报告题目： Probing Impurity Spin Dynamics in CD1-xMnxSe Quantum Dots

报告人： John McGuire 教授（上海科技大学）

报告时间： 2023年6月1日（星期四）, 下午4：00

地点：致知楼3623

报告摘要：

As an electron and proton in vacuum can bind to form a hydrogen atom, so an electron-hole (e-h) pair in a dielectric environment can bind to form an exciton. Unlike the electron and proton of the hydrogen atom, though, the e-h pair of an exciton does not bind in vacuum but in a crystalline environment characterized by material-dependent lattice symmetries and degrees of freedom beyond those of the e-h pair, such as phonons and spins. The exciton wave function can be further modified by quantum confinement. I will discuss the interactions of excitons with the S=5/2 spin of Mn2+ ions in Cd1-xMnxSe colloidal quantum dots. Hopping of the hole and the electron in and out of the Mn2+ orbitals leads to an effective magnetic interaction between e-h pair and the Mn2+ spin. At low temperatures, these interactions can result in an excitonic polaron (bound state of an exciton and the locally polarized spin system) and enhanced exciton binding. The temperature at which polaron formation occurs depends on the dynamics of the Mn2+ spin-flip process and is not well characterized. I will describe how we use two-dimensional spectroscopy to probe the quantum mechanical dephasing of the exciton and through that probe the Mn2+ spin dynamics.

报告人简介：

John McGuire，上海科技大学研究员、副教授，跟加州大学伯克利分校的沈元壤教授读了博士而用了超快与非线性光学研究硅、水等表面的动力学。在美国洛斯阿拉莫斯国家实验室做了博士后探讨胶体量子点的多激子态。去上科大之前McGuire教授在美国密歇根州立大学任教，研究了石墨烯量子点、几层GaSe等低维材料。 从2018年他在上科大用二维光谱、二次谐波、时间分辨太赫兹光谱研究量子材料（低维、相关材料）的动力学与对称。他课题组目前在研究Cd1-xMnxSe里面的激子与Mn2+自旋的互相作用与自旋动力学，Hubbard激子，氧化材料薄膜的铁电与磁性的性质。