Incommensurate charge correlation and phase diagram of the one-dimensional superlattice Hubbard model at half-filling

We study the phase diagram of a half-filled one-dimensional superlattice Hubbard model with an alternating orbital energy +/-epsilon/2 and on-site Coulomb repulsion U-A and U-B using the density-matrix renormalization group and finite-size scaling analysis. For U-A >> U-B, we observe an incommensurate charge correlation phase. For U-B = 0, we find a transition from the band insulating phase to the correlated metallic phase at the critical point epsilon = U-A/2. For U-B > 0, we find three insulating phases as in the ionic Hubbard model. In the gapless region, the correlation functions exhibit the asymptotic behavior of power-law decay as in the Tomonaga-Luttinger liquid.