title: Interface Coupling in Twisted Multilayer Graphene by Resonant Raman Spectroscopy of Layer Breathing Modes.
abstract: Raman spectroscopy is the prime nondestructive characterization tool for graphene and related layered materials. The shear (C) and layer breathing modes (LBMs) are due to relative motions of the planes, either perpendicular or parallel to their normal. This allows one to directly probe the interlayer interactions in multilayer samples. Graphene and other two-dimensional (2d) crystals can be combined to form various hybrids and heterostructures, creating materials on demand with properties determined by the interlayer interaction. This is the case even for a single material, where multilayer stacks with different relative orientations have different optical and electronic properties. In twisted multilayer graphene there is a significant enhancement of the C modes due to resonance with new optically allowed electronic transitions, determined by the relative orientation of the layers. Here we show that this applies also to the LBMs, which can be now directly measured at room temperature. We find that twisting has a small effect on LBMs, quite different from the case of the C modes. This implies that the periodicity mismatch between two twisted layers mostly affects shear interactions. Our work shows that ultralow-frequency Raman spectroscopy is an ideal tool to uncover the interface coupling of 2d hybrids and heterostructures.
authors.affiliation: †State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China.
authors.forename: Jiang-Bin
authors.initials: JB
authors.lastname: Wu
authors.affiliation: ‡Department of Physics, Renmin University of China, Beijing 100872, China.
authors.forename: Zhi-Xin
authors.initials: ZX
authors.lastname: Hu
authors.affiliation: †State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China.
authors.forename: Xin
authors.initials: X
authors.lastname: Zhang
authors.affiliation: †State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China.
authors.forename: Wen-Peng
authors.initials: WP
authors.lastname: Han
authors.affiliation: †State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Lu
authors.affiliation: †State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Shi
authors.affiliation: †State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China.
authors.forename: Xiao-Fen
authors.initials: XF
authors.lastname: Qiao
authors.affiliation: §Cambridge Graphene Centre, University of Cambridge, Cambridge CB3 0FA, U.K.
authors.forename: Mari
authors.initials: M
authors.lastname: Ijiäs
authors.affiliation: §Cambridge Graphene Centre, University of Cambridge, Cambridge CB3 0FA, U.K.
authors.forename: Silvia
authors.initials: S
authors.lastname: Milana
authors.affiliation: ‡Department of Physics, Renmin University of China, Beijing 100872, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Ji
authors.affiliation: §Cambridge Graphene Centre, University of Cambridge, Cambridge CB3 0FA, U.K.
authors.forename: Andrea C
authors.initials: AC
authors.lastname: Ferrari
authors.affiliation: †State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China.
authors.forename: Ping-Heng
authors.initials: PH
authors.lastname: Tan
keywords: Raman spectroscopy; graphene; heterostructures; interface coupling; layer breathing modes; two-dimensional materials