Displaceable magnetic skyrmions in ultrathin films on superconductors for configurable Majorana state

超导体超薄膜中的可位移磁性斯格明子，用于可配置的马约拉纳态

• 批准号: 403503586
• 负责人: Professor Dr. Yuriy Mokrousov, since 10/2019
• 金额: --
• 依托单位: Physikalisches Institut (PHI)
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 财政年份: 2018
• 资助国家: 德国
• 起止时间: 2017-12-31 至 2022-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/403503586?language=en
• 关键词: Displaceable; magnetic; skyrmions; ultrathin; films

Isolated skyrmions are of particular interest for magnetic memories since they can be moved by low current densities and their topologically enhanced stability. They have been observed in a wide range of polycrystalline metallic multilayers. However, in these polycrystalline metallic films, skyrmion mobility is often limited by pinning to structural defects. For epitaxial films, only few systems are known to stabilize magnetic skyrmions. Among them are the structures where the spatial inversion symmetry is broken in the bulk by the crystal structure itself, as in MnSi, or by interfaces such as Fe/Ir(111). In these systems, isolated skyrmions were reported under large magnetic fields (1 to 3 T). We recently discovered that magnetic skyrmions in Co/Ru(0001) are meta stable down to vanishing magnetic fields and can be moved when observed with magnetic STM tip. Ru is, however, superconducting below 500 mK and at magnetic fields below 7 mT, and it has been suggested that at the interface between a conventional superconductor and magnetic films displaying Skyrmions, Majorana fermions are formed. The main objectives of this project is to realize and theoretically describe Majorana states in the hybrid non-collinear magnetic-superconducting system Co/Ru(0001) or related systems, to laterally displace the observed skyrmions and associated Majorana states with help of STM, to understand the mechanism of the lateral displacement, to investigate the proximity effect in the magnetic layer and the evolution of the Majorana states. Ultimately, the entanglement of Majorana states and the braiding of the Majorana zero modes will be studied in order to investigate the potential to use skyrmions in Co/Ru as for topological quantum computing. The project relies on a close collaboration between experiment and theory. The partners have collaborated on the purely magnetic aspects of the materials system, before.

孤立的Skyrmions对磁记忆特别感兴趣，因为它们可以通过低电流密度移动，并且它们的拓扑结构增强了稳定性。它们已经在广泛的多晶金属多层膜中被观察到。然而，在这些多晶金属薄膜中，Skyrmion迁移率往往受到结构缺陷钉扎的限制。对于外延薄膜，只有几个已知的系统可以稳定磁天子。在这些结构中，空间反转对称性被晶体结构本身(如MnSi)或界面(如Fe/Ir(111))破坏。在这些系统中，孤立的Skyrmions在强磁场(1~3T)下被报道。我们最近发现，Co/Ru(0001)中的磁天子是亚稳定的，直到消失的磁场，并且可以用磁性STM针尖观察到移动。然而，在低于500mK和低于7mT的磁场下，Ru是超导的，并且有人认为在传统超导体和显示Skyrmions的磁性薄膜之间的界面上形成了Majorana费米子。本项目的主要目标是实现并从理论上描述非共线混合磁超导系统Co/Ru(0001)或相关系统中的Majorana态，利用扫描隧道显微镜对观测到的Skyrmions和伴随的Majorana态进行横向位移，了解横向位移的机制，研究磁层中的邻近效应和Majorana态的演化。最后，我们将研究Majorana态的纠缠和Majorana零模的编织，以探索利用Co/Ru中的Skyrmions进行量子拓扑计算的可能性。该项目依赖于实验和理论之间的密切合作。合作伙伴以前曾在材料系统的纯磁性方面进行过合作。