arXiv:0812.0234 · Physical Review B
Tuning the bond-order wave phase in the half-filled extended Hubbard model
Manoranjan Kumar, S. Ramasesha, Z. G. Soos
Abstract
Theoretical and computational studies of the quantum phase diagram of the one-dimensional half-filled extended Hubbard model (EHM) indicate a narrow bond-order wave (BOW) phase with finite magnetic gap ${E}_{m}$ for on-site repulsion $U<{U}^{\ensuremath{\ast}}$, the critical point, and nearest-neighbor interaction ${V}_{c}\ensuremath{\approx}U/2$ near the boundary of the charge-density wave (CDW) phase. Potentials with more extended interactions that retain the EHM symmetry are shown to have a less cooperative CDW transition with higher ${U}^{\ensuremath{\ast}}$ and wider BOW phase. Density-matrix renormalization group is used to obtain ${E}_{m}$ directly as the singlet-triplet gap, with finite ${E}_{m}$ marking the BOW boundary ${V}_{s}(U)$. The BOW/CDW boundary ${V}_{c}(U)$ is obtained from exact finite-size calculations that are consistent with previous EHM determinations. The kinetic energy or bond order provides a convenient new estimate of ${U}^{\ensuremath{\ast}}$ based on a metallic point at ${V}_{c}(U)$ for $U<{U}^{\ensuremath{\ast}}$. Tuning the BOW phase of half-filled Hubbard models with different intersite potentials indicates a ground state with large charge fluctuations and magnetic frustration. The possibility of physical realizations of a BOW phase is raised for Coulomb interactions.