Fermi Arc Criterion for Surface Majorana Modes in Superconducting Time-Reversal Symmetric Weyl Semimetals
Fermi Arc Criterion for Surface Majorana Modes in Superconducting Time-Reversal Symmetric Weyl Semimetals
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DOI：
10.1103/physrevlett.127.187002
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发表时间：
2021-10-26
影响因子：
8.6
通讯作者：
Hosur, Pavan
中科院分区：
文献类型：
--
作者：
Giwa, Rauf;Hosur, Pavan
通过利用金属和绝缘体中的超导性和能带拓扑之间的相互作用，人们发现了许多通往马约拉纳费米子的巧妙途径。然而，半金属的实现仍然较少探索。我们问，“在什么条件下，时间反演对称的外尔半金属（仅具有时间反演对称性的三维半金属）中的超导涡旋会在表面捕获马约拉纳费米子？”如果每个常数 k(z) 平面（其中 z 是涡旋轴）包含相同数量的每个手性的 Weyl 节点，我们可以预测一个一般有间隙的涡旋，并根据费米弧结构得出拓扑不变量 nu = +/- 1，该结构表示表面马约拉纳费米子的存在或不存在。相反，如果某些常数 k(z) 平面包含 Weyl 节点的净手性，则涡流是无间隙的。我们在微扰方案中分析计算 nu 并通过晶格模型提供数值支持。该标准在存在其他体积和表面带的情况下仍然存在，并在倾斜涡旋时产生平凡、无间隙和拓扑涡旋之间的相变。我们提出具有破缺反演对称性的 Li(Fe0.91Co0.09)As 和 Fe1+ySe0.45Te0.55 作为实现我们建议的候选者。
Many clever routes to Majorana fermions have been discovered by exploiting the interplay between superconductivity and band topology in metals and insulators. However, realizations in semimetals remain less explored. We ask, "Under what conditions do superconductor vortices in time-reversal symmetric Weyl semimetals-three-dimensional semimetals with only time-reversal symmetry-trap Majorana fermions on the surface?" If each constant-k(z) plane, where z is the vortex axis, contains equal numbers of Weyl nodes of each chirality, we predict a generically gapped vortex and derive a topological invariant nu = +/- 1 in terms of the Fermi arc structure that signals the presence or absence of surface Majorana fermions. In contrast, if certain constant-k(z) planes contain a net chirality of Weyl nodes, the vortex is gapless. We analytically calculate nu within a perturbative scheme and provide numerical support with a lattice model. The criteria survive the presence of other bulk and surface bands and yield phase transitions between trivial, gapless, and topological vortices upon tilting the vortex. We propose Li(Fe0.91Co0.09)As and Fe1+ySe0.45Te0.55 with broken inversion symmetry as candidates for realizing our proposals.