FLEX study on enhanced charge susceptibility near antiferromagnetic mott transition in two-dimensional t-t′ Hubbard model

It is discussed on the fluctuation-exchange (FLEX) approximation that the charge susceptibility χ_c 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 U_cr for the critical point to onset of the antiferromagnetic (AF) order. It turns out that the main origin of the divergence of χ_c 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 χ_c. Indeed, AL-type contribution almost exhausts the enhanced part of χ_c in the region U ≃ U_cr. 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].