  We calculate the electron excitation in cubic silicon carbide (3C-SiC) caused
by the intense femtosecond laser double pulses using time-dependent density
functional theory (TDDFT). We assume the electron distributions in the valence
band (VB) and the conduction band (CB) based on three different approaches to
determine the dependence of the plasma that is formed on the excitation by the
first pulse. First, we consider the simple double pulse irradiation, which does
not include the electron-electron collisions and relaxation. Second, we
consider the partially thermalized electronic state, in which the electron
temperatures and numbers in the VB and the CB are defined independently. This
assumption corresponds to the plasma before the electron-hole collisions
becomes dominant. The third approach uses the fully thermalized electron
distribution, which corresponds to a timescale of hundreds fs. Our results
indicate that the simple double pulse approach is the worst of the three, and
show that the plasma formation changes the efficiency of the excitation by the
second pulse. When the electron temperature decreases, the laser excitation
efficiency increases as a result.
