磁性霍普夫离子的可逆与不可逆动力学拓扑转变
Reversible and irreversible dynamical topological transitions of magnetic Hopfions
AI总结：
研究磁性霍普夫离子在交变磁场下动力学，通过三维微磁模拟等，发现弱场下有不可逆拓扑重构，强场下有可逆场锁定拓扑切换，场振幅和频率是控制旋钮，切换源于低频集体运动非线性延续或高频场锁定。
AI中文摘要：
磁性霍普夫离子是具有非零霍普夫不变量的三维拓扑孤子，为三维自旋电子学提供了一个有前景的平台。尽管其静态稳定化已被广泛研究，但在交变磁场下的非线性动力学仍很大程度未被探索。我们通过三维微磁模拟和解析模式分析表明，交变磁场驱动受限磁性霍普夫离子的两种定性不同的动力学状态。在弱场状态下，本征霍普夫离子模式的共振激发会引发非线性不稳定性以及从霍普夫离子到环面的不可逆拓扑重构。相反，在强场状态下，系统在吉赫兹频率下经历可逆的场锁定拓扑切换，磁化强度在拓扑平凡的铁磁构型和霍普夫离子状态之间周期性交替。切换路径由驱动频率选择：2吉赫兹的场驱动与低频集体响应相关的呼吸路径，而40吉赫兹的场产生由强塞曼扭矩驱动的进动和场锁定控制的非共振旋转路径。这些结果将场振幅和频率确定为独立的控制旋钮，并揭示可逆霍普夫离子切换可源于低频集体运动的非线性延续或非共振高频场锁定。
英文摘要：
Magnetic Hopfions are three-dimensional (3D) topological solitons characterized by a nonzero Hopf invariant and offer a promising platform for 3D spintronics. While their static stabilization has been widely studied, their nonlinear dynamics under alternating magnetic (AM) fields remain largely unexplored. We show, using 3D micromagnetic simulations and analytical mode analysis, that an AM field drives two qualitatively distinct dynamical regimes of a confined magnetic Hopfion. In the weak-field regime, resonant excitation of intrinsic Hopfion modes induces a nonlinear instability and an irreversible topological reconfiguration from a Hopfion to a toron. In contrast, in the strong-field regime, the system undergoes reversible field-locked topological switching at GHz frequencies, with the magnetization periodically alternating between a topologically trivial ferromagnetic configuration and a Hopfion state. The switching pathway is selected by the driving frequency: a 2 GHz field drives a breathing pathway associated with the low-frequency collective response, whereas a 40 GHz field produces a nonresonant rotational pathway governed by strong Zeeman-torque-driven precession and field locking. These results identify field amplitude and frequency as independent control knobs and reveal that reversible Hopfion switching can arise either from nonlinear continuation of low-frequency collective motion or from nonresonant high-frequency field locking.
