Observation of Quadratic (Charge-2) Weyl Point Splitting in Near-Infrared Photonic Crystals

TL;DR

This study experimentally demonstrates the splitting of a charge-2 Weyl point into two charge-1 Weyl points in a 3D photonic crystal, with theoretical analysis and infrared spectrometry confirming the process, advancing topological photonic device development.

Contribution

First experimental observation of charge-2 Weyl point splitting in a 3D photonic crystal with theoretical and spectrometric validation.

Findings

Charge-2 Weyl point splits into two charge-1 Weyl points upon symmetry breaking.

Theoretical analysis predicts Weyl point movement within the Brillouin zone.

Infrared spectrometry confirms the Weyl point splitting experimentally.

Abstract

Weyl points are point degeneracies that occur in momentum space of periodic materials, and are associated with a quantized topological charge. We experimentally observe in a 3D micro-printed photonic crystal that a charge-2 Weyl point can be split into two charge-1 Weyl points as the protecting symmetry of the original charge-2 Weyl point is broken. Moreover, we use a theoretical analysis to confirm where the charge-1 Weyl points move within the Brillouin zone as the strength of the symmetry breaking increases, and confirm it in experiments using Fourier-transform infrared spectrometry. This micro-scale observation and control of Weyl points is important for realizing robust topological devices in the near-infrared.