| Project/Area Number |
15204028
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| Research Category |
Grant-in-Aid for Scientific Research (A)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Condensed matter physics I
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| Research Institution | The University of Tokyo |
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Principal Investigator |
TARUCHA Seigo THE UNIVERSITY OF TOKYO, GRADUATE SCHOOL OF ENGINEERING, PROFESSOR, 大学院工学系研究科, 教授 (40302799)
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| Co-Investigator(Kenkyū-buntansha) |
OIWA Akira THE UNIVERSITY OF TOKYO, GRADUATE SCHOOL OF ENGINEERING, LECTURER, 大学院工学系研究科, 講師 (10321902)
YAMAMOTO Michihisa THE UNIVERSITY OF TOKYO, GRADUATE SCHOOL OF ENGINEERING, ASSISTANT, 大学院工学系研究科, 助手 (00376493)
ONO Keiji THE UNIVERSITY OF TOKYO, GRADUATE SCHOOL OF ENGINEERING, RIKEN, RESEARCHER, 研究員 (00302802)
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| Project Period (FY) |
2003 – 2006
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| Project Status |
Completed (Fiscal Year 2006)
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| Budget Amount *help |
¥48,750,000 (Direct Cost: ¥37,500,000、Indirect Cost: ¥11,250,000)
Fiscal Year 2006: ¥4,420,000 (Direct Cost: ¥3,400,000、Indirect Cost: ¥1,020,000)
Fiscal Year 2005: ¥12,350,000 (Direct Cost: ¥9,500,000、Indirect Cost: ¥2,850,000)
Fiscal Year 2004: ¥6,370,000 (Direct Cost: ¥4,900,000、Indirect Cost: ¥1,470,000)
Fiscal Year 2003: ¥25,610,000 (Direct Cost: ¥19,700,000、Indirect Cost: ¥5,910,000)
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| Keywords | Semiconductor physics / Quantum dot / Spintronics / Mesoscopic system / 半導体 / スピン / 核スピン |
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| Research Abstract |
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.
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