Calculation of the optical conductivity spectra of one-dimensional quarter-filled molecular conductors on the basis of a mean-field approximation

The optical conductivity spectra of one-dimensional quarter-filled molecular conductors are calculated at T=0 on the basis of the mean-field approximation applied to the extended Hubbard Hamiltonian. The calculated spectra exhibit a remarkable absorption band in the mid-infrared range. The spectral intensity obtained in this approximation is roughly consistent with that evaluated by Mila through the sum rule, except when the exciton formation due to the nearest neighbor Coulomb interaction (V) is dominant. The results are qualitatively consistent with experimental results.