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中国物理学会期刊

Corbino圆盘中斯格明子的集体动力学研究

Collective dynamics of skyrmions in a Corbino disk

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  • 本文基于点粒子分子动力学模型,研究了Corbino圆盘中斯格明子的静态构型及其在径向电流驱动下的集体动力学行为。结果表明,在无外驱动时,体系在边界限域与粒子间排斥相互作用的共同作用下形成稳定的同心壳层结构,其静态排布与介观超导圆盘中的涡旋壳层构型相似。对于典型的多壳层结构,随着驱动电流增大,体系经历了由整体刚性转动向壳层解锁剪切转动的转变;在更强驱动下,内层斯格明子逐步向外层迁移,最终演化为单层环状结构。对于粒子数较多的体系,在完全单层化之前,由于外层局域密度升高和粒子间相互作用增强,体系还会出现再刚化现象,并伴随一定的结构重构。研究表明,强马格努斯力与非均匀驱动、边界限域及粒子间相互作用的共同作用,使Corbino几何中的斯格明子表现出不同于弱马格努斯力体系(如超导涡旋)的丰富非平衡动力学行为。本文结果可为理解受限几何中斯格明子的集体运动规律及其在自旋电子学器件中的潜在应用提供参考。

     

    Molecular dynamics simulations based on a particle model are performed to investigate the static configurations and driven collective dynamics of skyrmions confined in a Corbino disk. In this model, skyrmions are treated as interacting particles subject to the damping force, the Magnus force, the repulsive skyrmion-skyrmion interaction, the boundary confinement, and an external drive. The Corbino geometry produces a nonuniform driving force associated with a radial current, so that skyrmions at different radial positions experience different effective driving strengths. This provides a simple platform for studying shell locking, shear motion, and structural rearrangements in confined skyrmion assemblies. In the absence of an external drive, the competition between the boundary confinement and the repulsive skyrmionskyrmion interaction leads to stable concentric shell structures. These shell configurations are similar to the vortex shell structures in mesoscopic superconducting disks, because the Magnus force vanishes in the static state and the equilibrium arrangement is mainly determined by the confinement and interparticle repulsion. When a weak drive is applied, skyrmions in different shells rotate with nearly the same angular velocity, indicating that the whole assembly is locked into a rigidly rotating state. As the drive is increased beyond a small critical value, the shell locking is broken. Different shells then rotate with different angular velocities, and the system enters a shear-rotation state. Under stronger driving, the large Magnus force induces an outward radial drift in addition to the azimuthal motion. As a result, skyrmions initially located in the inner shells migrate outward one by one. This process changes the shell occupations discretely and eventually drives the system from a multi-shell configuration into a single-shell ring. For systems with larger particle numbers, the evolution is more complex. Before the final single-shell state is reached, the compression of skyrmions near the outer boundary increases the local density and enhances the effective elastic coupling between neighboring skyrmions. Consequently, the system can recover a nearly rigid rotation after entering the shear-rotation regime, giving rise to a re-entrant rigidly rotating state. This re-entrant rigid rotation is accompanied by discrete structural rearrangements, reflecting the strong coupling between shell reconstruction and collective motion. These results demonstrate that the interplay among the strong Magnus force, the nonuniform Corbino drive, the boundary confinement, and the interparticle interaction produces a sequence of nonequilibrium dynamical regimes, including rigid rotation, shear rotation, shell reconstruction, single-shell formation, and re-entrant rigid rotation. The dynamics are qualitatively different from those in weak-Magnus-force systems such as superconducting vortices. The present work provides a simple physical picture for understanding the collective motion of skyrmions in confined geometries and may be useful for the design of Corbino-based skyrmionic devices.

     

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