Incommensurate Antiferromagnetism and Magnetic Domain Walls in the Two-Dimensional Hubbard Model

Abstract

The antiferromagnetism of the two-dimensional Hubbard model is investigated analytically and numerically in the vicinity of half-filling. It is found that for a small but finite concentration of holes a regularly spaced array of domain walls is formed, with the holes localized at the domain walls, i.e. one has an insulating incommensurate antifer romagnet, with a linearly polarized magnetisation pattern and a modulation wavevector proportional to the hole concentration. Above a critical concentration of holes, pockets of free carriers appear, coexisting with incommensurate antiferromagnetic order. Only at even higher hole concentration does the antiferromagnetism vanish completely. Based on a Landau expansion, the different possible antiferromagnetic states are discussed.