Fig. 1. Photoexcitation dynamics and corresponding carrier distributions in graphene.

(i) Interband optical excitation leads to nonthermal electron-hole distribution. (ii) Electrons and holes each evolve into separate quasi-thermalized hot FD distributions with distinct temperatures ($T_{e(h)}^{*}$) and chemical potentials ($T_{e(h)}^{*}$) in ~10 fs, mostly through electron-electron intraband scattering. (iii and iv) Interband scattering across the Dirac point and optical phonon emission establish hot thermalized electron distribution with one temperature (T_e) and chemical potential (μ) in ~100 fs, which cools down further through emission of optical and acoustic phonons in picoseconds.