Theory of spin magnetic quadrupole moment and temperature-gradient-induced magnetization
Theory of spin magnetic quadrupole moment and temperature-gradient-induced magnetization
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DOI：
10.1103/physrevb.99.024404
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发表时间：
2018-11
影响因子：
3.7
通讯作者：
A. Shitade;A. Daido;Y. Yanase
中科院分区：
文献类型：
--
作者：
A. Shitade;A. Daido;Y. Yanase
我们重新审视周期性晶体中自旋磁四极矩 (MQM) 的量子力学公式。之前的两次尝试彼此不一致；一种是规范相关的，另一种是规范不变的。在这里，我们通过计算非均匀系统中的自旋密度来定义自旋 MQM。我们的定义类似于电荷极化的定义，但结果是规范不变的并且与后一个一致。我们还提出了所谓的引力磁电（gravito-ME）效应，其中磁化强度是由温度梯度引起的。尽管引力-ME效应的Kubo公式在零温度下提供了非物理散度，但我们证明通过从Kubo公式中减去自旋MQM可以获得正确的磁化率。它在零温度下消失，并通过莫特关系与 ME 磁化率相关。我们明确计算了 Rashba 铁磁体中的 gravito-ME 磁化率并展示了其实验可行性。
We revisit a quantum-mechanical formula of the spin magnetic quadrupole moment (MQM) in periodic crystals. Two previous attempts were inconsistent with each other; one is gauge dependent and the other is gauge invariant. Here we define the spin MQM by calculating the spin density in a nonuniform system. Our definition is analogous to that of the charge polarization, but the result is gauge invariant and coincides with the latter previous one. We also formulate what we call gravitomagnetoelectric (gravito-ME) effect, in which the magnetization is induced by a temperature gradient. Although the Kubo formula for the gravito-ME effect provides an unphysical divergence at zero temperature, we prove that the correct susceptibility is obtained by subtracting the spin MQM from the Kubo formula. It vanishes at zero temperature and is related to the ME susceptibility by the Mott relation. We explicitly calculate the gravito-ME susceptibility in a Rashba ferromagnet and show its experimental feasibility.