  The collective properties of different quasiparticles in various graphene
based structures in high magnetic field have been studied. We predict
Bose-Einstein condensation (BEC) and superfluidity of 2D spatially indirect
magnetoexcitons in two-layer graphene. The superfluid density and the
temperature of the Kosterlitz-Thouless phase transition are shown to be
increasing functions of the excitonic density but decreasing functions of
magnetic field and the interlayer separation. The instability of the ground
state of the interacting 2D indirect magnetoexcitons in a slab of superlattice
with alternating electron and hole graphene layers (GLs) is established. The
stable system of indirect 2D magnetobiexcitons, consisting of pair of indirect
excitons with opposite dipole moments, is considered in graphene superlattice.
The superfluid density and the temperature of the Kosterlitz-Thouless phase
transition for magnetobiexcitons in graphene superlattice are obtained.
Besides, the BEC of excitonic polaritons in GL embedded in a semiconductor
microcavity in high magnetic field is predicted. While superfluid phase in this
magnetoexciton polariton system is absent due to vanishing of
magnetoexciton-magnetoexciton interaction in a single layer in the limit of
high magnetic field, the critical temperature of BEC formation is calculated.
The essential property of magnetoexcitonic systems based on graphene (in
contrast, e.g., to a quantum well) is stronger influence of magnetic field and
weaker influence of disorder. Observation of the BEC and superfluidity of 2D
quasiparticles in graphene in high magnetic field would be interesting
confirmation of the phenomena we have described.
