High-energy magnon dispersion in the half-filled Hubbard model: A comparison withLa2CuO4

Abstract

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 ${\mathrm{La}}_{2}{\mathrm{CuO}}_{4}.$ 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.