Zhang Tao, Gao Chaofeng, Liu Dongdong, Li Zhuolun, Zhang Hao, Zhu Mengqi, Zhang Zhenxiao, Zhao Puqin, Cheng Yingchun, Huang Wei
Key Laboratory of Flexible Electronics & Institute of Advanced Materials, Jiangsu National Synergetic Innovation Center for Advanced Materials, Nanjing Tech University, 30 South Puzhu Road, Nanjing 211816, China.
School of Physical and Mathematical Sciences, Nanjing Tech University, 30 South Puzhu Road, Nanjing 211816, China.
Nano Lett. 2022 Jul 27;22(14):5841-5848. doi: 10.1021/acs.nanolett.2c01599. Epub 2022 Jul 11.
The giant light-matter interaction induced by van Hove singularities (vHSs) of twisted bilayer graphene (tBLG) is responsible for enhanced optical absorption and strong photoresponse. Here, we investigated the evolution of vHSs in tBLG under pressure by using Raman spectroscopy. Pressure not only induces a blue shift of the G/R band but also tunes the intensity of the G/R band. The blue shift of the G/R band is due to the reduction of the in-plane lattice constant, and the variation of the G/R band intensity is due to the vHSs' shift of tBLG. Moreover, the main band in the absorption spectrum of tBLG is attributed to multiple transitions from valence to conduction bands. Because the ratio of R to G band intensity increases under pressure and the origins of R and G bands are different, we claim that pressure enhances intervalley electron scattering. This study paves the way for pressure engineering of vHS and the corresponding photon-electron-phonon interaction in tBLG.
扭曲双层石墨烯（tBLG）的范霍夫奇点（vHSs）所引发的巨大光与物质相互作用，是增强光吸收和强光响应的原因。在此，我们利用拉曼光谱研究了压力作用下tBLG中vHSs的演化。压力不仅会导致G/R带发生蓝移，还会调节G/R带的强度。G/R带的蓝移是由于面内晶格常数减小，而G/R带强度的变化则是由于tBLG的vHSs发生了移动。此外，tBLG吸收光谱中的主带归因于价带向导带的多次跃迁。由于压力作用下R与G带强度之比增加，且R带和G带的起源不同，我们认为压力增强了能谷间电子散射。这项研究为tBLG中vHSs的压力工程以及相应的光子-电子-声子相互作用铺平了道路。
