Demixing Effects in Mixtures of Two Bosonic Species

Motivated by recent experiments on two-component systems, we investigate the ground-state phase diagram of a mixture of two bosonic species by means of path-integral quantum Monte Carlo by the two-worm algorithm. The mixture is trapped in a square lattice at half-filling conditions. Various quantum phases are stabilized depending on the interplay between intra- and inter-species interactions. We show that the phase diagram features a demixed superfluid phase and demixed Mott-Insulator phase when the inter-species interaction becomes greater than the intra-species repulsion, and a double-superfluid phase or a supercounterflow otherwise. We also show that demixing, characterized by spatial separation of the two species, can be detected experimentally through the effects of anisotropy revealed by time-of-flight images.