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 {σ}, which depends on the sum of particles m_σ-|Am with opposite spin in the two sites involved. The hopping matrix elements are denoted by tAA,tAB,tBB for m_σ-|Am=0,1,2, respectively. For 0tAB{t}AA$=${t}BB$, we have determined the regions of parameters for which the ground-state (GS) of the one-dimensional system is a charge-density wave (CDW), a spin-density wave (SDW), or a metal (M), using Hartree-Fock, exact diagonalization of finite chains and quantum Monte Carlo. The results agree qualitatively with the exactly solvable limit of tAB=0. For 0tAB{t}AA$=${t}BB$, 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=2V.