Low-dimensional optical chirality in complex potentials

Chirality is a universal feature in nature, as observed in fermion interactions and DNA helicity. Much attention has been given to chiral interactions of light, not only regarding its physical interpretation, but also focusing on intriguing phenomena in the excitation, absorption, refraction, and topological phases. Although recent progress in metamaterials has spurred artificial engineering of chirality, most approaches are founded on the same principle of the mixing of electric and magnetic responses. Here we propose non-magnetic chiral interactions of light based on low-dimensional eigensystems. Exploiting the mixing of amplifying and decaying electric modes in a complex material, the low dimensionality in polarization space having a chiral eigenstate is realized, in contrast to two-dimensional eigensystems in previous approaches. The existence of an optical-spin black hole from low-dimensional chirality is predicted, and singular interactions between chiral waves are confirmed experimentally in parity-time-symmetricmetamaterials.