Tuning the bond order wave (BOW) phase of half-filled extended Hubbard models

TL;DR

This study investigates the phase diagram of the one-dimensional half-filled extended Hubbard model, identifying conditions for the bond order wave (BOW) phase and its boundaries using advanced computational methods.

Contribution

It provides new insights into how extended interactions influence the BOW phase and introduces a novel estimate for the critical interaction strength U* based on kinetic energy.

Findings

The BOW phase exists with finite magnetic gap for U < U* near the CDW boundary.

Extended interactions lead to a less cooperative CDW transition and a wider BOW phase.

A new method using kinetic energy estimates U* at the metallic point.

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 $U < U^*$, the critical point, and nearest neighbor interaction $V_c \approx U/2$ 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 $U^*$ and wider BOW phase. Density matrix renormalization group (DMRG) 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 $U^*$ based on a metallic point at $V_c(U)$ for $U < U^*$. 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.