title: Photonic topological insulators.
abstract: Recent progress in understanding the topological properties of condensed matter has led to the discovery of time-reversal-invariant topological insulators. A remarkable and useful property of these materials is that they support unidirectional spin-polarized propagation at their surfaces. Unfortunately topological insulators are rare among solid-state materials. Using suitably designed electromagnetic media (metamaterials) we theoretically demonstrate a photonic analogue of a topological insulator. We show that metacrystals-superlattices of metamaterials with judiciously designed properties-provide a platform for designing topologically non-trivial photonic states, similar to those that have been identified for condensed-matter topological insulators. The interfaces of the metacrystals support helical edge states that exhibit spin-polarized one-way propagation of photons, robust against disorder. Our results demonstrate the possibility of attaining one-way photon transport without application of external magnetic fields or breaking of time-reversal symmetry. Such spin-polarized one-way transport enables exotic spin-cloaked photon sources that do not obscure each other.
authors.affiliation: Department of Physics, The University of Texas at Austin, Austin, Texas 78712, USA. khanikaev@physics.utexas.edu
authors.forename: Alexander B
authors.initials: AB
authors.lastname: Khanikaev
authors.forename: S Hossein
authors.initials: SH
authors.lastname: Mousavi
authors.forename: Wang-Kong
authors.initials: WK
authors.lastname: Tse
authors.forename: Mehdi
authors.initials: M
authors.lastname: Kargarian
authors.forename: Allan H
authors.initials: AH
authors.lastname: MacDonald
authors.forename: Gennady
authors.initials: G
authors.lastname: Shvets