  Ultrafast carrier dynamics of pristine bilayer graphene (BLG) and bilayer
graphene intercalated with FeCl3 (FeCl3-G), were studied using time-resolved
transient differential reflection (delta R/R). Compared to BLG, the FeCl3-G
data showed an opposite sign of delta R/R, a slower rise time, and a single
(instead of double) exponential relaxation. We attribute these differences in
dynamics to the down-shifting of the Fermi level in FeCl3-G, as well as the
formation of numerous horizontal bands arising from the d-orbitals of Fe. Our
work shows that intercalation can dramatically change the electronic structure
of graphene, and its associated carrier dynamics.
