Perturbation study on the spin and charge susceptibilities of the two-dimensional Hubbard model

We investigate the spin and charge susceptibilities of the two-dimensional Hubbard model based upon the perturbative calculation in the strength of correlation U. For U comparable to a bare bandwidth, the charge susceptibility decreases near half filling as hole doping approaches zero. This behavior suggesting the precursor of the Mott-Hubbard gap formation cannot be obtained without the vertex corrections beyond the random-phase approximation. In the low-temperature region, the spin susceptibility deviates from the Curie-Weiss-like law and finally turns to decrease with the decrease of temperature. This spin-gap-like behavior originates from the van Hove singularity in the density of states. © 1996 The American Physical Society.