Zhang Yuanyuan, Jiang Meizhen, Wu Zhen, Yang Qing, Men Yumeng, Cheng Lin, Liang Pan, Hu Rongrong, Jia Tianqing, Sun Zhenrong, Feng Donghai
State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200241, China.
College of Arts and Sciences, Shanghai Dianji University, Shanghai 201306, China.
J Phys Chem Lett. 2021 Oct 7;12(39):9481-9487. doi: 10.1021/acs.jpclett.1c02754. Epub 2021 Sep 24.
The electron spin relaxation processes are complicated in semiconductor quantum dots. Different spin relaxation mechanisms may result in an increased or decreased spin relaxation rate with the size. The information on size-dependent spin dynamics helps to clarify and better understand the underlying spin relaxation processes. We investigate the size dependence of the electron spin dynamics in negatively photocharged CdSe and CdS colloidal quantum dots by time-resolved ellipticity spectroscopy. It is revealed that the electron spin dephasings of photodoped electron in zero or weak magnetic fields are dominated by the electron-nuclear hyperfine interaction for all measured samples. The hyperfine-induced electron spin dephasing time is ∼1-2 ns at room temperature and decreases with decreasing the size . In addition to a size-dependent dephasing time that is directly proportional to , our measurements also show a size-independent time component, likely due to the laser-induced nuclear spin ordering.
在半导体量子点中，电子自旋弛豫过程较为复杂。不同的自旋弛豫机制可能导致自旋弛豫速率随尺寸增加或减小。尺寸依赖的自旋动力学信息有助于阐明并更好地理解潜在的自旋弛豫过程。我们通过时间分辨椭圆率光谱研究了负光充电的CdSe和CdS胶体量子点中电子自旋动力学的尺寸依赖性。结果表明，对于所有测量的样品，在零磁场或弱磁场中光掺杂电子的电子自旋去相位主要由电子-核超精细相互作用主导。在室温下，超精细诱导的电子自旋去相位时间约为1-2纳秒，且随尺寸减小而减小。除了与尺寸直接相关的去相位时间外（该时间与 成正比），我们的测量还显示出一个与尺寸无关的时间分量，这可能是由于激光诱导的核自旋有序化所致。
