Department of Physics, The University of Texas at Austin, Austin, Texas 78712, USA.
Nat Mater. 2013 Mar;12(3):233-9. doi: 10.1038/nmat3520. Epub 2012 Dec 16.
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.
近年来，人们对凝聚态物质拓扑性质的理解取得了进展，进而发现了时间反演不变的拓扑绝缘体。这些材料的一个显著而有用的特性是，它们在表面支持单向自旋极化传播。不幸的是，拓扑绝缘体在固态材料中很少见。我们使用适当设计的电磁介质（超材料），从理论上演示了拓扑绝缘体的光子类似物。我们表明，金属-晶体——具有精心设计特性的超材料的超晶格——为设计拓扑非平凡的光子态提供了一个平台，类似于已经为凝聚态拓扑绝缘体确定的那些光子态。金属-晶体的界面支持螺旋边缘态，其表现出对光子的自旋极化单向传播，对无序具有鲁棒性。我们的结果表明，在不施加外磁场或破坏时间反演对称性的情况下，实现单向光子输运是可能的。这种自旋极化的单向传输使得能够实现奇特的自旋伪装光子源，而不会相互掩盖。
