Ground-state phase diagram of an extended Hubbard chain with correlated hopping at half-filling

We consider a generalized Hubbard model with on-site interaction U, nearest-neighbor repulsion V, and nearest-neighbor hopping for spin sigma, which depends on the sum of particles m(<(sigma)over bar>) with opposite spin in the two sites involved. The hopping matrix elements are denoted by t(AA),t(AB),t(BB) for m(<(sigma)over bar>) = 0,1,2, respectively. For 0<t(AB)<t(AA) = t(BB), we have determined the regions of parameters for which the ground-state (GS) of the one-dimensional system is a charge-density wave (CDW), a spin-density wave (SDW), or a metal (M), using Hartree-Fock, exact diagonalization of finite chains and quantum Monte Carlo. The results agree qualitatively with the exactly solvable limit of t(AB) = 0. For 0<t(AB)<t(AA) = t(BB), the GS is a M for sufficiently low values of U and V. In contrast, when t(AA) + t(BB) - 2t(AB) = 0, our results suggest that the GS is either a CDW or a SDW, with the boundary between them lying near the line U = 2 V.