The exciton condensate in bilayer systems

Quasi two-dimensional electron systems in the quantum Hall (QH) regime have been continuously revealing a wide variety of new phenomena that arise from electron-electron interactions [1]. In particular, bilayer system, consisting of two layers separated by a narrow barrier, involves tremendously rich physics as the lowest Landau level in every layer is half filled with electrons, so that the total filling factor is (( = 1. This system is equivalent to two interacting electron-hole layers, where the barrier between them inhibits electron-hole annihilation, thereby promoting exciton formation. As several investigations in the last years have shown, these systems are highly favorable for the investigation of exciton condensation. Recently, some reports have point to graphene-based structures as the new candidate for the realization of bilayer exciton condensate [2]. Due to its particular Dirac-like band structure, the electron-hole symmetry of graphene results in a perfect nesting between the electron and holes in different layers, and contrary to the case of conventional GaAs bilayers, presents the ideal conditions for exciton condensation without the need of an external magnetic field. More over, it was claimed that even room temperature superfluidity could be achieved, what makes this systems 1 Paula Giudici technologically highly interesting. The goal of this project is the investigation of the exciton condensate in GaAs and graphene-based bilayer structures, in the later case with and without an external magnetic field.