Yan Tengfei, Ye Jialiang, Qiao Xiaofen, Tan Pingheng, Zhang Xinhui
State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, P.O. Box 912, Beijing 100083, P. R. China.
State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, P.O. Box 912, Beijing 100083, P. R. China and College of Materials Science and Opto-electronic Technology, University of Chinese Academy of Sciences, Beijing 100049, P. R. China.
Phys Chem Chem Phys. 2017 Jan 25;19(4):3176-3181. doi: 10.1039/c6cp07208a.
The newly developed two-dimensional layered materials provide a perfect platform for valley-spintronics exploration. To determine the prospect of utilizing the valley degree of freedom, it is of great importance to directly detect and understand the valley dynamics in these materials. Here, the exciton valley dynamics in monolayer WSe is investigated by the two-color pump-probe magneto-optical Kerr technique. By tuning the probe photon energy in resonance with the free excitons and trions, the valley relaxation time of different excitonic states in monolayer WSe is determined. Valley relaxation time of the free exciton in monolayer WSe is confirmed to be several picoseconds. A slow valley polarization relaxation process is observed to be associated with the trions, showing that the valley lifetime for trions is one order of magnitude longer than that of free excitons. This finding suggests that trion can be a good candidate for valleytronics applications.
新开发的二维层状材料为谷自旋电子学探索提供了一个完美的平台。为了确定利用谷自由度的前景，直接检测和理解这些材料中的谷动力学至关重要。在此，通过双色泵浦-探测磁光克尔技术研究了单层WSe中的激子谷动力学。通过将探测光子能量调谐到与自由激子和三重态共振，确定了单层WSe中不同激子态的谷弛豫时间。单层WSe中自由激子的谷弛豫时间被证实为几皮秒。观察到一个缓慢的谷极化弛豫过程与三重态有关，表明三重态的谷寿命比自由激子的谷寿命长一个数量级。这一发现表明，三重态可以成为谷电子学应用的良好候选者。
