Band-renormalization Effect on Relationship between Superconductivity and Antiferromagnetism in t-J Model

Having cuprate superconductors in mind, we study a band-renormalization effect on a coexisting state of antiferromagnetism (AF) and superconductivity (SC) in a t-J model on a square lattice with a diagonal transfer t′ and three-site hopping terms, using a variational Monte Carlo method. It is found that this t-J model with t′/t = –0.3 exhibits coexistence of AF and SC orders in lightly doped regime and robust SC for a wide range of doping rate δ. This result contrasts with the previous results of a large-U/t Hubbard model, in which the two orders are mutually exclusive and a coexisting state does not appear; the SC state appears only in heavily doped regime (δ≳ 0.2), after the pure AF state vanishes at δ ∼ 0.2.