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Authors: Wenlong Gao, Biao Yang, Mark Lawrence, Fengzhou Fang, Benjamin Béri (School of Physics and Astronomy) & Shuang Zhang (School of Physics and Astronomy)

Unlike Dirac fermions such as electrons, Weyl particles are elusive relativistic fermionic particles with vanishing mass. It had been believed that neutrinos were Weyl fermions until the discovery of neutrino oscillation and mass.  While not having been found as an elementary particle, Weyl particles are present in solid-state materials in the form of quasi-particles.

In this work we discover the presence of a novel type of photonic Weyl 'point' in a naturally existing continuous medium—magnetized plasma. Interestingly, the photonic Weyl point serves as a monopole in momentum space, leading to many intriguing phenomena such as topologically protected surface waves that are immune from scattering by defects. Our study introduces Weyl physics into homogeneous photonic media, which could pave the way for realizing new topological photonic devices.