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Relaxation and Coherent Control of Quantum Dots

量子点的弛豫和相干控制

基本信息

批准号：
13852003
负责人：
MASUMOTO Yasuaki
金额：
$ 76.71万
依托单位：
University of Tsukuba
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (S)
财政年份：
2001
资助国家：
日本
起止时间：
2001 至 2005
项目状态：
已结题

项目摘要

(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.

(1)利用干涉双脉冲激发和时间积分检测InGaAs量子点共振光致发光光谱中的光学声子边带，测量了应力诱导InGaAs量子点最低能量电子跃迁的退相。利用累积光子回波技术研究了低温下CdSe和CuBr量子点中受限激子的均匀线宽。均匀宽度一般由“温度无关”项、“激子-二能级系统相互作用”项和“激子-限制声学声子相互作用”项之和给出。(2)外电场中InP和InGaAs量子点的光谱和时间特性表明，声子介导的弛豫过程比理论预测的要快得多。这一观测结果证明了预测的声子瓶颈效应的崩溃。(3)高灵敏度的外差探测光子回波使我们能够观察到来自一层应变诱导GaAs量子点和InP量子点的信号。在量子阱中形成的GaAs量子点中观察到的双激子拍频表明，与量子阱相比，双激子结合能额外增加。InP量子点中的光子回波在电场作用下表现出隧穿引起的退相和非指数衰减，反映了其非马尔可夫性质。(4)在掺电子的InP量子点中发现了三能级量子拍，在量子点中观察到了4种量子拍。这项研究创造了改变可调量子点的概念。(5)研究了电子掺杂InP量子点中的电子自旋弛豫，发现其弛豫时间可以达到亚毫秒级。(6)结果表明，在0.1T磁场下，p-InAs量子点中电子自旋弛豫时间由500 ps延长到4 ns。这表明了由随机取向的核自旋引起的电子自旋弛豫的有效抑制。