Imaging Spectroscopy of Exciton Spin Diffusion and Relaxation in Quantum Structure Semiconductors

量子结构半导体中激子自旋扩散和弛豫的成像光谱

基本信息

批准号：
12640320
负责人：
ADACHI Satoru
金额：
$ 2.5万
依托单位：
Hokkaido University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2000
资助国家：
日本
起止时间：
2000 至 2001
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-12640320/
关键词：
imaging spin diffusion spin relaxation quantum structure semiconductors 量子構造

项目摘要

In recent years, people have much interest on "spin electronics" such as spin transistors, where electronic spin plays more important role than its charge in semiconductors. Then knowledge of the spin relaxation and spin diffusion is one of keys for success. Nevertheless those physical mechanisms in quantum structures are not well known. Under this background, We studied the diffusion and relaxation of exciton spin in quantum well structures. For this purpose, we utilized the four-wave-mixing spectroscopy with spin grating. Two pump pulses generated the exciton density grating near the sample surface in the co-linear polarizations. For the cross-linear polarizations, the pump pulses cannot interfere and therefore uniform exciton density is created. But the mixture of up-spin and down-spin of exciton changes according to the spatial position and thus the spin grating can be created. The pitch of both density and spin gratings can adjust by the crossing angle between the pump pulses. The time-delayed probe pulse diffracted from those gratings gives the decay rate of the gratings that includes the information about the relaxation and diffusion of the spin and density according to the character of the created grating. So, we could measure the spin relaxation ; spin diffusion constant, recombination and density diffusion constant in the same system. In the result, we obtained that spin diffusion rate is 3.5-times larger than density diffusion. This result is for the first time under my knowledge.

近年来，人们对“自旋电子”（例如自旋晶体管）非常感兴趣，在该旋转晶体管中，电子旋转在半导体中的电荷起着更重要的作用。然后，了解自旋松弛和自旋扩散是成功的关键之一。然而，量子结构中的这些物理机制尚不清楚。在这种背景下，我们研究了激子自旋在量子井结构中的扩散和松弛。为此，我们利用了带有自旋光栅的四波混合光谱。两种泵脉冲在共线性极化的样品表面附近产生激子密度光栅。对于跨线性极化，泵脉冲不能干扰，因此会产生均匀的激子密度。但是，激子的上旋和向下旋转的混合物根据空间位置而变化，从而可以创建自旋光栅。密度和自旋光栅的螺距可以通过泵脉冲之间的交叉角度调节。从这些光栅中衍射的时间延迟的探针脉冲给出了光栅的衰减速率，其中包括根据创建的光栅的特征，包括有关旋转和密度的松弛和扩散的信息。因此，我们可以测量自旋放松。同一系统中的自旋扩散常数，重组和密度扩散常数。结果，我们获得了自旋扩散速率比密度扩散大的3.5倍。这个结果是我所知的第一次。