High-energy magnon dispersion in the half-filled Hubbard model:: A comparison with La2CuO4 -: art. no. 144420

We use quantum Monte Carlo methods and the single-mode approximation to study the magnon dispersion in the two-dimensional (2D) half-filled Hubbard and phonon-coupled Heisenberg models. We find that in the Hubbard model with U/t<8, the high-energy magnon dispersion is similar to that observed in inelastic neutron scattering experiments in La2CuO4. On the other hand, our studies of a 2D Heisenberg model coupled to dynamic optical bond phonons fail to reproduce the experimental dispersion. These results can be interpreted as evidence of intermediate U/t and charge fluctuations in the cuprate materials.