title: Ultralow-frequency Raman system down to 10 cm(-1) with longpass edge filters and its application to the interface coupling in t(2+2)LGs.
abstract: Ultralow-frequency (ULF) Raman spectroscopy becomes increasingly important in the area of two-dimensional (2D) layered materials; however, such measurement usually requires expensive and nonstandard equipment. Here, the measurement of ULF Raman signal down to 10 cm(-1) has been realized with high throughput by combining a kind of longpass edge filters with a single monochromator, which are verified by the Raman spectrum of L-cystine using three laser excitations. Fine adjustment of the angle of incident laser beam from normal of the longpass edge filters and selection of polarization geometry are demonstrated how to probe ULF Raman signal with high signal-to-noise. Davydov splitting of the shear mode in twisted (2+2) layer graphenes (t(2+2)LG) has been observed by such system in both exfoliated and transferred samples. We provide a direct evidence of twist-angle dependent softening of the shear coupling in t(2+2)LG, while the layer-breathing coupling at twisted interfaces is found to be almost identical to that in bulk graphite. This suggests that the exfoliation and transferring techniques are enough good to make a good 2D heterostructures to demonstrate potential device application. This Raman system will be potentially applied to the research field of ULF Raman spectroscopy.
authors.affiliation: State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China.
authors.forename: M-L
authors.initials: ML
authors.lastname: Lin
authors.affiliation: Key Laboratory of Flexible Electronics (KLOFE) & Institute of Advanced Materials (IAM), Jiangsu National Synergetic Innovation Center for Advanced Materials (SICAM), Nanjing Tech University (NanjingTech), 30 South Puzhu Road, Nanjing 211816, China.
authors.forename: F-R
authors.initials: FR
authors.lastname: Ran
authors.affiliation: State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China.
authors.forename: X-F
authors.initials: XF
authors.lastname: Qiao
authors.affiliation: State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China.
authors.forename: J-B
authors.initials: JB
authors.lastname: Wu
authors.affiliation: State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China.
authors.forename: W
authors.initials: W
authors.lastname: Shi
authors.affiliation: School of Physics, Center for Nanochemistry, Collaborative Innovation Center of Quantum Matter, Peking University, Beijing 100871, China.
authors.forename: Z-H
authors.initials: ZH
authors.lastname: Zhang
authors.affiliation: School of Physics, Center for Nanochemistry, Collaborative Innovation Center of Quantum Matter, Peking University, Beijing 100871, China.
authors.forename: X-Z
authors.initials: XZ
authors.lastname: Xu
authors.affiliation: School of Physics, Center for Nanochemistry, Collaborative Innovation Center of Quantum Matter, Peking University, Beijing 100871, China.
authors.forename: K-H
authors.initials: KH
authors.lastname: Liu
authors.affiliation: Key Laboratory of Flexible Electronics (KLOFE) & Institute of Advanced Materials (IAM), Jiangsu National Synergetic Innovation Center for Advanced Materials (SICAM), Nanjing Tech University (NanjingTech), 30 South Puzhu Road, Nanjing 211816, China.
authors.forename: H
authors.initials: H
authors.lastname: Li
authors.affiliation: State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China.
authors.forename: P-H
authors.initials: PH
authors.lastname: Tan