Effects of spin fluctuations and superconductivity in quasi-one-dimensional organic conductors

We study the electronic states using the single band Hubbard model at half-filling. We treat the effects of the on-site Coulomb interaction by the fluctuation-exchange (FLEX) method, and calculate the phase diagram and physical properties. The calculated pressure dependence of the magnetic transition temperature coincides well with the experimental one. We also show that a pseudogap is formed in the density of states near the chemical potential and that the NMR relaxation rate increases on cooling in the low-temperature region, and that d-wave superconductivity appears next to the antiferromagnetic state.