Abstract
An odd number of gapless Dirac fermions is guaranteed to exist at a surface of a strong topological insulator. We show that in a thin-film geometry and under external bias, electron-hole pairs that reside in these surface states can condense to form a novel exotic quantum state which we propose to call “topological exciton condensate” (TEC). This TEC is similar in general terms to the exciton condensate recently argued to exist in a biased graphene bilayer, but with different topological properties. It exhibits a host of unusual properties including a stable zero mode and a fractional charge carried by a singly quantized vortex in the TEC order parameter.
- Received 10 February 2009
DOI:https://doi.org/10.1103/PhysRevLett.103.066402
©2009 American Physical Society