Hui Hoi-Yin, Brydon P M R, Sau Jay D, Tewari S, Das Sarma S
Department of Physics, Condensed Matter Theory Center and Joint Quantum Institute, University of Maryland, College Park, Maryland 20742, USA.
Sci Rep. 2015 Mar 6;5:8880. doi: 10.1038/srep08880.
Majorana fermion (MF) excitations in solid state system have non-Abelian statistics which is essential for topological quantum computation. Previous proposals to realize MF, however, generally requires fine-tuning of parameters. Here we explore a platform which avoids the fine-tuning problem, namely a ferromagnetic chain deposited on the surface of a spin-orbit coupled s-wave superconductor. We show that it generically supports zero-energy topological MF excitations near the two ends of the chain with minimal fine-tuning. Depending on the strength of the ferromagnetic moment in the chain, the number of MFs at each end, n, can be either one or two, and should be revealed by a robust zero-bias peak (ZBP) of height 2 ne(2)/h in scanning tunneling microscopy (STM) measurements which would show strong (weak) signals at the ends (middle) of the chain. The role of an approximate chiral symmetry which gives an integer topological invariant to the system is discussed.
固态系统中的马约拉纳费米子（MF）激发具有非阿贝尔统计特性，这对于拓扑量子计算至关重要。然而，先前实现MF的提议通常需要对参数进行精细调节。在此，我们探索一个避免精细调节问题的平台，即沉积在自旋轨道耦合s波超导体表面的铁磁链。我们表明，它通常在链的两端附近支持零能拓扑MF激发，且只需进行最小程度的精细调节。根据链中铁磁矩的强度，每端的MF数量n可以是一个或两个，并且应该通过扫描隧道显微镜（STM）测量中高度为2ne(2)/h的稳健零偏压峰（ZBP）来揭示，该峰在链的两端（中间）会显示出强（弱）信号。我们还讨论了赋予系统整数拓扑不变量的近似手征对称性的作用。
