量子反常霍尔绝缘体/自旋单态s波超导体混合系统的边缘态理论
Theory of edge states in a quantum anomalous Hall insulator/ spin-singlet s-wave superconductor hybrid system
摘要：
研究了自旋单重态s波超导体与量子反常霍尔系统通过邻近效应耦合后的边缘态，阐明了它们的拓扑性质。当我们考虑QAHS中诱导的超导对势时，出现了具有非零Chern数的拓扑相$i.e.$、${\cal N}=1$和${\cal N}=2$，其中Andreev束缚态表现为手征Majorana边模。我们计算了边缘模的能谱和局域态密度。研究发现，在平行于界面方向施加塞曼磁场或掺杂引起的化学势的移动，可以使${\cal N}=2$的简并手征Majorana边模被抬离。手征Majorana边缘模的简并性及其提升由定义在边缘动量的时间反演不变点处的两个不同的缠绕数来解释。
英文摘要：
We study the edge states for a quantum anomalous Hall system (QAHS) coupled with a spin-singlet s-wave superconductor through the proximity effect, and clarify the topological nature of them. When we consider a superconducting pair potential induced in the QAHS, there appear topological phases with nonzero Chern numbers, $i.e.$, ${\cal N}=1$ and ${\cal N}=2$, where Andreev bound states appear as chiral Majorana edge modes. We calculate the energy spectrum of the edge modes and the resulting local density of states. It is found that the degenerate chiral Majorana edge modes for ${\cal N}=2$ are lifted off by applying Zeeman magnetic field along the parallel to the interface or the shift of the chemical potential by doping. The degeneracy of the chiral Majorana edge modes and its lifting are explained by two different winding numbers defined at the time-reversal invariant point of the edge momentum.
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