Magnetic correlation in the Hubbard model on a honeycomb lattice Original Research Article

The magnetic correlation in the Hubbard model on a honeycomb lattice is systematically studied by quantum Monte Carlo method. It is found that the magnetic order is qualitatively different in two filling regions separated by the Van Hove singularity around image. A short-ranged ferromagnetic correlation is found in the low filling region, which is enhanced slightly by the on-site Coulomb interaction. The ferromagnetic fluctuation depends sensitively on the filling but is strengthened markedly as the next-nearest hoping integral increases.