Dopant-Induced Plasmon Decay in Graphene

Novko, Dino

doi:10.1021/acs.nanolett.7b03553

Cited by 50 publications

(71 citation statements)

References 52 publications

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“…Despite the simplicity of the Einstein model, the trend of τ E and λ E is in good qualitative agreement with the result of first-principles calculations of Ref. 26.…”

Section: Approximate Treatment Of Electron-phonon Interactionsupporting

confidence: 85%

Phonon-assisted damping of plasmons in three- and two-dimensional metals

2018

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We investigate the effects of crystal lattice vibrations on the dispersion of plasmons. The loss function of the homogeneous electron gas (HEG) in two and three dimensions is evaluated numerically in presence of electronic coupling to an optical phonon mode. Our calculations are based on many-body perturbation theory for the dielectric function as formulated by the Hedin-Baym equations in the Fan-Migdal approximation. The coupling to phonons broadens the spectral signatures of plasmons in the electron-energy loss spectrum (EELS) and it induces the decay of plasmons on timescales shorter than 1 ps. Our results further reveal the formation of a kink in the plasmon dispersion of the 2D HEG, which marks the onset of plasmon-phonon scattering. Overall, these features constitute a fingerprint of plasmon-phonon coupling in the EELS of simple metals. It is shown that these effects may be accounted for by resorting to a simplified treatment of the electron-phonon interaction which is amenable to first-principles calculations.

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“…Despite the simplicity of the Einstein model, the trend of τ E and λ E is in good qualitative agreement with the result of first-principles calculations of Ref. 26.…”

Section: Approximate Treatment Of Electron-phonon Interactionsupporting

confidence: 85%

Phonon-assisted damping of plasmons in three- and two-dimensional metals

2018

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“…To reach this result, I adopted a diagrammatic analysis along with the Bethe-Salpeter equation for the phonon self-energy, an approach more commonly utilized for including the dynamical electron-phonon scattering mechanisms into an optical conductivity formula [43][44][45][46][47]. The above expression is equivalent to the intraband phonon self-energy derived in Refs.…”

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confidence: 99%

Nonadiabatic coupling effects in MgB2 reexamined

Novko

2018

Phys. Rev. B

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The unusual Raman spectrum of MgB2 and its formidable temperature dependence are successfully reproduced by means of a parameter-free ab initio nonadiabatic theory that accounts for the electron-hole pair scattering mechanisms with the system phonons. This example turns out to be a prototypical case where a strong nonadiabatic renormalization of the phonon frequency is partially washed out by the aforementioned scattering events, bringing along a characteristic temperature dependence. Both electron-hole pair lifetime and energy renormalization effects due to dynamical electron-phonon coupling turn out to play a crucial role. This theory could aid in comprehending other Raman spectra characterized with unconventionally strong electron-phonon interaction.Recent years have witnessed an ample interest in nonadiabatic (NA) coupling effects [1,2] and their intriguing impact on the vibrational properties of solids [3]. Particularly strong deviations from the adiabatic phonon spectrum were observed for the long wavelength (q ≈ 0) modes of carbon-based materials, such as metallic carbon nanotubes [4,5], graphite intercalation compounds [6-9], graphene [10][11][12], and boron-doped diamond [13]. The corresponding NA theory based in first principles is well established and in most instances the calculated NA phonon frequencies complement the experiments quite accurately [6,10,14]. Remarkably, in MgB 2 , both the state-of-the-art adiabatic and NA descriptions break down. Namely, the Raman measurements reveal an unusually large linewidth of the E 2g phonon peaked at around 77 meV [15][16][17][18][19], which falls just between the adiabatic (67 meV) and NA (94 meV) values [6,14].In order to resolve this discrepancy numerous explanations emerged. A significant temperature dependence of the phonon spectrum lead numerous studies to ascribe the foregoing anomalies to the anharmonicity [20][21][22][23][24]. Conversely, it was shown that the phonon-phonon corrections constitute only a small portion of the E 2g phonon linewidth and the frequency shift, as well as bring about a minor temperature change [16,[25][26][27][28]. The effects of the electron relaxation processes (e.g., higher order electron-phonon scattering) on the phonon spectrum were also taken into consideration, since it was shown that high-frequency optical modes in metallic systems might be rather sensitive to these processes when q ≈ 0 [29][30][31][32][33][34][35]. In fact, few studies have qualitatively demonstrated that it is precisely this mechanism that prompts the breakdown of the standard adiabatic and NA theories in MgB 2 [6,16,19,27,36,37]. Nevertheless, a concomitant NA theory based in first principles that can resolve this controversy is still absent. Such an in-depth quantitative survey of the NA effects is of great fundamental interest, e.g., for comprehending superconductivity mechanisms, especially in MgB 2 , * dino.novko@gmail.com where the unusually strong interaction between the E 2g phonon and electrons is suspected to underly the electron pairing p...

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“…Furthermore, the low-energy absorption is decreased below the two times Fermi energy due to the Pauli blocking. For the 1.54% Li and 1.56% N concetrations the additional absorption peak appears below 0.5 eV that comes from the graphene-dopant interband transitions [63]. The temperature dependence is also slightly altered by presence of the dopant atom.…”

Section: Resultsmentioning

confidence: 95%

Phonon-assisted processes in the ultraviolet-transient optical response of graphene

Novko

Kralj

2019

npj 2D Mater Appl

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Many recent experiments investigated potential and attractive means of modifying many-body interactions in two-dimensional materials through time-resolved spectroscopy techniques. However, the role of ultrafast phonon-assisted processes in two-dimensional systems is rarely discussed in depth. Here, we investigate the role of electron-phonon interaction in the transient optical absorption of graphene by means of first-principles methods. It is shown at equilibrium that the phonon-assisted transitions renormalize significantly the electronic structure. As a result, absorption peak around the Van Hove singularity broadens and redshifts by around 100 meV. In addition, temperature increase and chemical doping are shown to notably enhance these phonon-assisted features. In the photoinduced transient response we obtain spectral changes in close agreement with the experiments, and we associate them to the strong renormalization of occupied and unoccupied π bands, which predominantly comes from the coupling with the zone-center E2g optical phonon. Our estimation of the Coulomb interaction effects shows that the phonon-assisted processes can have a dominant role even in the subpicosecond regime. arXiv:1911.04826v1 [cond-mat.mtrl-sci]

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Dopant-Induced Plasmon Decay in Graphene

Cited by 50 publications

References 52 publications

Phonon-assisted damping of plasmons in three- and two-dimensional metals

Phonon-assisted damping of plasmons in three- and two-dimensional metals

Nonadiabatic coupling effects in MgB2 reexamined

Phonon-assisted processes in the ultraviolet-transient optical response of graphene

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