title: Four-fold Raman enhancement of 2D band in twisted bilayer graphene: evidence for a doubly degenerate Dirac band and quantum interference.
abstract: We report the observation of a strong 2D band Raman in twisted bilayer graphene (tBLG) with large rotation angles under 638 nm and 532 nm visible laser excitations. The 2D band Raman intensity increased four-fold as opposed to the two-fold increase observed in single-layer graphene. The same tBLG samples also exhibited rotation-dependent G-line resonances and folded phonons under 364 nm UV laser excitation. We attribute this 2D band Raman enhancement to the constructive interference between two double-resonance Raman pathways, which were enabled by a nearly degenerate Dirac band in the tBLG Moiré superlattices.
authors: Department of Electrical and Computer Engineering, University of Houston, Houston, TX 77204, USA.
authors: Yanan
authors: Y
authors: Wang
authors: Zhihua
authors: Z
authors: Su
authors: Wei
authors: W
authors: Wu
authors: Shu
authors: S
authors: Nie
authors: Xinghua
authors: X
authors: Lu
authors: Haiyan
authors: H
authors: Wang
authors: Kevin
authors: K
authors: McCarty
authors: Shin-shem
authors: SS
authors: Pei
authors: Francisco
authors: F
authors: Robles-Hernandez
authors: Viktor G
authors: VG
authors: Hadjiev
authors: Jiming
authors: J
authors: Bao