Development of novel detection method of spin coherence and application to rapid control of electron spins

本研究旨在建立自旋相位光栅概念，以提取半导体纳米结构中电子（或空穴、原子核和激子）的最大自旋相干性。不同泵浦偏振组合下的三脉冲四波混频显示了自旋相位光栅的形成。为了抑制核自旋极化波动引起的自旋退相干，我们将CdTe作为纳米结构材料，成功地观察到核自旋小极化。此外，还发现了驻留电子极化的时间分辨Kerr旋转信号中负相移的产生机制是由于负离子中的快速空穴自旋弛豫。

This study aims at the establishment of spin phase grating concept to extract the maximum spin coherence of electron (or hole, nucleus, and exciton) in semiconductor nanostructures. 3-pulse four wave mixing with various pump polarization combinations revealed the formation of a spin phase grating. To suppress the spin decoherence due to the fluctuation of nuclear spin polarization, we used the CdTe for the nanostructure materials and succeeded to observe the small nuclear spin polarization. Moreover, generation mechanism of the negative phase shift in time-resolved Kerr rotation signals of the resident electron polarization was found to be due to the fast hole spin relaxation in negative trions.