Energy Dependence of Electron Lifetime in Graphite Observed with Femtosecond Photoemission Spectroscopy

Xu, Sheng; Cao, Jianming; Miller, Carl C.; Mantell, D. A.; Miller, R. J. Dwayne; Gao, Yongli

doi:10.1103/physrevlett.76.483

Cited by 130 publications

(147 citation statements)

References 21 publications

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“…By tting the numerically calculated hot-carrier dynamics, the energy relaxation time τ ( ) of the photoexcited carriers is obtained. Figure 5.7 shows the calculated carrier scattering time τ ( ) as a function of carrier energy for pristine graphene at a substrate temperature of 300 K. The carrier scattering time is precisely inverse to the carrier energy, τ ( ) = β/| | (with β ≈ 0.9 eVps), over a very broad energy range (| | ∼ 0.2 − 1.5 eV) in agreement with previous experimental studies on MEG [23] and graphite [120,121]. These results are in contrast with the linear relation on carrier energy, τ ( ) = α| |, [122,123] that is inferred from electrical transport measurements in some graphene samples.…”

Section: Shortcoming Of the Drude Modelsupporting

confidence: 74%

Relaxation Dynamics in Graphene

Malić

Knorr

2013

Graphene and Carbon Nanotubes

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In this thesis, the relaxation dynamics of nonequilibrium carriers in graphene is investigated. Based on the density matrix approach, the interaction of carriers with light, phonons and electrons is theoretically modelled. The resulting time-, momentum-, and angle-resolved simulation of the carrier dynamics enables the interpretation of recent experimental observations. Typically, the carrier relaxation has been accessed via high-resolution pump-probe experiments. Common to all studies is a bi-exponential decay of the pump-induced differential transmission (DT) spectrum. The fast decay component in the range of few tens of femtoseconds is assigned to an ultrafast Coulomb-dominated carrier redistribution towards a hot Fermi-Dirac distribution, whereas the slower decay component in the range of a picosecond reflects the equilibration between the electron and the phonon system. However, many studies report a zero-crossing after the initial decay in the transient DT spectrum, where the second decay component characterizes the recovering of the DT signal. In very good agreement with recent pump-probe experiment performed by the group of Prof. Manfred Helm (Helmholtz-Zentrum Dresden-Rossendorf), a microscopic explanation for the occurrence of transient negative differential transmission in graphene is found, where a detailed interplay of intraand interband absorption processes on the transient DT in graphene is investigated. In particular, phonon-assisted intraband processes are shown to lead to an enhanced absorption giving rise to the experimentally observed zero-crossing from positive to negative DT signals.In collaboration with the group of Prof. Theodore B. Norris (Michigan University, USA), theoretical studies combined with ultrafast time-resolved THz spectroscopy were performed to systematically investigate the hot-carrier dynamics in an array of graphene samples. The theory calculates explicitly the time-dependent response of the system to a THz probe pulse. The calculations reveal that the observed dynamics can be accounted for qualitatively without including any fitting parameters, phenomenological models or extrinsic effects. Specifically, the hot-carrier dynamics are governed by the coupling of extraordinarily efficient carrier-carrier and carrier-phonon interactions. Furthermore, the theory demonstrates that the simple Drude model is insufficient to fully account for the THz interactions.Beside pump-probe studies, the thesis presents the absorption spectra of mono-and bilayer graphene including the impact of the fully momentum-dependent optical and Coulomb matrix elements. In agreement with recent experiments, the absorbance of graphene is characterized by a frequency-independent value in the near-infrared spectral region and a pronounced peak in the ultraviolet region resulting from interband transition. In contrast to the linear band structure of graphene, the energy dispersion of bilayer graphene exhibits four parabolic bands resulting in interesting optical features: The absorbance exhibits in...

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Section: Shortcoming Of the Drude Modelsupporting

confidence: 74%

Relaxation Dynamics in Graphene

Malić

Knorr

2013

Graphene and Carbon Nanotubes

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“…Hot electron dynamics in graphene and graphite have been investigated by optical, THz, photoemission, and theoretical methods [1][2][3][4][5][6][7][8][9]23,34,[39][40][41][42][43][44][45][46]. Xu et al [39] first applied ultrafast time-resolved two-photon photoemission (TR-2PP) spectroscopy to excite a hot electron population and monitor its energy-dependent decay in graphite.…”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…Xu et al [39] first applied ultrafast time-resolved two-photon photoemission (TR-2PP) spectroscopy to excite a hot electron population and monitor its energy-dependent decay in graphite. Deviations of hot electron lifetimes from simple predictions of the Fermi liquid theory stimulated interest in the novel electron scattering properties of 2D materials [39,47,48]. Subsequent TR-2PP experiments and theoretical calculations found that the anisotropic band structure of graphite significantly constrains the phase space for electron-electron (e-e) scattering [23,41].…”

Section: Introductionmentioning

confidence: 99%

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Ultrafast Multiphoton Thermionic Photoemission from Graphite

et al. 2017

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Electronic heating of cold crystal lattices in nonlinear multiphoton excitation can transiently alter their physical and chemical properties. In metals where free electron densities are high and the relative fraction of photoexcited hot electrons is low, the effects are small, but in semimetals, where the free electron densities are low and the photoexcited densities can overwhelm them, the intense femtosecond laser excitation can induce profound changes. In semimetal graphite and its derivatives, strong optical absorption, weak screening of the Coulomb potential, and high cohesive energy enable extreme hot electron generation and thermalization to be realized under femtosecond laser excitation. We investigate the nonlinear interactions within a hot electron gas in graphite through multiphoton-induced thermionic emission. Unlike the conventional photoelectric effect, within about 25 fs, the memory of the excitation process, where resonant dipole transitions absorb up to eight quanta of light, is erased to produce statistical Boltzmann electron distributions with temperatures exceeding 5000 K; this ultrafast electronic heating causes thermionic emission to occur from the interlayer band of graphite. The nearly instantaneous thermalization of the photoexcited carriers through Coulomb scattering to extreme electronic temperatures characterized by separate electron and hole chemical potentials can enhance hot electron surface femtochemistry, photovoltaic energy conversion, and incandescence, and drive graphite-to-diamond electronic phase transition.

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“…in several analyses carried out for such systems, the e-e interaction is taken actually as short-range (TL model). As we discussed in previous papers 23 , the effects of the long-range Coulomb interaction have been shown to lead in general to unconventional electronic properties 24 and also to be responsible for a strong attenuation of the quasiparticle weight in graphite 25 .…”

Section: Introductionmentioning

confidence: 99%

Magnetic field effects and renormalization of the long-range Coulomb interaction in carbon nanotubes

Bellucci¹,

Onorato²

2006

Annals of Physics

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We develop two theoretical approaches for dealing with the low-energy effects of the repulsive interaction in one-dimensional electron systems. Renormalization Group methods allow us to study the low-energy behavior of the unscreened interaction between currents of well-defined chirality in a strictly one-dimensional electron system. A dimensional regularization approach is useful, when dealing with the low-energy effects of the long-range Coulomb interaction. This method allows us to avoid the infrared singularities arising from the long-range Coulomb interaction at D = 1. We can also compare these approaches with the Luttinger model, in order to analyze the effects of the short range term in the interaction.Thanks to these methods, we are able to discuss the effects of a strong magnetic field B in quasi one-dimensional electron systems, by focusing our attention on Carbon Nanotubes. Our results imply a variation with B in the value of the critical exponent α for the tunneling density of states, which is in fair agreement with that observed in a recent transport experiment involving carbon nanotubes. The dimensional regularization allows us to predict the disappearance of the Luttinger liquid, when the magnetic field increases, with the formation of a chiral liquid with α = 0.PACS numbers: 72.80.Rj

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Energy Dependence of Electron Lifetime in Graphite Observed with Femtosecond Photoemission Spectroscopy

Cited by 130 publications

References 21 publications

Relaxation Dynamics in Graphene

Relaxation Dynamics in Graphene

Ultrafast Multiphoton Thermionic Photoemission from Graphite

Magnetic field effects and renormalization of the long-range Coulomb interaction in carbon nanotubes

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