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Discovery of a maximally charged Weyl point
Nature Communications ( IF 16.6 ) Pub Date : 2022-11-30 , DOI: 10.1038/s41467-022-34978-z
Qiaolu Chen 1, 2, 3 , Fujia Chen 1, 2, 3 , Yuang Pan 1, 2, 3 , Chaoxi Cui 4, 5 , Qinghui Yan 1, 2, 3 , Li Zhang 1, 2, 3 , Zhen Gao 6 , Shengyuan A Yang 7 , Zhi-Ming Yu 4, 5 , Hongsheng Chen 1, 2, 3 , Baile Zhang 8, 9 , Yihao Yang 1, 2, 3
Affiliation  

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 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.



中文翻译:

最大电荷外尔点的发现

高能物理学中假设的 Weyl 粒子已在三维晶体中被发现为两倍简并 Weyl 点附近的集体准粒子激发。这种动量空间 Weyl 粒子携带量化的手性电荷,可以通过计算从相应的 Weyl 点发出的费米弧的数量来测量。众所周知,合并带单位电荷的 Weyl 粒子可以产生带更多电荷的新粒子。然而,直到最近人们才意识到存在一个上限——两倍外尔点可以容纳的最大电荷数是四个——只能在没有自旋轨道耦合的晶体中实现。在这里,我们报告了三维光子晶体中这种带最大电荷的外尔点的实验实现。四个电荷支持四螺旋费米弧,在表面布里渊区形成两个不可收缩环的前所未有的拓扑结构。螺旋费米弧还展示了长期追求的 II 型范霍夫奇点,它可以存在于任意动量。这一发现揭示了晶体中一种超越常规拓扑粒子的最大带电外尔粒子。

更新日期:2022-11-30
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