Possible existence of zero spin-sound in two-dimensional Hubbard model

The Landau parameter f(a)(0) in two-dimensional Hubbard model is calculated by the second-order perturbation method. It is shown that F-a(0) changes its sign from negative to positive as the filling is increased to the half-filling for the interaction U/t greater than or similar to 2.0. This means that the spin density waves propagation, zero spin-sound, is possible in the system described by Hubbard model near half-filling. It is shown that the spin susceptibility decreases for U/t greater than or similar to 2.0 when the half-filling is approached exhibiting the so-called spin-gap behavior. (C) 2000 Elsevier Science B.V. All rights reserved.