Three dimensional photonic Dirac points in metamaterials

TL;DR

This paper theoretically demonstrates the realization of three-dimensional photonic Dirac points in metamaterials, revealing topologically protected surface states and their implications for diffraction-less light propagation and fundamental physics.

Contribution

It introduces a novel theoretical framework for achieving photonic Dirac points in metamaterials through electromagnetic duality, expanding topological photonics beyond photonic crystals.

Findings

Observation of spin polarized Fermi arc like surface states

Decomposition of Dirac points into Weyl points upon reflection

Topological link between Dirac points and vortex/vector beams

Abstract

Topological semimetals, representing a new topological phase that lacks a full bandgap in bulk states and exhibiting nontrivial topological orders, recently have been extended to photonic systems, predominantly in photonic crystals and to a lesser extent, metamaterials. Photonic crystal realizations of Dirac degeneracies are protected by various space symmetries, where Bloch modes span the spin and orbital subspaces. Here, we theoretically show that Dirac points can also be realized in effective media through the intrinsic degrees of freedom in electromagnetism under electromagnetic duality. A pair of spin polarized Fermi arc like surface states is observed at the interface between air and the Dirac metamaterials. These surface states show linear k-space dispersion relation, resulting in nearly diffraction-less propagation. Furthermore, eigen reflection fields show the decomposition from a Dirac point to two Weyl points. We also find the topological correlation between a Dirac point and vortex/vector beams in classic photonics. The theoretical proposal of photonic Dirac point lays foundation for unveiling the connection between intrinsic physics and global topology in electromagnetism.