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Population inversion in monolayer and bilayer graphene

MPS-Authors
/persons/resource/persons133795

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

/persons/resource/persons133781

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

/persons/resource/persons133811

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

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Fulltext (public)

1409.0211v1.pdf
(Preprint), 3MB

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Citation

Gierz, I., Mitrano, M., Petersen, J. C., Cacho, C., Turcu, I. C. E., Springate, E., et al. (2015). Population inversion in monolayer and bilayer graphene. Journal of Physics: Condensed Matter, 27(16): 164204. doi:10.1088/0953-8984/27/16/164204.


Cite as: http://hdl.handle.net/11858/00-001M-0000-0026-B0D5-F
Abstract
The recent demonstration of saturable absorption and negative optical conductivity in the Terahertz range in graphene has opened up new opportunities for optoelectronic applications based on this and other low dimensional materials. Recently, population inversion across the Dirac point has been observed directly by time- and angle-resolved photoemission spectroscopy (tr-ARPES), revealing a relaxation time of only ~130 femtoseconds. This severely limits the applicability of single layer graphene to, for example, Terahertz light amplification. Here we use tr-ARPES to demonstrate long-lived population inversion in bilayer graphene. The effect is attributed to the small band gap found in this compound. We propose a microscopic model for these observations and speculate that an enhancement of both the pump photon energy and the pump fluence may further increase this lifetime.