Discovery of a maximally charged Weyl point

• DOI: 10.1038/s41467-022-34978-z
• Publication Date: 2022-11-30T06:20:45Z
• Authors: Qiaolu Chen; Fujia Chen; Yuang Pan; Chaoxi Cui; Qinghui Yan; Li Zhang; Zhen Gao; Shengyuan A. Yang; Zhi-Ming Yu; Hongsheng Chen; Baile Zhang; Yihao Yang
• Keywords: Condensed Matter - Mesoscale and Nanoscale Physics; Science; Q; FOS: Physical sciences; Hypothesis Testing; 01 natural sciences; Article; :Physics [Science]; Mesoscale and Nanoscale Physics (cond-mat.mes-hall); 0103 physical sciences; Crystal Structure

AbstractThe 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 quantised 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.