Accurate Computation of the Magnetic Susceptibility for the Normal Phase of Organic Conductors

The magnetic susceptibility of the quarter-filled one-dimensional extended Hubbard model is calculated using the density-matrix renormalization group technique. It is found that in the charge gap regime of the model ($U>4t$ and $V > 2t$), or in the metallic region with important superconductive fluctuations ($U<4t$ and $V>2t$), $\chi (T)$ displays a singularity at T=0 and an inflection point at low temperatures that are similar to what occurs in the spin-half quantum spin chain. These results, whose accuracy outdoes that of any other available technique, are useful data which allow a comparison between theory and experiment in the normal phase of the organic conductors.