How Chern-Simons surfaces trap one-handed light waves

Chern-Simons interfaces (a thin layer in flat space with a particular quantum interaction) act as a one-way mirror for light: they let left-handed photons and right-handed photons behave completely differently. The authors solved the full wave equations and found one gapless, chiral surface photon mode—a type of light bound to the interface with linear frequency dependence and peculiar optical properties. This reveals how even simple quantum interactions can engineer exotic light behavior without relying on bulk materials or resonator tricks.