Gül Önder, Zhang Hao, Bommer Jouri D S, de Moor Michiel W A, Car Diana, Plissard Sébastien R, Bakkers Erik P A M, Geresdi Attila, Watanabe Kenji, Taniguchi Takashi, Kouwenhoven Leo P
QuTech and Kavli Institute of Nanoscience, Delft University of Technology, Delft, The Netherlands.
Department of Physics, Harvard University, Cambridge, MA, USA.
Nat Nanotechnol. 2018 Mar;13(3):192-197. doi: 10.1038/s41565-017-0032-8. Epub 2018 Jan 15.
Majorana modes are zero-energy excitations of a topological superconductor that exhibit non-Abelian statistics. Following proposals for their detection in a semiconductor nanowire coupled to an s-wave superconductor, several tunnelling experiments reported characteristic Majorana signatures. Reducing disorder has been a prime challenge for these experiments because disorder can mimic the zero-energy signatures of Majoranas, and renders the topological properties inaccessible. Here, we show characteristic Majorana signatures in InSb nanowire devices exhibiting clear ballistic transport properties. Application of a magnetic field and spatial control of carrier density using local gates generates a zero bias peak that is rigid over a large region in the parameter space of chemical potential, Zeeman energy and tunnel barrier potential. The reduction of disorder allows us to resolve separate regions in the parameter space with and without a zero bias peak, indicating topologically distinct phases. These observations are consistent with the Majorana theory in a ballistic system , and exclude the known alternative explanations that invoke disorder or a nonuniform chemical potential.
马约拉纳费米子态是拓扑超导体的零能激发态，具有非阿贝尔统计特性。继有人提出在与s波超导体耦合的半导体纳米线中探测到马约拉纳费米子态之后，几项隧穿实验报告了具有特征性的马约拉纳费米子态信号。减少无序性一直是这些实验面临的主要挑战，因为无序性会模拟出马约拉纳费米子态的零能信号，使拓扑特性难以获得。在此，我们在表现出明显弹道输运特性的锑化铟纳米线器件中展示了特征性的马约拉纳费米子态信号。施加磁场并利用局部栅极对载流子密度进行空间控制，会产生一个零偏压峰，该峰在化学势、塞曼能和隧道势垒势的参数空间中的很大区域内都是稳定的。无序性的降低使我们能够分辨出参数空间中存在和不存在零偏压峰的不同区域，这表明存在拓扑性质不同的相。这些观测结果与弹道系统中的马约拉纳费米子态理论一致，并排除了那些援引无序性或非均匀化学势的已知替代解释。
