三维Nexus三相点退化的拓扑特征
On the topological character of three-dimensional Nexus triple point degeneracies
摘要：
最近一类三维能带结构被确定，主机两个折叠线简并满足三重或三相点简并，抵制通常的拓扑特征的孤立点简并在狄拉克/外尔半金属。对于这些所谓的“Nexus”费米子，它位于狄拉克/外尔费米子之外，我们提出了几个概念来描述波函数几何并阐明其拓扑结构。我们的方法是基于我们最近研究的一个二维模拟的Nexus波函数的解析性质的理解。我们用它来写一个同源分类的各种Nexus三相点退化的三维空间。
英文摘要：
Recently a generic class of three-dimensional band structures was identified that host two-fold line degeneracies meeting at three-fold or triple point degeneracies, which resist the usual topological characterization of isolated point degeneracies as in Dirac/Weyl semimetals. For these so-called ``Nexus" fermions which lie beyond Dirac/Weyl fermions, we lay out several concepts to characterize the wavefunction geometry and spell out its topology. Our approach is based on an understanding of the analyticity properties of Nexus wavefunctions building on a two-dimensional analogue studied recently by us. We use this to write down a homological classification of various Nexus triple point degeneracies in three dimensions.
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