron-density dependence of double-plasmon excitations in simple metals

et al. 2008

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Double plasmons are unique fingerprints of dynamical correlations in the model of a free-electron gas beyond the random phase approximation. A combined experimental and theoretical study of double-plasmon excitations in three simple metals Na, Mg, and Al is presented. The intensities, spectral shapes, and dispersions of these excitations are analyzed as a function of momentum. The measured double-plasmon intensity is found to increase with a decreasing electron density, which is in good agreement with the expectations of strength of the correlation effects as a function of the electron gas density. The overall quantitative agreement between the experimental and the theoretical results is very good, while the remaining discrepancies may be due to higher order correlation effects and band-structure effects.

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“…For most materials, the plasmon frequency lies in the visible region and disperses at moderate rate as a function of momentum q [23]. At larger momentum values, the effect of electronic exchange correlation becomes stronger [25]. The prediction of the precise shape of the dispersion curve and its lifetime has long been an intricate problem in condensed matter physics as well as in plasma physics, and still remains a theoretical challenge [11,26,27].…”

Section: Fundamental Properties Of Plasmons Probed By Electron Energymentioning

confidence: 99%

Plasmons in nanoscale and atomic-scale systems

Nagao

Han

Hoang

et al. 2010

Science and Technology of Advanced Materials

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Plasmons in metallic nanomaterials exhibit very strong size and shape effects, and thus have recently gained considerable attention in nanotechnology, information technology, and life science. In this review, we overview the fundamental properties of plasmons in materials with various dimensionalities and discuss the optical functional properties of localized plasmon polaritons in nanometer-scale to atomic-scale objects. First, the pioneering works on plasmons by electron energy loss spectroscopy are briefly surveyed. Then, we discuss the effects of atomistic charge dynamics on the dispersion relation of propagating plasmon modes, such as those for planar crystal surface, atomic sheets and straight atomic wires. Finally, standing-wave plasmons, or antenna resonances of plasmon polariton, of some widely used nanometer-scale structures and atomic-scale wires (the smallest possible plasmonic building blocks) are exemplified along with their applications.

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Valence-electron excitations in the alkali metals

Cited by 192 publications

References 67 publications

Correlation-Induced Double-Plasmon Excitation in Simple Metals Studied by Inelastic X-Ray Scattering

Correlation-Induced Double-Plasmon Excitation in Simple Metals Studied by Inelastic X-Ray Scattering

Electron-density dependence of double-plasmon excitations in simple metals

Plasmons in nanoscale and atomic-scale systems

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