Ultrafast electron microscopy in material science*

Project supported by the National Basic Research Program of China (Grant No. 2015CB921300), the National Key Research and Development Program of China (Grant Nos. 2016YFA0300300, 2017YFA0504703, and 2017YFA0302900), the National Natural Science Foundation of China (Grant Nos. 11604372, 11474323, and 11774391), the “Strategic Priority Research Program (B)” of the Chinese Academy of Sciences (Grant No. XDB07020000), and the Scientific Instrument Developing Project of the Chinese Academy of Sciences (Grant No. ZDKYYQ20170002). Z. A. L acknowledges the financial support of the Hundred Talent Program B from CAS.
Yang Huaixin1, 2, Sun Shuaishuai1, Zhang Ming1, 2, Li Zhongwen1, 2, Li Zian1, Xu Peng1, Tian Huanfang1, Li Jianqi1, 2, 3, †
       

(color online) Direct observation of an optically induced CDW transition in 1T-TaSe2. (a) High-resolution STEM image and diffraction patterns of CDW modulation in 1T-TaSe2 obtained along the [001] zone-axis direction at room temperature. The inset at the top-right corner shows a schematic of the qC superstructure. (b) Diffraction patterns for time delays of −5, 2, and 5 ps after ultrafast laser excitation. The rotation of the satellite reflections is visible between −5 and 5 ps. (c) Intensity changes of satellite spots for qC and qIC as a function of the time delay. Reprinted from Ref. [48] with permission.