Ultrafast Carrier Dynamics in Graphene under a High Electric Field

Tani, Shuntaro; Blanchard, F.; Tanaka, Kōichiro

doi:10.1103/physrevlett.109.166603

Cited by 144 publications

(153 citation statements)

References 34 publications

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“…CM is crucial for graphene's application in photovoltaics and photodetectors, as it can maximize the number of carriers created for a given excitation/absorption process 49 . Even though some evidence of CM was reported by Tani et al 50 , here we experimentally access the time window and the spectral coverage where direct spectroscopic signatures of CM can be obtained. In Fig.…”

Section: Resultsmentioning

confidence: 99%

Ultrafast collinear scattering and carrier multiplication in graphene

et al. 2013

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Graphene is emerging as a viable alternative to conventional optoelectronic, plasmonic and nanophotonic materials. The interaction of light with charge carriers creates an out-ofequilibrium distribution, which relaxes on an ultrafast timescale to a hot Fermi-Dirac distribution, that subsequently cools emitting phonons. Although the slower relaxation mechanisms have been extensively investigated, the initial stages still pose a challenge. Experimentally, they defy the resolution of most pump-probe setups, due to the extremely fast sub-100 fs carrier dynamics. Theoretically, massless Dirac fermions represent a novel many-body problem, fundamentally different from Schrödinger fermions. Here we combine pump-probe spectroscopy with a microscopic theory to investigate electron-electron interactions during the early stages of relaxation. We identify the mechanisms controlling the ultrafast dynamics, in particular the role of collinear scattering. This gives rise to Auger processes, including charge multiplication, which is key in photovoltage generation and photodetectors.

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Section: Resultsmentioning

confidence: 99%

Ultrafast collinear scattering and carrier multiplication in graphene

et al. 2013

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“…[33][34][35] The energy corresponding to this electric field is about half the ionization energy of carbon atoms. However, real graphene also possesses s orbitals which can be affected by such a high-frequency field.…”

Section: Discussionmentioning

confidence: 99%

Merging of Dirac points and Floquet topological transitions in ac-driven graphene

2013

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We investigate the effect of an in-plane ac electric field coupled to electrons in the honeycomb lattice and show that it can be used to manipulate the Dirac points of the electronic structure. We find that the position of the Dirac points can be controlled by the amplitude and the polarization of the field for high-frequency drivings, providing a new platform to achieve their merging, a topological transition which has not been observed yet in electronic systems. Importantly, for lower frequencies we find that the multiphoton absorptions and emissions processes yield the creation of additional pairs of Dirac points. This provides an additional method to achieve the merging transition by just tuning the frequency of the driving. Our approach, based on Floquet formalism, is neither restricted to specific choice of amplitude or polarization of the field, nor to a low-energy approximation for the Hamiltonian.

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“…It has been predicted that interband carrier-carrier scattering, often called impact ionization or inverse Auger scattering, can result in carrier multiplication [15,20]. This interesting effect has recently been observed experimentally [8,19,21]. A Ti:sapphire laser served as a source for 30-fs pulses with a photon energy of 1.55 eV and a spectral width (full width at half maximum FWHM) of 0.20 eV (repetition rate 78 MHz, pulse energy ~3 nJ).…”

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confidence: 99%

Anisotropy of Excitation and Relaxation of Photogenerated Charge Carriers in Graphene

et al. 2014

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We investigate the polarization dependence of the carrier excitation and relaxation in epitaxial multilayer graphene. Degenerate pump-probe experiments with a temporal resolution of 30 fs are performed for different rotation angles of the pump-pulse polarization with respect to the polarization of the probe pulse. A pronounced dependence of the pump-induced transmission on this angle is found. It reflects a strong anisotropy of the pump-induced occupation of photogenerated carriers in momentum space even though the band structure is isotropic. Within 150 fs after excitation an isotropic carrier distribution is established. Our observations imply the predominant role of collinear scattering preserving the initially optically generated anisotropy in

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Ultrafast Carrier Dynamics in Graphene under a High Electric Field

Cited by 144 publications

References 34 publications

Ultrafast collinear scattering and carrier multiplication in graphene

Ultrafast collinear scattering and carrier multiplication in graphene

Merging of Dirac points and Floquet topological transitions in ac-driven graphene

Anisotropy of Excitation and Relaxation of Photogenerated Charge Carriers in Graphene

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