# Bose-Einstein condensation of quasiparticles in graphene

## TL;DR

This paper predicts Bose-Einstein condensation and superfluidity of quasiparticles like magnetoexcitons and polaritons in graphene structures under high magnetic fields, highlighting their unique properties and phase transitions.

## Contribution

It introduces theoretical predictions of BEC and superfluidity of various quasiparticles in graphene-based systems, including magnetoexcitons, magnetobiexcitons, and polaritons, under high magnetic fields.

## Key findings

- Predicted BEC and superfluidity of 2D magnetoexcitons in graphene.
- Established stability conditions for magnetobiexcitons in superlattices.
- Calculated critical temperatures for BEC of excitonic polaritons.

## Abstract

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.