Electron-hole pairing in topological insulator heterostructures in the quantum Hall state

A thin film of a topological insulator (TI) on a dielectric substrate and a bulk TI-dielectric film-bulk TI structure are considered as natural double-well heterostructures suitable for realizing the counterflow superconductivity. The effect is connected with pairing of electrons and holes belonging to different surfaces of TI and the transition of a gas of electron-hole pairs into a superfluid state. The case of TI heterostructures subjected to a strong perpendicular magnetic field is considered. It is shown that such systems are characterized by two critical temperatures-a mean-field temperature of pairing and a much smaller temperature of the superfluid transition. The dependence of the critical temperatures on the magnetic field is computed. The advantages of TI based structures in comparison with GaAs heterostructures as well as graphene based heterostructures are discussed.