Spin-current instability at a magnetic domain wall in a ferromagnetic superfluid: A generation mechanism of eccentric fractional skyrmions
Spin-current instability at a magnetic domain wall in a ferromagnetic superfluid: A generation mechanism of eccentric fractional skyrmions
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DOI：
10.1103/physreva.105.013328
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发表时间：
2021-09
影响因子：
2.9
通讯作者：
H. Takeuchi
中科院分区：
文献类型：
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作者：
H. Takeuchi
超冷原子的自旋超流体是研究自旋电流和织构的内在性质的理想材料，因为它们是在一个孤立的、无耗散的系统中实现的，没有杂质、位错和热涨落。这项研究从理论上揭示了自旋电流对自旋超流体中磁畴壁的影响。本文给出了零温下具有易轴各向异性的自旋为1的玻色-爱因斯坦凝聚体铁磁相的精确壁面解。玻色准粒子力学分析表明，当速度超过临界自旋流速度时，沿壁面的自旋流沿着变得不稳定，由于横向磁振子和波纹子之间的竞争而导致复杂的情况。我们的直接数值模拟表明，该系统有一个机制，以产生一个偏心的分数skyrmion，它具有分数拓扑电荷，但它的纹理是不类似的一个重子。这种机制与易轴磁体中传统skyrmions的产生相反。这些理论发现可以在与最近的超冷原子实验相同的情况下进行检验。从对称性自发破缺的普遍性来看，在具有相同对称性破缺的不同物理系统中，可能存在着类似的现象。
Spinful superfluids of ultracold atoms are ideal for investigating the intrinsic properties of spin current and texture because they are realized in an isolated, nondissipative system free from impurities, dislocations, and thermal fluctuations. This study theoretically reveals the impact of spin current on a magnetic domain wall in spinful superfluids. An exact wall solution is obtained in the ferromagnetic phase of a spin-1 Bose–Einstein condensate with easy-axis anisotropy at zero temperature. The bosonic-quasiparticle mechanics analytically show that the spin current along the wall becomes unstable if the velocity exceeds the critical spin-current velocities, leading to complicated situations because of the competition between transverse magnons and ripplons. Our direct numerical simulation reveals that this system has a mechanism to generate an eccentric fractional skyrmion, which has a fractional topological charge, but its texture is not similar to that of a meron. This mechanism is in contrast to the generation of conventional skyrmions in easy-axis magnets. The theoretical findings can be examined in the same situation as in a recent experiment on ultracold atoms. In terms of the universality of spontaneous symmetry breaking, unexplored similar phenomena are expected in different physical systems with the same broken symmetry.