Bifurcations, stability and mode evolution in segregated quasi-2D condensate mixtures.

We present new features of low energy Bogoliubov quasiparticle excitations of a two-component Bose–Einstein condensate (TBEC) in quasi-2D geometry at zero temperature using Hartree–Fock–Bogoliubov formalism. We, in particular, consider the TBECs of 133Cs–87Rb and 85Rb–87Rb, and show specific features in the low energy excitation spectrum as a function of the interaction strength. For 85Rb–87Rb TBEC, the appearance of a new zero energy mode is observed. Whereas for 133Cs–87Rb TBEC we report a bifurcation of the slosh mode at the point of transition from miscible to immiscible domain. The lower energy mode, after the bifurcation, goes soft and becomes a new Nambu–Goldstone mode of the system. [ABSTRACT FROM AUTHOR]