Microscopic origin of subthermal magnons and the spin Seebeck effect
Microscopic origin of subthermal magnons and the spin Seebeck effect
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DOI：
10.1088/1367-2630/18/5/052002
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发表时间：
2016-01
影响因子：
3.3
通讯作者：
I. Diniz;A. Costa
中科院分区：
文献类型：
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作者：
I. Diniz;A. Costa
最近的实验证据表明，低能磁子是自旋塞贝克效应的主要贡献者。这种光谱相关性令人费解，因为在同一材料中的其他热流上没有观察到这种相关性。在这里，我们认为这种行为的物理起源是由声子介导的磁振子-磁振子散射，在这个过程中守恒了磁振子的数量。为了评估这种散射的重要性和特点，我们从一个微观模型出发，推导了有效的磁振子-声子相互作用，包括能带、屏蔽的电子-电子相互作用和电子-声子相互作用。与高阶磁振子散射不同，我们发现与声子的耦合引起的散射对于低能(或亚热)磁子来说非常小，但在能量较低的自旋流传输子以上的某个能量提供磁子上方急剧增加。
Recent experimental evidence points to low-energy magnons as the primary contributors to the spin Seebeck effect. This spectral dependence is puzzling since it is not observed on other thermocurrents in the same material. Here, we argue that the physical origin of this behavior is the magnon–magnon scattering mediated by phonons, in a process which conserves the number of magnons. To assess the importance and features of this kind of scattering, we derive the effective magnon–phonon interaction from a microscopic model, including band energy, a screened electron–electron interaction and the electron–phonon interaction. Unlike higher order magnon-only scattering, we find that the coupling with phonons induce a scattering which is very small for low-energy (or subthermal) magnons but increases sharply above a certain energy—rendering magnons above this energy poor spin-current transporters.