Discovery of a maximally charged Weyl point

Qiaolu Chen; Fujia Chen; Qinghui Yan; Li Zhang; Zhen Gao; Shengyuan A. Yang; Zhi-Ming Yu; Hongsheng Chen; Baile Zhang; Yihao Yang

doi:10.1038/s41467-022-34978-z

arXiv · 2203.10722

Discovery of a maximally charged Weyl point

Qiaolu Chen·Fujia Chen·Qinghui Yan·Li Zhang·Zhen Gao·Shengyuan A. Yang·Zhi-Ming Yu·Hongsheng Chen·Baile Zhang·Yihao Yang

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Abstract

The hypothetical Weyl particles in high-energy physics have been discovered in three-dimensional crystals as collective quasiparticle excitations near two-fold degenerate Weyl points. Such momentum-space Weyl particles carry quantized chiral charges, which can be measured by counting the number of Fermi arcs emanating from the corresponding Weyl points. It is known that merging unit-charged Weyl particles can create new ones with more charges. However, only very recently has it been realised that there is an upper limit - the maximal charge number that a two-fold Weyl point can host is four - achievable only in crystals without spin-orbit coupling. Here, we report the experimental realisation of such a maximally charged Weyl point in a three-dimensional photonic crystal. The four charges support quadruple-helicoid Fermi arcs, forming an unprecedented topology of two non-contractible loops in the surface Brillouin zone. The helicoid Fermi arcs also exhibit the long-pursued type-II van Hove singularities that can reside at arbitrary momenta. This discovery reveals a type of maximally charged Weyl particles beyond conventional topological particles in crystals.

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Qiaolu Chen, Fujia Chen, Qinghui Yan, Li Zhang, Zhen Gao, Shengyuan A. Yang, Zhi-Ming Yu, Hongsheng Chen, Baile Zhang, Yihao Yang. 2022-03-21. Discovery of a maximally charged Weyl point. https://doi.org/10.1038/s41467-022-34978-z

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