Quantum phase transitions in attractive extended Bose-Hubbard Model with three-body constraint

TL;DR

This paper investigates how nearest-neighbor repulsion influences the phase diagram of an attractive Bose-Hubbard model with three-body constraints, revealing new phases and transition behaviors relevant for ultracold gases.

Contribution

It introduces the effects of repulsion on phase transitions and stability of dimer superfluid phases in an extended Bose-Hubbard model with three-body constraints.

Findings

Dimer checkerboard solid state appears at unit filling.

First-order transitions can become continuous with increased repulsion.

Dimer superfluid stability is enhanced by tuning repulsion.

Abstract

The effect of nearest-neighbor repulsion on the ground-state phase diagrams of three-body constrained attractive Bose lattice gases is explored numerically. When the repulsion is turned on, in addition to the uniform Mott insulating state and two superfluid phases (the atomic and the dimer superfluids), a dimer checkerboard solid state appears at unit filling, where boson pairs form a solid with checkerboard structure. We find also that the first-order transitions between the uniform Mott insulating state and the atomic superfluid state can be turned into the continuous ones as the repulsion is increased. Moreover, the stability regions of the dimer superfluid phase can be extended to modest values of the hopping parameter by tuning the strength of the repulsion. Our conclusions hence shed light on the search of the dimer superfluid phase in real ultracold Bose gases in optical lattices.