Total angular momentum conservation in laser-induced femtosecond magnetism
Total angular momentum conservation in laser-induced femtosecond magnetism
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DOI：
10.1103/physrevb.78.052407
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发表时间：
2008-08
影响因子：
3.7
通讯作者：
Guoping Zhang;T. George
中科院分区：
文献类型：
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作者：
Guoping Zhang;T. George
总角动量守恒是经典力学和量子力学的基本定律，但由于自旋动量不是经典量，因此总角动量守恒定律对飞秒激光诱导磁化过程中自旋动量变化的影响还远不明显。在这里，它表明，如果一个系统具有完整的旋转对称性，法律要求的自旋和轨道动量耦合，但没有真正的磁化线偏振光的变化。为了引起这种变化，这种对称性必须被打破。在固体中，转动对称性被平移对称性所提升，不同总角动量的自旋和轨道动量分量在某种程度上混合。这种混合是Bartelt [Appl. Phys. Lett. 90，162503（2007）]。其余未混合的部分占额外的自旋变化在三个独立的圆偏振激光实验。
Total angular momentum conservation is a fundamental law in classical and quantum mechanics, but since spin momentum is not a classical quantity, it is far from obvious how the law affects spin momentum change in laser-induced femtosecond magnetization. Here it is shown that if a system has full rotational symmetry, the law requires that the spin and orbital momenta are coupled, but there is no genuine magnetization change for linearly polarized light. To induce such a change, this very symmetry has to be broken. In solids, the rotational symmetry is lifted by the translational symmetry, and the spin and orbital momenta components of different total angular momenta mix to some extent. This mixing is the origin of the time-dependent total angular momentum as observed by Bartelt [Appl. Phys. Lett. 90, 162503 (2007)]. The remaining unmixed portion accounts for an extra spin change in three independent circularly polarized laser experiments.