铁基超导涡旋马约拉纳零能模探微 (The Emergent Vortex Majorana Zero Modes in an Iron-Based Superconductor)

作为马约拉纳零能模 (MZM) 的一种全新载体,具有拓扑能带结构的铁基超 导块材——拓扑铁基超导体——近年来引起了学术界的广泛关注。由于同时具 备单一材料、高温超导、强电子关联、拓扑能带等特质,拓扑铁基超导体成功规 避了本征拓扑超导体和近邻异质结体系在实现 MZM 上的困难,为马约拉纳物 理开辟了自赋性拓扑超导的新方向。时至今日,人们已经在多种拓扑铁基超导 体的磁通涡旋中测量到了纯净的 MZM。实验发现,铁基超导体系中演生的涡旋 MZM 信号明确、物理清晰,具有很好的应用前景。拓扑铁基超导体有望成长为研 究马约拉纳物理和制备拓扑量子比特最重要的材料体系之一。本文以 Fe(Te,Se) 为主要对象详细介绍了铁基超导马约拉纳载体的思想起源和研究进展。在阐明 Fe(Te,Se) 拓扑能带结构和零能涡旋束缚态基本实验事实的基础上,本文将逻辑 清晰地系统总结铁基超导涡旋演生MZM的主要实验观测和基本物理行为;借助 波函数、准粒子中毒等实验,解析 Fe(Te,Se) 单晶中的涡旋 MZM 演生机制;结 合现有马约拉纳理论,深入探讨铁基超导体中的马约拉纳对称性和准粒子拓扑 本质的实验测量。最后,本文采用“从量子物理到量子工程”的视角,综合分析 涡旋 MZM 在真实材料和实际实验中的鲁棒性,为未来潜在的工程应用提供有 益指导。本文以物理原理为线,注重理论与实验结合,旨在搭建经典马约拉纳理 论与新兴拓扑铁基超导体系之间的桥梁,帮助读者理解铁基超导涡旋中演生的 MZM。

The vortex of iron-based superconductors is emerging as a promising platform for Majorana zero mode, owing to a magic integration among intrinsic vortex winding, non-trivial band topology, strong electron-electron correlations, high-Tc superconductivity and the simplification of single material. It overcomes many difficulties suffered in heterostructure-based Majorana platforms, including small topological gap, interfacial contamination, lattice imperfections, and etc. Isolated zero-bias peaks have been found in vortex of several iron-based superconductors. So far, studies from both experimental and theoretical aspects strongly indicate the realization of vortex Majorana zero mode, with a potential to be applied to topological quantum computation. By taking Fe(Te,Se) superconductor as an example, here we review original idea and research progress of Majorana zero modes in this new platform. After introducing the identifications of topological band structure and real zero modes in vortex, we summarize the physics behaviors of vortex Majorana zero modes systematically. Firstly, relying on the behavior of the zero mode wave function and evidence of quasiparticle poisoning, we analyze the mechanism of emergence of vortex Majorana zero modes. Secondly, assisted with some well-established theories, we elaborate the measurements on Majorana symmetry and topological nature of vortex Majorana zero modes. After that, we switch from quantum physics to quantum engineering, and analyze the performance of vortex Majorana zero mode under real circumstances, which may potentially benefit the exploration of practical applications in the future. This review follows the physics properties of vortex Majorana zero modes, especially emphasizes the link between phenomena and mechanisms. It provides a chance to bridge the gap between the well-established theories and the newly discovered iron home of Majoranas.