Weyl半金属的高阶拓扑超导体
Higher-order topological superconductors from Weyl semimetals
摘要：
我们建议，掺杂的Weyl半金属与四个Weyl点是自然的候选人，以实现高阶拓扑超导体，表现出完全带隙的体积，而表面主机强大的无带隙手性铰链状态。我们发现，在这样一个掺杂的外尔半金属，一个无特征的有限范围的吸引相互作用有利于$p+ip$配对对称性。通过分析它的拓扑性质，我们确定这样的手征配对状态作为一个高阶拓扑超导体，这取决于一个四重旋转反转对称$\mathsf{R}_{4z}$的存在，要么是内在的（这意味着相应的铰链状态只能通过关闭体隙，而不是修改表面状态）或外在的。我们通过最近开发的高阶拓扑结构，包括Wannier可表示性，Wannier谱和缺陷分类方法的各种方法来实现这种理解。对于$\mathsf{R}_{4z}$对称的情况，我们提供了一个完整的分类的高阶拓扑超导体。我们表明，这样的二阶拓扑超导体表现出手征铰链模式，是强大的相互作用的情况下，但可以消除引入表面拓扑秩序的成本。
英文摘要：
We propose that doped Weyl semimetals with four Weyl points are natural candidates to realize higher-order topological superconductors, which exhibit a fully gapped bulk while the surface hosts robust gapless chiral hinge states. We show that in such a doped Weyl semimetal, a featureless finite-range attractive interaction favors a $p+ip$ pairing symmetry. By analyzing its topological properties, we identify such a chiral pairing state as a higher-order topological superconductor, which depending on the existence of a four-fold roto-inversion symmetry $\mathsf{R}_{4z}$, is either intrinsic (meaning that the corresponding hinge states can only be removed by closing the bulk gap, rather than modifying the surface states) or extrinsic. We achieve this understanding via various methods recently developed for higher-order topology, including Wannier representability, Wannier spectrum, and defect classification approaches. For the $\mathsf{R}_{4z}$ symmetric case, we provide a complete classification of the higher-order topological superconductors. We show that such second-order topological superconductors exhibit chiral hinge modes that are robust in the absence of interaction effects but can be eliminated at the cost of introducing surface topological order.
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