2005 Fiscal Year Final Research Report Summary
Relaxation and Coherent Control of Quantum Dots
| Project/Area Number |
13852003
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| Research Category |
Grant-in-Aid for Scientific Research (S)
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| Allocation Type | Single-year Grants |
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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 | University of Tsukuba |
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Principal Investigator |
MASUMOTO Yasuaki University of Tsukuba, Graduate School of Pure and Applied Sciences, Professor, 大学院・数理物質科学研究科, 教授 (60111580)
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| Co-Investigator(Kenkyū-buntansha) |
IKEZAWA Michio University of Tsukuba, Graduate School of Pure and Applied Sciences, Research Associate, 大学院・数理物質研究科, 助手 (30312797)
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| Project Period (FY) |
2001 – 2005
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| Keywords | quantum dot / phase relaxation / exciton / energy relaxation / photon echo / quantum beat / InP / spin |
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| Research Abstract |
(1) Dephasing of the lowest-energy electronic transition of stress-induced InGaAs quantum dots was measured by the interferometric double pulse excitation and time-integrated detection of optical-phonon sideband in their resonant-photoluminescence spectra. Homogeneous linewidth of confined excitons in CdSe and CuBr quantum dots was investigated at low temperatures by means of accumulated photon echo. Homogeneous width is universally given by the sum of "temperature-independent" term, "exciton-two level system interaction" term and "exciton-confined acoustic phonon interaction" term.
(2) Spectral and temporal behavior of photoluminescence of site-selectively excited InP and InGaAs quantum dots in external electric field showed fast phonon mediated relaxation processes is much faster than predicted theoretically. This observation demonstrates the breakdown of the predicted phonon bottleneck effect.
(3) Highly sensitive heterodyne-detected photon echo enabled us to observe the signal from one layer of strain-induced GaAs quantum dots and InP quantum dots. A biexcitonic beat observed in GaAs quantum dots formed in the quantum well shows the additional increase in the biexciton binding energy compared with that of the quantum well. The photon echo in InP quantum dots under the electric field showed tunneling-induced dephasing and decayed nonexponentially, reflecting its non-Markovian nature.
(4) Trionic quantum beat was discovered in eletron-doped InP quantum dots and 4 kinds of quantum beats were observed in quantum dots. The study created the concept of change tunable quantum dots.
(5) Electron spin relaxation in electron-doped InP quantum dots was investigated and found to reach the submillisecond range.
(6) It was shown that electron spin relaxation time of 500 ps observed in p-InAs quantum dots was elongated to 4 ns under the magnetic field of 0.1 T. This shows the efficient suppression of electron spin relaxation caused by randomly oriented nuclear spins.
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