Observation of Three-dimensional Photonic Dirac points and Spin-polarized Surface Arcs

TL;DR

This paper reports the first experimental observation of three-dimensional photonic Dirac points in a metamaterial, revealing spin-polarized surface arcs and advancing the understanding of topological photonic states.

Contribution

It introduces a novel photonic metamaterial that hosts stable 3D Dirac points and demonstrates spin-polarized surface arcs, a first in classical systems.

Findings

Observation of two symmetrically placed Dirac points stabilized by electromagnetic duality symmetry

Demonstration of spin-polarized surface arcs in the photonic system

The system serves as an effective platform for topological photonics research

Abstract

Topological phases arise from the elegant mathematical structures imposed by the interplay between symmetry and topology1-5. From gapped topological insulators to gapless semimetals, topological materials in both quantum and classical systems, have grown rapidly in the last decade. Among them, three-dimensional Dirac semimetal lies at the topological phase transition point between various topological phases. It shares multiple exotic topological features with other topological materials, such as Fermi arcs and chiral anomaly with Weyl semimetals30, spin-dependent surface states with topological insulators29. In spite of the important role it plays in topological physics, no experimental observation of three-dimension Dirac points has been reported in classical systems so far. Here, we experimentally demonstrate three-dimension photonic Dirac points in an elaborately designed photonic metamaterial, in which two symmetrically placed Dirac points are stabilized by electromagnetic duality symmetry31. Spin-polarized surface arcs (counterparts of Fermi arcs in electronic systems) are demonstrated, which paves the way towards spin-multiplexed topological surface wave propagation. Closely linked to other exotic states through topological phase transitions, our system offers an effective medium platform for topological photonics.