  A new model describing the dark sector of the universe is established. The
model involves Bose-Einstein condensate (BEC) as dark energy (DE) and an
excited state above it as dark matter (DM). The condensate is assumed to have a
negative pressure and is embodied as an exotic fluid with Chaplygin equation of
state. Excitations are described as a quasiparticle gas. It is shown that the
model is not in disagreement with the current observations of the cosmic
acceleration. The model predicts increase of the effective cosmological
constant and a complete disappearance of the matter at the far future.
