  We consider the nonlinear terahertz response of n-doped monolayer graphene at
room temperature using a microscopic theory of carrier dynamics. Our
tight-binding model treats the carrier-field interaction in the length gauge,
includes phonon as well as short-range neutral-impurity scattering, and fully
accounts for the intrinsic nonlinear response of graphene near the Dirac point.
Treating each interaction microscopically allows us to separate contributions
from current clipping, phonon creation, and elastic impurity scattering.
Although neutral impurity scattering and phonon scattering are both highly
energy-dependent, we find that they impact conduction-band electron dynamics
very differently, and that together they can help explain experimental results
concerning field-dependent terahertz transmission through graphene.
