Zhang K L, Wang P, Song Z
School of Physics, Nankai University, Tianjin, 300071, China.
Sci Rep. 2019 Mar 21;9(1):4978. doi: 10.1038/s41598-019-41529-y.
We study a Kitaev model on a square lattice, which describes topologically trivial superconductor when gap opens, while supports topological gapless phase when gap closes. The degeneracy points are characterized by two vortices in momentum space, with opposite winding numbers. We show rigorously that the topological gapless phase always hosts a partial Majorana flat band edge modes in a ribbon geometry, although such a single band model has zero Chern number as a topologically trivial superconductor. The flat band disappears when the gapless phase becomes topologically trivial, associating with the mergence of two vortices. Numerical simulation indicates that the flat band is robust against the disorder.
我们研究了正方形晶格上的基泰耶夫模型，当能隙打开时，该模型描述拓扑平凡的超导体，而当能隙关闭时，支持拓扑无隙相。简并点由动量空间中的两个具有相反缠绕数的涡旋表征。我们严格证明，尽管作为拓扑平凡超导体的这种单带模型的陈数为零，但拓扑无隙相在带状几何结构中总是存在部分马约拉纳平带边缘模式。当无隙相变为拓扑平凡时，平带消失，这与两个涡旋的合并有关。数值模拟表明平带对无序具有鲁棒性。
