Charge and dielectric response to terahertz pulses in the charge-ordered phase of

摘要： We investigated the dielectric properties of the charge-ordered phase of α-(BEDT-TTF)2I3 using exact numerical calculations of an extended Hubbard model. The electronic contribution to the electric polarization (electronic polarization) ˉP of the charge-ordered ground state is obtained by directly calculating the current when transfer integrals were changed adiabatically from symmetric integrals to integrals for the charge-ordered phase without inversion symmetry. The angle of ˉP from the positive b axis is 36?, which is consistent with experimental results and previous theoretical results based on density-functional theory. Furthermore, we numerically calculated the dynamics induced by terahertz- (THz-) pulse excitation. Both the THz-pulse-induced variation of the electronic polarization magnitude and that of the charge disproportionation that shows the charge-order amplitude are largest when the electric field of the THz pulse and ˉP have almost the same direction. This originates from the charge transfer through bond b2(cid:3) being dominant in both the adiabatic flow of the current and the THz-pulse excitation. These results reproduce important features of the experimental results of THz-pulse-induced dynamics.