磁性斯格明子的研究现状和展望

磁性斯格明子是具有拓扑保护性质的纳米尺度涡旋磁结构.斯格明子主要存在于非中心对称的手性磁性材料以及界面镜面对称性破缺的磁性薄膜材料中.因具有实空间的非平庸拓扑性,磁性斯格明子展现出丰富新奇的物理学特性,例如拓扑霍尔效应,新兴电磁动力学等,为研究拓扑自旋电子学提供了新的平台.另一方面,由于其具有尺寸小,高稳定性和易操控的特性,磁性斯格明子在未来高密度,低能耗,非易失性计算和存储器件中也具有潜在应用.现阶段的研究已经初步发现一系列磁斯格明子材料,并证明能够通过电流操控室温下稳定的磁性斯格明子,但是室温下单个斯格明子的精确产生、湮灭以及探测在实验上仍具有挑战性.本文阐述了磁性斯格明子的基础理论以及动力学研究现状,并对现有的斯格明子材料和斯格明子的产生,湮灭以及探测方法进行了总结,最后还对未来磁性斯格明子的物理理论研究以及应用发展中的挑战和机遇进行了讨论.

Overview and outlook of magnetic skyrmions

Magnetic skyrmions are topologically protected nano-scale spin textures. They normally exist in chiral magnets and magnetic thin films with broken inversion symmetry. The size of skyrmion ranges from 1 nm to several hundred nanometers, depending on the material parameters. The spins of skyrmion wrap around the unit sphere exactly once, thus facilitating the unit topological charge of a skyrmion. Due to their non-trivial topology, skyrmions exhibit exotic physics such as the topological Hall effect (THE) and the emergent electrodynamics. Skyrmions show particle-like dynamics and can be driven with ultra-low current density. Furthermore, they can be created, annihilated, manipulated and detected by all-electric methods, making skyrmion a promising candidate for next-generation information storage and processing technologies. On the other hand, combining skyrmions with superconductors and topological insulators may also lead to intriguing physics and applications such as the topological quantum computing. Over the past few years, the creation, annihilation and detection of skyrmion at room temperature have already been demonstrated, but the precise control of single skyrmion with size below 10 nm is still a challenge. In this paper, we first review the fundamental physics of skyrmion, from its topology to its emergent dynamics. Physical mechanisms of the Dzyaloshinskii-Moriya interaction, the emergent electrodynamics and the THE are discussed. Then the skyrmion material systems, including chiral magnets, magnetic thin films, artificial skyrmion systems, frustrated magnets, bi-skyrmion materials and antiskyrmion materials, are comprehensively summarized. The optimizations of materials and potential new skyrmion materials are also proposed for different material systems. Methods of creating, annihilating and detecting skyrmions, which also cover potential application methods other than electrical methods, are discussed from both theoretical and experimental point of view. The energy efficiencies and reliabilities of different creation and annihilation methods and the sensitivities of different detection methods are still unclear, these current bottlenecks and possible avenues towards skyrmion-based spintronics are described. Finally, we address some possible future directions of skyrmion research, such as the antiferromagnetic skyrmion and skyrmions in topological insulators, which may lead to the discovery of peculiar topological quantum physics and materials.