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

preprint

posted on 2023-01-11, 23:06 authored by Christina Jörg, Sachin Vaidya, Jiho Noh, Alexander Cerjan, Shyam Augustine, Georg von Freymann, Mikael C. RechtsmanWeyl 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.