Near-zero index magneto-optical medium realized with an unpaired Dirac point

TL;DR

This paper demonstrates a gyromagnetic photonic crystal with an unpaired Dirac cone at the Brillouin zone center, enabling near-zero index and topologically protected edge states in magneto-optical media.

Contribution

It introduces a novel unpaired Dirac cone in a gyromagnetic photonic crystal with broken symmetries, linking topological edge states to surface waves in magneto-optical materials.

Findings

Realization of an unpaired Dirac cone at the Brillouin zone center.

Observation of unidirectional edge states along domain walls.

Effective medium model with near-zero refractive index and Voigt parameter near unity.

Abstract

We realize an unpaired Dirac cone at the center of the first Brillouin zone, using a gyromagnetic photonic crystal with broken square sub-lattice symmetry and broken time reversal symmetry. The behavior of the Dirac modes can be described by a gyromagnetic effective medium model with near-zero refractive index, and Voigt parameter near unity. When two domains are subjected to opposite magnetic biases, there exist unidirectional edge states along the domain wall. This establishes a link between topological edge states and the surface waves of homogenous magneto-optical media.