Lesser Omri, Saydjari Andrew, Wesson Marie, Yacoby Amir, Oreg Yuval
Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot 7610001, Israel.
Department of Physics, Harvard University, Cambridge, MA 02138.
Proc Natl Acad Sci U S A. 2021 Jul 6;118(27). doi: 10.1073/pnas.2107377118.
Topological superconductivity in quasi-one-dimensional systems is a novel phase of matter with possible implications for quantum computation. Despite years of effort, a definitive signature of this phase in experiments is still debated. A major cause of this ambiguity is the side effects of applying a magnetic field: induced in-gap states, vortices, and alignment issues. Here we propose a planar semiconductor-superconductor heterostructure as a platform for realizing topological superconductivity without applying a magnetic field to the two-dimensional electron gas hosting the topological state. Time-reversal symmetry is broken only by phase biasing the proximitizing superconductors, which can be achieved using extremely small fluxes or bias currents far from the quasi-one-dimensional channel. Our platform is based on interference between this phase biasing and the phase arising from strong spin-orbit coupling in closed electron trajectories. The principle is demonstrated analytically using a simple model, and then shown numerically for realistic devices. We show a robust topological phase diagram, as well as explicit wavefunctions of Majorana zero modes. We discuss experimental issues regarding the practical implementation of our proposal, establishing it as an accessible scheme with contemporary experimental techniques.
准一维系统中的拓扑超导是一种新型物质相，可能对量子计算产生影响。尽管经过多年努力，但该相在实验中的明确特征仍存在争议。这种模糊性的一个主要原因是施加磁场的副作用：诱导能隙态、涡旋和对准问题。在此，我们提出一种平面半导体 - 超导异质结构，作为在不向承载拓扑态的二维电子气施加磁场的情况下实现拓扑超导的平台。时间反演对称性仅通过对近邻超导体进行相位偏置来打破，这可以使用极小的通量或远离准一维通道的偏置电流来实现。我们的平台基于这种相位偏置与封闭电子轨迹中强自旋 - 轨道耦合产生的相位之间的干涉。使用一个简单模型对该原理进行了分析论证，然后针对实际器件进行了数值展示。我们展示了一个稳健的拓扑相图以及马约拉纳零模的显式波函数。我们讨论了关于我们提议的实际实施的实验问题，将其确立为一种可通过当代实验技术实现的方案。
