Charge gap of the quasi-one-dimensional organic conductors: A density-matrix renormalization-group study

The Density-matrix renormalization-group (DMRG) technique is used to study the one-dimensional (1D) dimerized Hubbard model at quarter filling. We carry out a precise calculation of the charge gap as a function of the interaction and dimerization strengths and evaluate the interaction strength of the effective 1D Hubbard model at half filling. We also examine the effect of nearest-neighbor repulsion on the charge gap, whereby Re evaluate the realistic repulsive strengths for quasi-1D organic compounds.