Topological Behavior Spotted in Photonic Systems

Because of unusual electronic band structures, some materials, such as graphene, can give rise to topological states of matter—exotic quantum states impervious to impurities and lattice deformations. This robustness makes these materials promising components of future quantum information devices, but it is difficult to manipulate the electrons to consistently produce topological states. Consequently, researchers have turned to photonic materials, such as silicon and other semiconductors, where topological states arise from the band structure of quasiparticles that are more easily tamed. Now, two independent groups have engineered two types of photonic materials to observe new topological phases and related behavior.