Coherent Lattice Wobbling and Out-of-Phase Intensity Oscillations of Friedel Pairs Observed by Ultrafast Electron Diffraction
Coherent Lattice Wobbling and Out-of-Phase Intensity Oscillations of Friedel Pairs Observed by Ultrafast Electron Diffraction
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DOI：
10.1021/acsnano.0c02643
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发表时间：
2020-07-28
期刊：
影响因子：
17.1
通讯作者：
Huang, Shengxi
中科院分区：
文献类型：
--
作者：
Qian, Qingkai;Shen, Xiaozhe;Huang, Shengxi
在超快电子衍射（UED）中检验弗里德尔定律对于全面了解材料的原子结构及其动态响应具有重要意义。在这里，单斜碲化镓（GaTe），作为一个低对称性，层状晶体相比，许多其他的二维材料，兆电子伏UED研究。观察到Friedel对布拉格峰强度的强异相振荡，这不遵守Friedel定律。所证明的保存镜像对称性和支持的运动学和动力学散射模拟，强度振荡挑起的最低阶纵向声呼吸声子。我们的研究结果提供了一个广义的理解弗里德尔定律在UED和表明，通过设计的表面法线和原始晶格矢量的错位，相干晶格摆动和有效的剪切应变可以产生在晶体薄膜中的激光脉冲激发，这是很难实现的，可以进一步利用动态调谐和切换材料性能。
The inspection of Friedel's law in ultrafast electron diffraction (UED) is important to gain a comprehensive understanding of material atomic structure and its dynamic response. Here, monoclinic gallium telluride (GaTe), as a low-symmetry, layered crystal in contrast to many other 2D materials, is investigated by mega-electronvolt UED. Strong out-of-phase oscillations of Bragg peak intensities are observed for Friedel pairs, which does not obey Friedel's law. As evidenced by the preserved mirror symmetry and supported by both kinematic and dynamic scattering simulations, the intensity oscillations are provoked by the lowest-order longitudinal acoustic breathing phonon. Our results provide a generalized understanding of Friedel's law in UED and demonstrate that by designed misalignment of surface normal and primitive lattice vectors, coherent lattice wobbling and effective shear strain can be generated in crystal films by laser pulse excitation, which is otherwise hard to achieve and can be further utilized to dynamically tune and switch material properties.