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arXiv 2005.13238cond-mat.mes-hall
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超快退磁后瞬态畴壁Skyrmions的出现

Emergence of Transient Domain Wall Skyrmions after Ultrafast Demagnetisation

Serban Lepadatu

摘要:

众所周知,超快激光脉冲可以用来确定性地切换磁化强度并产生Skyrmion,但是在超快退磁后确定性地产生单个Néel Skyrmion仍然是一个悬而未决的问题。在这里,我们显示畴壁skyrmions也出现在系统中的破坏反转对称性暴露于超快激光脉冲后,携带一个整数拓扑电荷。虽然畴壁skyrmion不出现在松弛状态下,由于快速的热衰变遵循阿克里乌斯定律,他们发挥了关键作用,控制最终的skyrmion人口通过湮灭与skyrmion相反的拓扑电荷,与所得的skyrmion状态遵循泊松分布。使用单次线性偏振激光脉冲,以及圆偏振激光脉冲的训练,我们表明,当一个高度的无序被创建,成核一个单一的Néel skyrmion的可能性是伴随着成核的skyrmion与畴壁skyrmion对的可能性,这将导致自湮灭崩溃。

英文摘要:

It is known that ultrafast laser pulses can be used to deterministically switch magnetisation and create skyrmions, however the deterministic creation of a single Néel skyrmion after ultrafast demagnetisation remains an open question. Here we show domain wall skyrmions also emerge in systems with broken inversion symmetry after exposure to an ultrafast laser pulse, carrying an integer topological charge. Whilst domain wall skyrmions do not appear in the relaxed state due to quick thermal decay following an Arrhenius law, they play a key role in controlling the final skyrmion population through annihilations with skyrmions of opposite topological charge, with the resultant skyrmion states following a Poisson distribution. Using single-shot linearly polarised laser pulses, as well as a train of circularly polarised laser pulses, we show that when a high degree of disorder is created, the possibility of nucleating a single Néel skyrmion is accompanied by the possibility of nucleating a skyrmion with domain wall skyrmion pair, which results in a self-annihilation collapse.

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