报告人：Hui Zhao，堪萨斯大学

报告时间：6月14日下午3：00

报告地点：物理系三楼报告厅

报告题目：Nonlinear optics with ballistic charge and spin currents in semiconductors

报告摘要：Electronic transport on nanometer dimensions is of fundamental importance in semiconductor nano-electronics and spintronics. I will discuss our recent experimental studies of ballistic charge and spin transport on nanometer length scales by using ultrafast nonlinear optical techniques. I will discuss optical injection of ballistic charge and spin currents through a coherent control technique utilizing quantum interference between one-photon and two-photon absorption pathways. I will then describe how to study the dynamics of these ballistic currents by tracking the position of the electrons with 100 femtosecond temporal resolution and sub-nanometer spatial resolution. Using these techniques, we have observed intrinsic inverse spin Hall effect, and studied ballistic charge and spin transport in several semiconductors including GaAs, silicon and germanium. Following a theoretical prediction by Jing Wang, Bang-Fen Zhu (Tsinghua University) and Ren-Bao Liu (Chinese University of Hongkong), we have observed a nonlinear optical effect, second-harmonic generation, induced by a pure spin current. Finally, I will discuss our latest experiment on using the second-harmonic generation technique to study coherent plasma oscillation in semiconductors.