中文摘要：

利用时间分辨法拉第旋转光谱技术研究了室温下CdSe胶体量子点的自旋相干特性．获得了不同磁场下的自旋退相干时间，并分析了自旋退相干的物理机理．零磁场时量子点激子自旋退相干时问为102ps，主要受电子与核自旋之间的超精细相互作用所影响．当外加横向磁场强度为250mT时，激子自旋退相干时间为294ps；增大磁场强度，自旋退相干时间逐渐减小．在较强磁场环境中（≥250mT），量子点激子自旋动力学由非均匀退相干机制所主导．

英文摘要：

Time-resolved Faraday rotation spectroscopy is used to study the spin coherence in colloidal CdSe quantum dots at room tem- perature. Spin dephasing time and relevant dephasing mechanisms are analyzed in different transverse magnetic fields. The exciton spin-dephasing time is 102 ps in a zero magnetic field, which is affected by hyperfine interaction between electron and nuclear spins. In a transverse magnetic field of 250 mT, the exciton spin-dephasing time becomes 294 ps due to the fact that the presence of magnetic field makes the nuclear spin fluctuations unimportant. Further increasing the external magnetic field, the spin dephasing time becomes shorter. The magnetic field dependence of the exciton spin dynamics shows that the spin dynamics is dominated by the inhomogeneous dephasing in high magnetic fields （≥ 250 mT）.