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arXiv 1505.00522cond-mat.mes-hallcond-mat.str-el
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高拓扑数磁skyrmions与拓扑保护耗散结构

High-topological-number magnetic skyrmions and topologically protected dissipative structure

Xichao Zhang, Yan Zhou, Motohiko Ezawa

摘要:

拓扑数为1的磁skyrmion($Q=1$)是具有Dzyaloshinskiiii-Moriya相互作用的非线性$σ$模型中一种著名的纳米涡旋自旋结构。在这里,我们表明,磁skyrmion与拓扑数为2($Q=2$)可以创建和稳定的垂直自旋极化电流,但它不能作为一个静态稳定的激发存在。含$Q=2$的磁Skyrmion是一种非平衡动力学物体,它依赖于电流注入的能量与Gilbert阻尼的能量耗散之间的平衡。一旦它被创建,它就成为一个拓扑保护对象,免受包括注入电流本身在内的各种变量的波动。因此,我们可以称之为拓扑保护耗散结构。通过研究磁化强度分布、拓扑电荷密度和能量密度的演化,阐明了含$Q=2$的磁skyrmion的成核和破坏机制.我们的结果对于研究具有更高拓扑数的磁skyrmions的非平凡拓扑是有用的。

英文摘要:

The magnetic skyrmion with the topological number of unity ($Q=1$) is a well-known nanometric swirling spin structure in the nonlinear $σ$ model with the Dzyaloshinskii-Moriya interaction. Here, we show that magnetic skyrmion with the topological number of two ($Q=2$) can be created and stabilized by applying vertical spin-polarized current though it cannot exist as a static stable excitation. Magnetic skyrmion with $Q=2$ is a nonequilibrium dynamic object, subsisting on a balance between the energy injection from the current and the energy dissipation by the Gilbert damping. Once it is created, it becomes a topologically protected object against fluctuations of various variables including the injected current itself. Hence, we may call it a topologically protected dissipative structure. We also elucidate the nucleation and destruction mechanisms of the magnetic skyrmion with $Q=2$ by studying the evolutions of the magnetization distribution, the topological charge density as well as the energy density. Our results will be useful for the study of the nontrivial topology of magnetic skyrmions with higher topological numbers.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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