| Project/Area Number |
14540300
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
固体物性Ⅰ(光物性・半導体・誘電体)
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| Research Institution | Kyoto Institute of Technology |
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Principal Investigator |
TAKAGAHARA Toshihide Kyoto Institute of Technology, Electronics and Information Science, Professor, 工芸学部・電子情報工学科, 教授 (00111469)
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| Co-Investigator(Kenkyū-buntansha) |
KAMADA Hidehiko NTT Basic Research Laboratories, Senior Research Scientist, 主任研究員
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| Project Period (FY) |
2002 – 2004
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| Project Status |
Completed (Fiscal Year 2004)
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| Budget Amount *help |
¥3,300,000 (Direct Cost: ¥3,300,000)
Fiscal Year 2004: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 2003: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 2002: ¥1,700,000 (Direct Cost: ¥1,700,000)
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| Keywords | semiconductor quantum dot / coherent optical phenomena / Rabi oscillation / quantum state control / quantum coherence / multi-exciton states / spin relaxation |
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| Research Abstract |
Near-field scanning optical microscopy revealed many important features of semiconductor nanostructures. The unprecedented high spatial resolution of NSOM was achieved recently and a strikingly new feature in the single-dot spectroscopy was reported. Namely, the spatial extent of the luminescence corresponding to the transition from the biexciton state to the exciton state is remarkably narrower than that of the exciton to the ground state transition. This observation was interpreted in terms of the center-of-mass confinement of the biexciton state, namely a kind of the dead-layer model Although this model gives a qualitative interpretation, a more quantitative theory is necessary to estimate the ratio of the FWHM of the spatial extent of both luminescence patterns and to understand the quantum-dot-size dependence of that ratio. We developed such a theory and obtained a good agreement with experiments.
In recent years, a single electron in a single quantum dot or a single donor electron is extensively studied from the interest in the application to the quantum information processing. Especially, the electron spin decoherence time is one of the most important parameters which determine the performance figure of merit of the quantum information processing. We developed a theory to predict quantitatively the electron spin decoherence time and its temperature dependence and to clarify the temperature range in which the cross-over occurs between the regime dominated by the electron-phonon interaction and the regime governed by the hyperfine interaction with nuclear spins
Photon correlation measurements were done on two photons emitted in the cascade process from a biexciton state to the ground state through an exciton state and the two photons were found not to be entangled. The origin of the absence of entanglement was pointed out to be the exciton state splitting due to the anisotropic exchange interaction in a quantum dot with anisotropic shape.
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