Chiral Electromagnetic Surface Waves on Chern-Simons Interfaces

TL;DR

The paper demonstrates that Maxwell theory with a Chern-Simons interface supports a unique, gapless, chiral electromagnetic surface wave with linear dispersion, arising purely from topological effects without material or geometric confinement.

Contribution

It provides an exact solution showing how Chern-Simons interactions induce chiral surface electromagnetic modes in vacuum electrodynamics.

Findings

Supports a localized, normalizable chiral surface photon mode.

The mode has a linear dispersion relation.

The mode's index of refraction is determined solely by the Chern-Simons coefficient.

Abstract

We show that Maxwell theory with a codimension-$1$ Chern-Simons interface supports chiral electromagnetic surface waves on the interface, even when the bulk theory on both sides is conventional vacuum electrodynamics in infinite space. Solving the exact boundary value problem we find that the Chern-Simons interaction acts with opposite sign on the two helicities oriented along the interface, giving rise to one normalizable mode localized on the interface. This mode is a gapless chiral surface photon with linear dispersion and a frequency-independent index of refraction set by the Chern-Simons coefficient. This mode exists despite the absence of ambient material response or geometric confinement.