In the context of Gross-Pitaevskii theory, we investigate the unconventional Bose-Einstein condensations in the two-species mixture with
p-wave symmetry in the second band of a bipartite optical lattice. An imaginary-time propagation method is developed to numerically determine the
p-orbital condensation. Different from the single-species case, the two-species boson mixture exhibits two nonequivalent complex condensates in the intraspecies-interaction-dominating regime, exhibiting the vortex-antivortex lattice configuration in the charge and spin channels, respectively. When the interspecies interaction is tuned across the SU(2) invariant point, the system undergoes a quantum phase transition toward a checkerboardlike spin-density wave state with a real-valued condensate wave function. The influence of lattice asymmetry on the quantum phase transition is addressed. Finally, we present a phase-sensitive measurement scheme for experimentally detecting the unconventional Bose-Einstein condensation in our model.
We investigate the formation of discrete breathers (DBs) and the dynamics of the mixture of two-species Bose-Einstein condensates (BECs) in open boundary optical lattices using the discrete nonlinear Schrödinger equations. The results show that the coupling of intra- and interspecies interaction can lead to the existence of pure single-species DBs and symbiotic DBs (i.e., two-species DBs). Furthermore, we find that there is a selective distillation phenomenon in the dynamics of the mixture of two-species BECs. One can selectively distil one species from the mixture of two-species BECs and can even control dominant species fraction by adjusting the intra- and interspecies interaction in optical lattices. Our selective distillation mechanism may find potential application in quantum information storage and quantum information processing based on multi-species atoms.
We give an overview on our current experiments with Bose-Fermi degenerate mixtures in a one dimensional (ID) optical lattice. Our system consists of a Fermi gas of 40 K atoms and a Bose-Einstein condensate of 87 Rb. The two species are simultaneously trapped in a combined magnetic and optical lattice potential. We have investigated the thermodynamical properties of the mixture in a tight lattice and observed a change in the density of states. This is a signature of a quasi two dimensional confinement of the atoms in the lattice sites. We also discuss the mechanical stability of the mixture in presence of the 1D lattice.