Two Holes in the t-J Model Form a Bound State for Any Nonzero J/t

Determination of the parameter regime in which two holes in the t-J model form a bound state represents a long standing open problem in the field of strongly correlated systems. By applying and systematically improving the exact diagonalization method defined over a limited functional space (EDLFS), we show that the average distance between two holes scales as < d > similar to 2(J/t)(-1/4) for J/t < 0.15, therefore, providing strong evidence that two holes in the t-J model form the bound state for any nonzero J/t. However, the symmetry of such bound pair in the ground state is p-wave. This state is consistent with phase separation at finite hole filling, as observed recently in Phys. Rev. B 85, 245113 (2012).