Demixing effects in mixtures of two bosonic species

Abstract

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 simulations by a two-worm algorithm. The mixture is trapped in a square lattice at different filling conditions. Various quantum phases are stabilized depending on the interplay between intra- and interspecies interactions and on the filling factors. We show that the ground-state phase diagram at half-filling features a demixed superfluid phase and a demixed Mott-insulator phase when the interspecies interaction becomes greater than the intraspecies repulsion, and a double-superfluid phase or a supercounterflow otherwise. We 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. We also study how demixing effects depend on the filling factor of the two components. Finally, we find that the supercounterflow phase is preserved in the presence of unbalanced populations.