STAGGERED-FIELD-INDUCED HOLE PAIRING IN ONE-DIMENSIONAL CORRELATED SYSTEMS

We examine the influence of a staggered magnetic field on states involving a few holes in the one-dimensional t-J and Hubbard models. We apply exact diagonalizations of small systems, an analytical treatment of an anisotropic model, and a high-field perturbation expansion. Our results suggest that even modest staggered fields, h << t, induce the formation of bound hole pairs in a broad range of parameters, in particular for J/t < 1 in the t-J model and for U/t > 1 in the Hubbard model. In the same regions, by studying the density-density correlations and the compressibility, we argue that many holes form a paired state and that phase separation does not occur.