Domain walls in a doped antiferromagnet

The effects of a small amount of holes on the antiferromagnetic state of the two-dimensional Hubbard model are investigated analytically and numerically. It is found that it is energetically favorable for the system to form domain walls of finite width, with the holes localized in bound states at the walls. For a small but finite concentration of holes, a regularly spaced array of domain walls is formed, i.e. one has an insulating incommensurate antiferromagnet, with a linearly polarized magnetisation pattern and a modulation wavevector proportional to the hole concentration. With increasing electron-electron repulsion, the preferred orientation of the walls changes from parallel to a lattice direction to diagonal. Possible fluctuation effects in the incommensurate phase and relations with recent experiments on La2-xSrxCuO 4 are discussed.

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