抄録
It is discussed on the fluctuation-exchange (FLEX) approximation that the charge susceptibility χc increases divergently in the 2D t–t′ Hubbard model near the half-filling as the strength of the onsite Coulomb interaction U is approached to the critical value Ucr for the critical point to onset of the antiferromagnetic (AF) order. It turns out that the main origin of the divergence of χc is the Aslamazov–Larkin (AL) type contribution which can be taken into account by the FLEX approximation and is enhanced by the strong AF correlations because two AF-fluctuation modes and the vertex corretions work cooperatively to enhance χc. Indeed, AL-type contribution almost exhausts the enhanced part of χc in the region U\\simeqUcr. This result is consistent with experimental observations in under-doped cuprates LSCO and quantum Monte Carlo simulations by Furukawa and Imada [J. Phys. Soc. Jpn. 62 (1993) 2557].
