Photonic Analogue of Two-dimensional Topological Insulators and Helical   One-Way Edge Transport in Bi-Anisotropic Metamaterials
  Recent progress in understanding the topological properties of condensed matter has led to the discovery of time-reversal invariant topological insulators. Because of limitations imposed by nature, topologically non-trivial electronic order seems to be uncommon except in small-band-gap semiconductors with strong spin-orbit interactions. In this Article we show that artificial electromagnetic structures, known as metamaterials, provide an attractive platform for designing photonic analogues of topological insulators. We demonstrate that a judicious choice of the metamaterial parameters can create photonic phases that support a pair of helical edge states, and that these edge states enable one-way photonic transport that is robust against disorder. 
Alexander B. Khanikaev, S. Hossein Mousavi, Wang-Kong Tse, Mehdi   Kargarian, Allan H. MacDonald, and Gennady Shvets
cond-mat.mtrl-sci cond-mat.str-el physics.optics