Berlin 2008 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 51: Poster IV

HL 51.27: Poster

Thursday, February 28, 2008, 16:30–19:00, Poster D

Phonon-induced carrier relaxation and hot phonon dephasing dynamics in graphene — •Frank Milde, Stefan Butscher, Ermin Malic, Matthias Hirtschulz, and Andreas Knorr — TU Berlin, Hardenbergstr. 36, D-10623 Berlin, Germany

We investigate the influence of the electron-phonon coupling (EPC) in graphene within the density-matrix formalism. To determine the EPC matrix elements Kohn anomalies in the phonon dispersions are used [1].

Our approach is used to microscopically calculate the relaxation dynamics of photoexcited electrons in graphene. Similar to recent experiments in graphite [2], hot phonons lead to a delayed decay of the electronic temperature. Our numerical simulations reproduce these observations [3] and give new insight into the ultrafast dynamics of the first 500 fs after excitation not yet accessible by the experiment. At these times an initially ultrafast energy dissipation and a non-thermal phonon occupation of the highest optical phonon modes are found. We also calculate the temporal evolution of the electronic temperature and find good agreement with recent experimental results [2].
[1] Piscanec et al., Phys. Rev. Lett. 93, 185503 (2004)

[2] Kampfrath et al., Phys. Rev. Lett. 95, 187403 (2005)

[3] Butscher et al., Appl. Phys. Lett. 91, 203103 (2007)