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Tuesday, March 21, 2017
Abstract-Instantaneous charge and dielectric response to terahertz pulse excitation in TTF-CA
Hiroki Gomi, Naoto Yamagishi, Tomohito Mase, Takeshi J. Inagaki, and Akira Takahashi
We present the results of exact numerical calculations of the dielectric properties of tetrathiafulvalene--chloranil (TTF-CA) using the extended Hubbard model. The electronic polarization of the ionic ground state is obtained by directly calculating the adiabatic flow of current. The direction of is opposite to polarization owing to ionic displacement, and is much larger than , showing that, in the ionic phase, TTF-CA is an electric ferroelectric. Furthermore, we numerically calculate the dynamics induced by THz pulse excitation. In the ionic phase, there exists an almost exact linear relationship between and , and between and in the realistic range of the excitation magnitude, where is the charge transfer (electric polarization) variation induced by the THz pulse and is the electric field of the pulse at time . The absolute value of in the neutral phase is much smaller than that in the ionic phase. These results are consistent with those of experiments and originate from the adiabatic nature of the THz pulse excited state.