▎ 摘　　要

Using density-matrix theory, we microscopically calculate the relaxation dynamics of photoexcited electrons in graphene. Electron-phonon coupling leads to an initially ultrafast energy dissipation and to a nonthermal phonon occupation of the highest optical phonon modes. We also calculate the temporal evolution of the electronic temperature and find good agreement with recent experimental work. (c) 2007 American Institute of Physics.