Population Inversion in Monolayer and Bilayer Graphene

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.

18 pages, 6 figures

References in corpus (7)

• Ultrafast Photoluminescence from Graphene
• Phonon anharmonicities in graphite and graphene
• Supercollision cooling in undoped graphene
• Electron-phonon coupling and electron self-energy in electron-doped graphene: calculation of angular resolved photoemission spectra
• Electron-Phonon Interactions in Graphene, Bilayer Graphene, and Graphite
• Temperature dependence of the anharmonic decay of optical phonons in carbon nanotubes and graphite
• Ultrafast carrier dynamics in pristine and FeCl3-intercalated bilayer graphene

Cited by in corpus (3)

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• Similar ultrafast dynamics of several dissimilar Dirac and Weyl semimetals
• Microscopic origin of the bolometric effect in graphene