近日，南京大学徐伟高教授课题组与中国科学技术大学罗毅教授等人合作，成功利用机械拉曼光谱直接表征了层状材料中的剪切声子。相关研究成果已于2023年3月30日在国际学术期刊《自然—光子学》上发表。
该研究团队利用剪切声子和局域等离子体腔之间的传播特性和机械耦合，成功地实现了通过引入机械-拉曼光谱（MRS）直接表征能量为4 cm-1的基态剪切声子。MRS具有超过108倍增强的全局晶体结构表征能力，并能在环境条件下准确测量亚皮米级位移，具有无热噪声的特点。研究结果证明了MRS检测隐藏界面的传播行为和能力。等离子体的广泛可调性使得MRS技术成为广泛应用的强有力工具，包括全局晶体缺陷检测、机械感应和光的机械调制等领域。
研究人员表示，剪切声子是层状材料中的集体原子层运动，携带了关于机械、热和光电特性的关键信息。具有共向原子层运动的声子分支携带了关于层状晶体和异质结构中全局结构和隐藏界面的独特信息，但由于电子-声子耦合非常有限，因此无法检测到。
附：英文原文
Title: Direct characterization of shear phonons in layered materials by mechano-Raman spectroscopy
Author: Fang, Susu, Duan, Sai, Wang, Xingzhi, Chen, Sijie, Li, Li, Li, Hua, Jiang, Baichuan, Liu, Chuanhui, Wang, Nanyang, Zhang, Lei, Wen, Xinglin, Yao, Yagang, Zhang, Jun, Xie, Daiqian, Luo, Yi, Xu, Weigao
Issue&Volume: 2023-03-30
Abstract: Shear phonons are collective atomic-layer motions in layered materials that carry critical information about mechanical, thermal and optoelectronic properties. Phonon branches with co-directional atomic-layer motions carry unique information about the global structure and hidden interfaces in layered crystals and heterostructures, but they are not detectable due to the very limited electron–phonon coupling. Here we utilize the propagating feature and mechanical coupling between shear phonons and localized plasmonic cavities to successfully realize direct characterization of ground-state shear phonons down to 4cm-1 in energy by introducing mechano-Raman spectroscopy (MRS). MRS has the ability to characterize the global crystal structure with more than 108-fold enhancement and to accurately measure subpicometre displacements under ambient conditions with a thermal-noise-free feature. The propagating behaviour and the capacity of MRS to detect optically hidden interfaces are demonstrated. The broad tunability of plasmons makes the MRS technique a robust tool for extensive applications, including global crystal flaw detection, mechanical sensing and the mechanical modulation of light.
DOI: 10.1038/s41566-023-01181-5
Source: https://www.nature.com/articles/s41566-023-01181-5