SPIN EXCITATIONS OF THE EXTENDED T-J MODEL - NEUTRON-SCATTERING

Dynamical spin susceptibility, chi (q, omega), of the t-J model with transfer integrals of the extended spatial range has been evaluated based on the slave-boson mean-field theory for both LSCO- and YBCO-type Fermi surfaces. In the former, the width and height of the incommensurate (IC) peaks are seen to have strong dependences on omega and the temperature, T. Interestingly, and in agreement with experiments, the IC peaks at low energy become sharper in the singlet RVB state which, in our classification, corresponds to the superconducting state in the region of optimal doping. In the case of YBCO, the dependences on omega and T at q = Q = (pi, pi), the antiferromagnetic wave vector, have particular features which share common qualitative characteristics with the experimental findings.