  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 excitation, absorption, refraction, and
topological phase. 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
nonmagnetic 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 2-dimensional eigensystems in previous
approaches. The existence of optical spin black hole from low-dimensional
chirality is predicted, and singular interactions between chiral waves are
confirmed experimentally in parity-time-symmetric metamaterials.
