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Journal Article

Tracking Primary Thermalization Events in Graphene with Photoemission at Extreme Time Scales

MPS-Authors
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Gierz,  Isabella
Ultrafast Electron Dynamics, Condensed Matter Dynamics Department, Max Planck Institute for the Structure and Dynamics of Matter, Max Planck Society;

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Calegari,  Francesca
Quantum Condensed Matter Dynamics, Condensed Matter Dynamics Department, Max Planck Institute for the Structure and Dynamics of Matter, Max Planck Society;

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Aeschlimann,  Sven
Ultrafast Electron Dynamics, Condensed Matter Dynamics Department, Max Planck Institute for the Structure and Dynamics of Matter, Max Planck Society;

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Chavez Cervantes,  Mariana
Ultrafast Electron Dynamics, Condensed Matter Dynamics Department, Max Planck Institute for the Structure and Dynamics of Matter, Max Planck Society;

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Cavalleri,  Andrea
Department of Physics, Clarendon Laboratory, University of Oxford;
Quantum Condensed Matter Dynamics, Condensed Matter Dynamics Department, Max Planck Institute for the Structure and Dynamics of Matter, Max Planck Society;

Fulltext (public)

1506.00120.pdf
(Preprint), 2MB

PhysRevLett.115.086803.pdf
(Publisher version), 405KB

Supplementary Material (public)
Citation

Gierz, I., Calegari, F., Aeschlimann, S., Chavez Cervantes, M., Cacho, C., Chapman, R. T., et al. (2015). Tracking Primary Thermalization Events in Graphene with Photoemission at Extreme Time Scales. Physical Review Letters, 115(8): 086803. doi:10.1103/PhysRevLett.115.086803.


Cite as: http://hdl.handle.net/11858/00-001M-0000-0028-1AA7-9
Abstract
Direct and inverse Auger scattering are amongst the primary processes that mediate the thermalization of hot carriers in semiconductors. These two processes involve the annihilation or generation of an electron-hole pair by exchanging energy with a third carrier, which is either accelerated or decelerated. Inverse Auger scattering is generally suppressed, as the decelerated carriers must have excess energies higher than the band gap itself. In graphene, which is gapless, inverse Auger scattering is, instead, predicted to be dominant at the earliest time delays. Here, <8  fs extreme-ultraviolet pulses are used to detect this imbalance, tracking both the number of excited electrons and their kinetic energy with time-and angle-resolved photoemission spectroscopy. Over a time window of approximately 25 fs after absorption of the pump pulse, we observe an increase in conduction band carrier density and a simultaneous decrease of the average carrier kinetic energy, revealing that relaxation is in fact dominated by inverse Auger scattering. Measurements of carrier scattering at extreme time scales by photoemission will serve as a guide to ultrafast control of electronic properties in solids for petahertz electronics.