Photonic Dirac Nodal Line Semimetals Realized by Hyper-crystal

TL;DR

This paper introduces a new type of photonic Dirac nodal line semimetal using hyperbolic metamaterials in one-dimensional photonic crystals, enabling flexible control and exploration of topological photonic states.

Contribution

The authors design hyper-crystals with photonic Dirac nodal line semimetals, demonstrating a novel platform for topological photonics using hyperbolic dispersion and polarization control.

Findings

Realization of photonic Dirac nodal line semimetals in hyper-crystals.

Control of photonic DNLSs via phase compensation and hyperbolic dispersion.

Potential to explore Dirac/Weyl physics in classical wave systems.

Abstract

Recently, the gapless Dirac/Weyl nodal semimetals with linear dispersion and topologically protected modes degeneracy are rapidly growing frontiers of topological physics. Especially, type-I, type-II, and critical type-III nodal semimetals are discovered according to the tilt angles of the Dirac/Weyl cones. Here, by introducing hyperbolic metamaterials into one-dimensional photonic crystals, we design the "hyper-crystal" and study the photonic four-fold degenerate Dirac nodal line semimetals (DNLSs) with two types of perpendicularly polarized waves. Moreover, the flexibly controlled photonic DNLSs using the phase compensation effect of hyperbolic dispersion are studied. Our results not only demonstrate a new platform to realize the various photonic DNLSs, where the optical polarization plays the role of electron spin in electronic DNLSs, but also may pave a novel way to explore the abundant Dirac/Weyl physics in the simple classical wave systems.