Ultrafast Relaxation of Excited Dirac Fermions in Epitaxial Graphene Using Optical Differential Transmission Spectroscopy

Sun, Dong; Wu, Zhiyuan; Divin, Charles J.; Li, Xuebin; Berger, Claire; Heer, Walt A. de; First, Phillip N.; Norris, Theodore B.

doi:10.1103/physrevlett.101.157402

Cited by 469 publications

(484 citation statements)

References 27 publications

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“…The ultrafast carrier dynamics 23,124 , combined with large absorption and Pauli blocking make graphene an ideal ultra-broadband, fast SA. Compared to SESAMs and SWNTs, there is no need of bandgap engineering or chirality/diameter control.…”

Section: G Saturable Absorbers and Ultrafast Lasersmentioning

confidence: 99%

Graphene photonics and optoelectronics

et al. 2010

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The richness of optical and electronic properties of graphene attracts enormous interest. Graphene has high mobility and optical transparency, in addition to flexibility, robustness and environmental stability. So far, the main focus has been on fundamental physics and electronic devices. However, we believe its true potential to be in photonics and optoelectronics, where the combination of its unique optical and electronic properties can be fully exploited, even in the absence of a bandgap, and the linear dispersion of the Dirac electrons enables ultra-wide-band tunability. The rise of graphene in photonics and optoelectronics is shown by several recent results, ranging from solar cells and light emitting devices, to touch screens, photodetectors and ultrafast lasers. Here we review the state of the art in this emerging field.

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Section: G Saturable Absorbers and Ultrafast Lasersmentioning

confidence: 99%

Graphene photonics and optoelectronics

et al. 2010

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“…For some of the experiments, the negative DT can be clearly traced back to the predominant intraband absorption. This is the case, when the photon energy is smaller than twice the value of the Fermi energy [23,81,85]. However, for all other cases, where negative DT components occur for photon energies much larger than the Fermi energy, the underlying mechanism has been controversially discussed in literature.…”

Section: Impact Of Intraband Absorption In Graphenementioning

confidence: 90%

“…This allows to study the THz dynamics for di erent doping levels and di erent degrees of disorder. The MEG samples are highly n-doped (ε F ∼ 100 − 400 meV) due to electron transfer from the interface, and the Fermi level in subsequent layers decreases exponentially away from the substrate to around ε F ∼ 10 meV [81,85,115,116].…”

Section: Optical Pump and Thz Probe DI Erential Transmission Spectramentioning

confidence: 99%

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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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“…Moreover, we take e 1 ¼ 1 and e 2 ¼ 1:5 for an air/TLG/SiO 2 system, where the effect of the dielectric constant mismatch between TLG and the substrate layer has been taken into account [30]. It has been obtained experimentally [31] that in a graphene device, the energy relaxation time is about t $ 1 ps for high-density samples. Thus, we take t $ 1 ps in the calculations.…”

Section: A Simplified Modelmentioning

confidence: 99%

Optoelectronic properties of ABC‐stacked trilayer graphene

Xiao

Zhang

et al. 2012

Physica Status Solidi (b)

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We present a theoretical study on the optoelectronic properties of ABC-stacked trilayer graphene (TLG). The optical conductance and light transmittance are evaluated through using the energy-balance equation derived from the Boltzmann equation for an air/graphene/dielectric-wafer system in the presence of linearly polarized radiation field. The results obtained from two band structure models are examined and compared. For short wavelength radiation, the universal optical conductance s 0 ¼ 3e 2 =ð4hÞ can be obtained. Importantly, there exists an optical absorption window in the radiation wavelength range 10-200 mm, which is induced by different transition energies required for inter-and intra-band optical absorption channels. As a result, we find that the position and width of this window depend sensitively on temperature and carrier density of the system, especially the lower frequency edge. There is a small characteristic absorption peak at about 82 mm where the largest interband transition states exist in the ABC-stacked TLG model, in contrast to the relatively smooth curves in a simplified model. These theoretical results indicate that TLG has some interesting and important physical properties which can be utilized to realize infrared or THz optoelectronic devices.

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Ultrafast Relaxation of Excited Dirac Fermions in Epitaxial Graphene Using Optical Differential Transmission Spectroscopy

Cited by 469 publications

References 27 publications

Graphene photonics and optoelectronics

Graphene photonics and optoelectronics

Relaxation Dynamics in Graphene

Optoelectronic properties of ABC‐stacked trilayer graphene

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