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Dynamics study of few-electron zero-dimensional spin system

少电子零维自旋系统动力学研究

基本信息

批准号：
15204028
负责人：
TARUCHA Seigo
金额：
$ 31.2万
依托单位：
The University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (A)
财政年份：
2003
资助国家：
日本
起止时间：
2003 至 2006
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-15204028/
关键词：
Semiconductor physics Quantum dot Spintronics Mesoscopic system 半導体スピン核スピン

项目摘要

In this project we have developed novel semiconductor nanostructures and explored dynamics of interacting zero-dimensional electrons confined to the nanostructures. The main topics study here are 1. Interaction of few-electrons in quantum dots and 2. Electron-nuclei spin coupling in quantum dots.1.We newly developed coupled quantum dot-quantum wire devices and demonstrated the spin-filtering effect for electrons tunneling through the dot in the regime of filling factor between 2 and 4, using the quantum wire as a spin-selective contact lead. To study the spin robustness in this tunneling we prepared a quantum dot with an electrostatically coupled quantum point and used the quantum point contact as a charge detector to directly measure the spin relaxation time, and assigned thus obtained relaxation time to the effect of spin-orbit interaction. We developed a new electrical pump-probe technique to measure spin relaxation time for vertically coupled double quantum dot and found that the measured relaxation time was significantly affected by hyperfine coupling to nuclear spin. We started a new topic about transport properties of an InAs self-assembled quantum dot with nano-gap electrodes, and found the Kondo effect for the first time in system of self-assembled quantum dots and discussed the effect of spin-orbit interaction, which is assumed to be strong in this InAs system.2.We first succeeded in both electrically and magnetically controlling the hyperfine coupling in a double quantum dot and achieved a high degree of nuclear polarization of ~50%. We also applied this technique to derive an exchange coupling energy with detuning between two quantum dot levels as a parameter, and demonstrated existence of stable region of exchange coupling with respect to the detuning. With the knowledge of electron spin-nuclear spin coupling obtained here and using an NMR technique, we first demonstrated coherent manipulation of nuclear spin in quantum dots.

在这个项目中，我们开发了新的半导体纳米结构，并探讨了相互作用的零维电子局限于纳米结构的动力学。本文研究的主要内容有：1.量子点中的少电子相互作用和2。量子点中的电子-原子核自旋耦合：1.利用量子线作为自旋选择性接触引线，在填充因子为2 ~ 4的情况下，我们研制了量子点-量子线耦合器件，并证明了电子隧穿量子点时的自旋过滤效应。为了研究这种隧穿中的自旋鲁棒性，我们制备了具有静电耦合量子点的量子点，并使用量子点接触作为电荷检测器来直接测量自旋弛豫时间，并将由此获得的弛豫时间分配给自旋轨道相互作用的影响。我们发展了一种新的电抽运-探测技术来测量垂直耦合双量子点的自旋弛豫时间，发现超精细耦合对自旋弛豫时间的影响很大。我们开创了InAs自组装量子点输运性质的新课题，首次发现了自组装量子点体系中的Kondo效应，并讨论了自旋轨道相互作用的影响，2.我们首次成功地在双量子点中实现了对超精细耦合的电磁控制，并获得了很高的量子效率。核极化度约为50%。我们还应用这种技术，以两个量子点能级之间的失谐量为参数，导出了交换耦合能，并证明了交换耦合稳定区的存在。利用我们得到的电子自旋-核自旋耦合的知识和核磁共振技术，我们首次证明了量子点中核自旋的相干操纵。