Ground-state phase diagram of a half-filled one-dimensional extended Hubbard model

The density-matrix renormalization group is used to study the phase diagram of the one-dimensional half-filled Hubbard model with on-site (U) and nearest-neighbor (V) repulsion and hopping t. A critical line V-c(U)approximate toU/2 separates a Mott insulating phase from a charge-density-wave phase. The formation of bound charge excitations for V>2t changes the phase transition from continuous to first-order at a tricritical point U(t)approximate to3.7t, V-t=2t. A frustrating effective antiferromagnetic spin coupling induces a bond-order-wave phase on the critical line V-c(U) for U-t