  The strong light-field effect of (TMTTF)2AsF6 was investigated utilizing
1.5-cycle, 7-fs infrared pulses. The ultarfast (20 fs) and large (40%) response
of the plasma-like reflectivity edge (0.7 eV) was analyzed by the changes in
omega_p=sqrt(ne2/(epsilon_0*epsilon(infty)*m)} (n: number of charges in the 1/4
filled-band, m: mass of charge, epsilon(infty): dielectric constants for
high-frequency and vacuum, e: elementary charge). The 3% reduction in omega_p
is attributed to the 6% increase in m. Furthermore, 20 fs oscillation of
omega_p in the time domain indicates that the plasma-like edge is affected by
the charge gap (0.2 eV) nature. Theoretical calculations suggest that the
Coulomb repulsion plays an important role in the increase in m.
