laser诱导退磁中的自旋热点
Hot spin spots in the laser-induced demagnetization
摘要：
激光诱导的飞秒磁性同时依赖于两个独特的贡献：（a）激光场和磁性系统之间的光学偶极相互作用（ODI）和（b）两个过渡态之间的自旋期望值变化（SEC）。令人惊讶的是，到目前为止，还没有研究同时考虑到这两种贡献。在这里，我们通过引入光学自旋发生器的新概念来做到这一点，它是SEC和ODI在过渡态之间的产物。在铁磁镍中，我们的第一性原理计算表明，光学自旋产生子的值越大，动态自旋矩变化越大。这个简单的生成元直接将每个晶体动量k点处的随时间变化的自旋矩变化ΔMk z（t）与其固有的电子结构和磁性联系起来。这些自旋热点是光自旋发生器的直接表现，应该是未来研究的重点。
英文摘要：
Laser-induced femtosecond magnetism or femtomagnetism simultaneously relies on two distinctive contributions: (a) the optical dipole interaction (ODI) between a laser field and a magnetic system and (b) the spin expectation value change (SEC) between two transition states. Surprisingly, up to now, no study has taken both contributions into account simultaneously. Here we do so by introducing a new concept of the optical spin generator, a product of SEC and ODI between transition states. In ferromagnetic nickel, our first-principles calculation demonstrates that the larger the value of optical spin generator is, the larger the dynamic spin moment change is. This simple generator directly links the time-dependent spin moment change ΔMk z (t) at every crystal- momentum k point to its intrinsic electronic structure and magnetic properties. Those hot spin spots are a direct manifestation of the optical spin generator, and should be the focus of future research.
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