Abstract
Three-dimensional topological insulators have protected Dirac-cone surface states. In this Letter we argue that gapped excitonic superfluids with spontaneous coherence between top and bottom surfaces can occur in the topological insulator (TI)-thin-film quantum Hall regime. We find that the large dielectric constants of TI materials increase the layer separation range over which coherence survives and decrease the superfluid sound velocity, but have little influence on the superfluid density or on the charge gap. The coherent state at total Landau-level filling factor is predicted to be free of edge modes, qualitatively altering its transport phenomenology compared to the widely studied case of in GaAs double-quantum wells.
- Received 19 July 2011
DOI:https://doi.org/10.1103/PhysRevLett.107.246401
© 2011 American Physical Society