Electrical conductivity of the narrow-half-filled-band Hubbard model with nearest-neighbor interaction

The recent theoretical work on the one-dimensional Hubbard model showed this to be inadequate to explain the properties of $n$-methyl phenazinium tetracyanoquino dimethane (NMP-TCNQ) in the regime of narrow bandwidth compared to Coulomb repulsion; however, it also supported the suggestion existing in the literature that it is possible to fit both the magnetic susceptibility and the low-$T$ activation energy of the electrical conductivity by introducing a temperature dependence in the parameters of the Hamiltonian. Since the Hubbard Hamiltonian neglects important interactions (long-range Coulomb repulsion, electron-lattice interaction, etc.), it is reasonable to think that these interactions may be responsible for this temperature dependence. In this paper I add to the Hubbard Hamiltonian a nearest-neighbor Coulomb interaction and calculate the electrical conductivity in the narrow-bandwidth regime.