Ultrafast response of plasma-like reflectivity edge in (TMTTF)2AsF6   driven by 7-fs, 1.5-cycle strong-light field
  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. 
Y. Naitoh, Y. Kawakami, T. Ishikawa, Y. Sagae, H. Itoh, K. Yamamoto,   T. Sasaki, M. Dressel, S. Ishihara, Y. Tanaka, K. Yon...
cond-mat.str-el