Double-well Bose-Hubbard model with nearest-neighbor and cavity-mediated long-range interactions

We consider a one-dimensional Bose-Hubbard model (BHM) with on-site double-well potentials and study the effect of nearest-neighbor repulsion and cavity-mediated long-range interactions by calculating the ground-state phase diagrams with quantum Monte Carlo simulations. We show that when the intrawell repulsion is as strong as the on-site repulsion, a dimerized Mott-insulator phase appears at the tip of the dimerized density-wave phase for a density of one particle per double well. Furthermore, we find a dimerized Haldane-insulator phase in the double-well BHM with nearest-neighbor interaction, which is identical to a dimerized BHM with repulsive interactions up to the third neighbor.