超快透射电子显微镜原位触发技术的发展及应用

Ultrafast transmission electron microscope (UTEM) is a growing electron microscopy technique that enables the observation of various transient processes with nanometer (even angstrom) spatial resolution. Since its powerful functioning, numerous applications in different fields (e.g. physics, chemistry and biology) have been proposed based on the UTEM technique. Triggering nonequilibrium state is the basic premise for the investigation of ultrafast dynamic processes. For example, to activate the selected phonon branch, energy matching between the photons and the phonons is usually required, and the investigation of magnetic dynamics always needs the well defined laser polarization. However, the UTEM technology is still at the developing stage, and the community is making great effort to improve this technology. For instance, people are trying to make the photo-induced nonequilibrium state tunable. In this project, we propose to add two important tunable degree of freedoms to the pump beam of the UTEM, i.e. wavelength continous tunability and polarization tunability. Then, the tunable UTEM will be used to study the dynamics and formation mechanism of charge order in strongly correlated materials. In addition, the interaction among charge, orbit, spin, and lattice will be also investigated. This project is not only important for the development of modern electron microscopy, but also provides a powerful equipment to solve many significant scientific problems.

超快透射电子显微镜（UTEM）是一项正在极力发展的电子显微学技术。它能够直接观测纳米、甚至原子尺度的多种瞬态过程，在物理学、化学和生物学等多个领域具有广泛应用前景。合理有效的触发非平衡态是研究超快动态过程的基本前提，例如激发特定频率的声子需要选择与之匹配激光波长；磁动力学的研究需要控制激光的偏振态。然而，很多UTEM关联技术还在发展完善过程中，学界正在积极的对其进行改进，如光诱导非平衡态触发条件的可控可操纵就是一个备受关注的问题。针对这一基本现状，本项目拟为UTEM的泵浦激光添加波长连续可调和偏振态可控两个重要功能，以适应UTEM在不同研究领域的应用。本项目还将使用触发条件可调控UTEM观测强关联体系中电荷序的动力学特性和形成机制，探讨电荷、轨道、自旋和晶格自由度之间互作用机制。本项目的顺利实施不仅对现代电子显微学技术的发展有重要促进意义，还能够为解决很多重大科学问题提供有力的设支撑。

超快透射电子显微镜（UTEM）具有纳米-亚皮秒量级的高时空分辨率，是一项国际上正在大力发展的高端实验技术。丰富的非平衡态触发手段能够为研究 量子材料的超快动力学过程提供重要技术支撑。在项目支持下，申请人为UTEM泵浦激光添加了波长可调谐，偏振态控制、脉宽展宽/压缩等功能，丰富了触发手段，并在量子材料的电子、自旋、晶格动力学研究中取得了一定进展。例如，通过研究硼氮纳米管和单壁碳纳米管的超快电子和结构动力学，发现瞬态电子结构变化可诱发晶格绝热动力学过程，同时晶格瞬态行为也可驱动材料电子结构变化，电子和晶格两自由度的动力学行为密切相关；在高时空分辨率下研究(Mn0.5Ni0.5)65Ga35合金的超快动力学，揭示了自旋、电子和晶格在时域空间的耦合规律；表征了1T-TaS2−xSex、YBa2Cu3O7-等强关联材料的微观结构，并在时域空间解析强关联材料中不同自由度的演化规律，进一步理解了电荷序及其它有序态的竞争与共存规律。