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arXiv 2402.11275cond-mat.mtrl-sci
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电子显微镜测量的声子色散中光学声子模的系统性缺省

Systematic Absences of Optical Phonon Modes in Phonon Dispersion Measured by Electron Microscopy

Aowen Li, Paul Zeiger, Zuxian He, Mingquan Xu, Stephen J. Pennycook, Ján Rusz, Wu Zhou

AI总结:

本研究利用扫描透射电子显微镜中的动量分辨振动光谱学,发现单层石墨烯在特定Γ点处光学声子信号系统性缺省,理论分析表明其源于不同基态原子散射波的完全相消干涉,该现象为材料局部振动性质的实验评估提供了新见解。

摘要:

声子色散被广泛用于阐明材料的振动性质。作为一种新兴技术,扫描透射电子显微镜(STEM)中的动量分辨振动光谱学提供了一种无与伦比的方法来探索局部结构上依赖 q 的声子行为。在本研究中,我们使用动量分辨振动光谱学系统地研究了单层石墨烯跨越几个布里渊区(BZs)的声子色散,发现光学声子信号在满足 h+2k=3n(n 表示整数)的指数为 (hk0) 的 Γ 点处消失。理论分析表明,观察到的现象源于来自不同基态原子的散射波的完全相消干涉。这一观察结果得到了金刚石研究的证实,应该是由相同元素对称等价对组成的材料的一般特征。此外,我们的结果强调了多重散射在解释体材料振动信号中的重要性。我们证明了系统性缺省和动态效应(这些以前并未受到太多重视)为材料局部振动性质的实验评估提供了新的见解。

英文摘要:

Phonon dispersion is widely used to elucidate the vibrational properties of materials. As an emerging technique, momentum-resolved vibrational spectroscopy in scanning transmission electron microscopy (STEM) offers an unparalleled approach to explore q-dependent phonon behavior at local structures. In this study, we systematically investigate the phonon dispersion of monolayer graphene across several Brillouin zones (BZs) using momentum-resolved vibrational spectroscopy and find that the optical phonon signals vanish at the Γ points with indices (hk0) satisfying h+2k=3n (n denoted integers). Theoretical analysis reveals that the observed phenomena arise from the complete destructive interference of the scattered waves from different basis atoms. This observation, corroborated by the study of diamond, should be a general characteristic of materials composed of symmetrically equivalent pairs of the same elements. Moreover, our results emphasize the importance of multiple scattering in interpreting the vibrational signals in bulk materials. We demonstrate that the systematic absences and dynamic effects, which have not been much appreciated before, offer new insights into the experimental assessment of local vibrational properties of materials.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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