Carrier Relaxation in Epitaxial Graphene Photoexcited Near the Dirac Point

Stephan Winnerl (1) , Milan Orlita (2, 3) , Paulina Plochocka (2) , Piotr Kossacki (2) , Marek Potemski (2) , Torben Winzer (4) , Ermin Malic (4) , Andreas Knorr (4) , Michael Sprinkle (5) , Claire Berger (6) , Walter A. de Heer (5) , Harald Schneider (1) , Manfred Helm (1)

1 HZDR - Helmholtz-Zentrum Dresden-Rossendorf
2 LNCMI-G - Laboratoire national des champs magnétiques intenses - Grenoble
3 Faculty of Mathematics and Physics [Praha/Prague]
4 TU - Technical University of Berlin / Technische Universität Berlin
5 School of Physics [Atlanta]
6 NEEL - QuantECA - Circuits électroniques quantiques Alpes

We study the carrier dynamics in epitaxially grown graphene in the range of photon energies from 10 - 250 meV. The experiments complemented by microscopic modeling reveal that the carrier relaxation is significantly slowed down as the photon energy is tuned to values below the optical phonon frequency, however, owing to the presence of hot carriers, optical phonon emission is still the predominant relaxation process. For photon energies about twice the value of the Fermi energy, a transition from pump-induced transmission to pump-induced absorption occurs due to the interplay of interband and intraband processes.

Domaines: Science des matériaux [cond-mat.mtrl-sci]

Stephan Winnerl, Milan Orlita, Paulina Plochocka, Piotr Kossacki, Marek Potemski, et al.. Carrier Relaxation in Epitaxial Graphene Photoexcited Near the Dirac Point. Physical Review Letters, 2011, 107 (23), pp.237401. ⟨10.1103/PhysRevLett.107.237401⟩. ⟨hal-00911222⟩