Symmetry of binding in doped antiferromagnets

Using variational wave functions the construction of which is based on the ''string'' or "spin bag" picture, we calculate the energies of two-hole sta tes classified according to the momentum and the different irreducible repr esentations of the C-4v point group. We study different ratios J/t, interes ting from the experimental viewpoint, and compare our results to exact diag onalization. The energetically most favorable pair symmetries are d(x2-y2) and p like. The mechanism of hole binding is the caterpillar-type motion of two holes connected by a string of spin defects, whereas the well-known "b roken bond" mechanism does not produce binding for t/J>0/4. [S0163-1829(98) 05442-3].