Spin Caloritronics in III-V-Semiconductors

我们建议探索电学和时间分辨光学方法研究III-V半导体异质结中热致自旋输运现象的可能性。在第一个焦点中，我们将通过光激光脉冲产生相干的自旋和电荷信息包。通过时间分辨的法拉第旋转(自旋敏感)和时间分辨的透射率(电荷敏感)的时空测量，在横向温度梯度中探测它们的热导率。通过产生与入射线偏振激光平行和垂直的初始自旋方向，我们期望能够探索自旋-轨道耦合对热致自旋输运的作用。在第二个焦点中，我们建议研究，类似于电压梯度，温度梯度本身是否会导致(I)自旋极化或(Ii)自旋电流。在(I)中，我们研究了内部磁场是否会产生自旋极化，而内部磁场是由热感应电场引起的。在(II)中，我们建议测量自旋-能斯特效应，对于自旋-能斯特效应，自旋电压与温度梯度的方向是横向的。自旋电压应通过磁光探头或使用铂电极作为探测器的光电电压或反向自旋霍尔效应的电测量来测量。

We propose to explore the potential of electrical and time-resolved optical methods for investigating heat-induced spin transport phenomena in III-V semiconductor heterostructures. In a first focus, we will generate coherent spin and charge packets by optical laser pulses. Their thermal conductivities shall be probed in a lateral temperature gradient by spatio-temporal measurements of time-resolved Faraday rotation (spin sensitive) and time-resolved transmission (charge sensitive). By generating initial spin directions parallel and perpendicular to the incident linearly polarized laser beam, we expect being able to explore the role of spin-orbit coupling for heat-induced spin transport. In a second focus, we propose to study whether, in analogy to a voltage gradient, a temperature gradient alone results in (I) a spin polarization or (II) a spin current. In (I), we study if a spin polarization will be created by internal magnetic fields, which are due to thermally-induced electric fields. In (II), we suggest to measure the spin- Nernst effect, for which a spin voltage is expected transverse to the direction of the thermal gradient. The spin voltage shall be measured either by magneto-optical probes or by electrical measurements of the photo-voltage or of the inverse spin Hall effect using platinum electrodes as detectors.