Bose-Einstein condensation of quasiparticles in graphene.

The collective properties of different quasiparticles in various graphene-based structures in a high magnetic field have been studied. We predict Bose-Einstein condensation (BEC) and the superfluidity of 2D spatially indirect magnetoexcitons in a 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 a 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 a pair of indirect excitons with antiparallel dipole moments, is considered in a graphene superlattice. The superfluid density and the temperature of the Kosterlitz-Thouless phase transition for magnetobiexcitons in a graphene superlattice are obtained. Moreover, the BEC of excitonic polaritons in a GL embedded in a semiconductor microcavity in a high magnetic field is predicted. While the superfluid phase in this magnetoexciton polariton system is absent due to a vanishing magnetoexciton-magnetoexciton interaction in a single layer in the limit of a high magnetic field, the critical temperature of the BEC formation is calculated. The observation of the BEC and superfluidity of 2D quasiparticles in graphene in a high magnetic field would be interesting confirmation of the phenomena we have described.