Hole binding in Mott antiferromagnets: A DMRG study

The binding of injected holes in antiferromagnets is studied based on the density matrix renormalization group (DMRG) simulation for the t-J model on square ladders. It is shown that the binding strength is substantially enhanced in a spin background with a short-range spin correlation, in contrast to that with a quasi-long-range spin correlation. However, it is further found that the enhanced pairing strength diminishes once the phase string effect in the hopping term of the t-J ladders is switched off and a coherent quasiparticle behavior is restored for an unpaired single hole. General implications for the nature of pairing in doped Mott insulators will be also discussed.