Path-integral quantum Monte Carlo study of a mixture of Bose–Einstein condensates

Two-species hard-core bosons trapped in a three-dimensional isotropic harmonic potential at finite temperature are studied with the path-integral quantum Monte Carlo simulation. The double condensates show two distinct structures depending on how the external potentials are set. We find that the heavier particles form an outer shell with an identical external potential for both species, whereas the lighter particles form an outer shell with the same trapping frequency. Phase separation is observed in both the spatial and energy spaces. We provide physical interpretations of these phenomena and suggest future experiment to confirm these findings.