Miscibility-immiscibility transition of strongly interacting bosonic mixtures in optical lattices

Abstract

Interaction plays key role in the mixing properties of a multi-component system. The miscibility-immiscibility transition (MIT) in a weakly interacting mixture of Bose gases is predominantly determined by the strengths of the intra and inter-component two-body contact interactions. On the other hand, in the strongly interacting regime interaction induced processes become relevant. Despite previous studies on bosonic mixtures in optical lattices, the effects of the interaction induced processes on the MIT remains unexplored. In this work, we investigate the MIT in the strongly interacting phases of two-component bosonic mixture trapped in a homogeneous two-dimensional square optical lattice. Particularly we examine the transition when both the components are in superfluid (SF), one-body staggered superfluid (OSSF) or supersolid (SS) phases. Our study prevails that, similar to the contact interactions, the MIT can be influenced by competing intra and inter-component density induced tunnelings and off-site interactions. To probe the MIT in the strongly interacting regime, we study the extended version of the Bose-Hubbard model with the density induced tunneling and nearest-neighbouring interaction terms, and focus in the regime where the hopping processes are considerably weaker than the on-site interaction. We solve this model through site-decoupling mean-field theory with Gutzwiller ansatz and characterize the miscibility through the site-wise co-existence of the two-component across the lattice. Our study contributes to the better understanding of miscibility properties of multi-component systems in the strongly interacting regime.