Abstract
Recently, it has become apparent that when the interactions between polar molecules in optical lattices become strong, the conventional description using the extended Hubbard model has to be modified by additional terms, in particular a density-dependent tunneling term. We investigate here the influence of this term on the ground-state phase diagrams of the two-dimensional extended Bose–Hubbard model. Using quantum Monte Carlo simulations, we investigate the changes of the superfluid, supersolid and phase-separated parameter regions in the phase diagram of the system. By studying the interplay of the density-dependent hopping with the usual on-site interaction U and nearest-neighbor repulsion V , we show that the ground-state phase diagrams differ significantly from those expected from the standard extended Bose–Hubbard model.
Highlights
In the last decade, the physics of ultra-cold atoms in optical-lattice potentials has undergone extensive developments due to the extreme controllability and versality of the realizable many-body systems
As we have seen in the previous section, the phase diagram of the extended Bose-Hubbard model (EBHM) at vanishing T displays a large variety of phases: Mott insulator (MI), charge density wave (CDW), SF, and supersolid phase (SS)
We have studied the extended Bose–Hubbard model on a square lattice with additional terms coming from density-dependent tunnelings
Summary
The physics of ultra-cold atoms in optical-lattice potentials has undergone extensive developments due to the extreme controllability and versality of the realizable many-body systems (for recent reviews see [1, 2]). It has been realized that even in the simpler case of contact s-wave interactions, in certain parameter regimes, carefully performed tight-binding approximations lead to an additional correlated tunneling term in the resulting microscopic description This term, known in the case of fermions as bond-charge contribution [12], is even more important for bosons [13, 14, 15]. One may expect that similar bond-charge (or density-dependent tunneling) effects may play a important role in the presence of dipolar interactions This assumption has been verified by some of us [20] in a recent study, where it has been shown that the additional terms in the Hamiltonian may destroy some insulating phases and can create novel pair-superfluid states. In the present model, the sign of the additional tunneling (or, more precisely, the relative sign between the standard tunneling and the densitydependent one) can stabilize or destabilize the supersolid phases
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