Mott insulator phases of nonlocally coupled bosons in bilayer optical superlattices

Abstract

We investigate the ground state properties of a non-locally coupled bosonic system in a bilayer optical superlattice by considering bosons in one layer to be of softcore in nature and separately allowing two and three body hardcore constraints on the other layer. We find that the presence of different constraints on bosons in one layer influences the overall phase diagram exhibiting various Mott insulator phases at incommensurate densities due to the presence of the superlattice potential apart from the usual Mott insulators at commensurate densities. Moreover, the presence of two or three-body constraints significantly modifies the Mott insulator-Superfluid phase transition points as a function of the superlattice potential. Due to the various competing interactions, constraints and superlattice potential the phase diagrams exhibit significantly different features. We obtain the complete phase diagrams by using the cluster-mean-field theory approach. We further extend this work to a coupled two-leg ladder superlattice where we obtain similar physics using the density matrix renormalization group method .