Topological quantum properties of chiral crystals
Topological quantum properties of chiral crystals
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DOI：
10.1038/s41563-018-0169-3
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发表时间：
2018-11-01
期刊：
影响因子：
41.2
通讯作者：
Hasan, M. Zahid
中科院分区：
文献类型：
--
作者：
Chang, Guoqing;Wieder, Benjamin J.;Hasan, M. Zahid
手性晶体是具有晶格结构的材料，由于缺乏反转、镜像或其他旋转反转对称性，该晶格结构具有明确的手性。虽然它已被证明，晶体对称性的存在下，可以保护拓扑带交叉，手性晶体的拓扑电子性质仍然在很大程度上未被表征。在这里，我们表明，Kramers-Weyl费米子是一个普遍的拓扑电子性质的所有非磁性手征晶体的自旋轨道耦合，并保证了结构的手征性，晶格平移和时间反演对称性。与传统的外尔费米子不同，它们以时间反演不变的动量出现。在65个手性空间群中的33个中，我们确定了具有代表性的手性材料，其中Kramers-Weyl费米子与低能物理有关。我们确定，所有的点状节点简并在非磁性手性晶体与相关的自旋轨道耦合进行非平凡的陈数。Kramers-Weyl材料可以在一个非常大的能量窗口上表现出类似于电子自旋织构和拓扑非平凡的体费米表面。
Chiral crystals are materials with a lattice structure that has a well-defined handedness due to the lack of inversion, mirror or other roto-inversion symmetries. Although it has been shown that the presence of crystalline symmetries can protect topological band crossings, the topological electronic properties of chiral crystals remain largely uncharacterized. Here we show that Kramers-Weyl fermions are a universal topological electronic property of all non-magnetic chiral crystals with spin-orbit coupling and are guaranteed by structural chirality, lattice translation and time-reversal symmetry. Unlike conventional Weyl fermions, they appear at time-reversal-invariant momenta. We identify representative chiral materials in 33 of the 65 chiral space groups in which Kramers-Weyl fermions are relevant to the low-energy physics. We determine that all point-like nodal degeneracies in non-magnetic chiral crystals with relevant spin-orbit coupling carry non-trivial Chern numbers. Kramers-Weyl materials can exhibit a monopole-like electron spin texture and topologically non-trivial bulk Fermi surfaces over an unusually large energy window.