It is known that the surface of a three-dimensional topological insulator (3D TI) supports a chiral Majorana edge mode at the interface between a superconductor and a magnetic insulator. The complexity of the materials combination is such that this state has not yet been observed. Here we show that a helical Majorana edge mode appears even in the absence of the magnetic insulator, if the Fermi level of the massless surface electrons is at the Dirac point. Specular Andreev reflection of Dirac fermions is at the origin of the effect. The simplified geometry may favor experimental observation of the helical Majorana mode, although it lacks the topological protection of its chiral counterpart.

中文翻译：

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由镜面 Andreev 反射启用的穷人的 Majorana 边缘模式


众所周知，三维拓扑绝缘体 （3D TI） 的表面在超导体和磁绝缘体之间的界面处支持手性马约拉纳边缘模式。材料组合的复杂性是这样的，以至于还没有观察到这种状态。在这里，我们表明，如果无质量表面电子的费米能级位于狄拉克点，即使没有磁绝缘体，也会出现螺旋马约拉纳边缘模式。狄拉克费米子的镜面安德烈耶夫反射是该效应的来源。简化的几何结构可能有利于对螺旋 Majorana 模式的实验观察，尽管它缺乏其手性对应物的拓扑保护。