Beibei Shia, Yingdong Xiaoa, Tianyang Hana, Haotian Chenga, Jincan Zhangb c, Qiao Jianga, Hailin Pengb, Han Zhanga, Xing Zhua, Zheyu Fanga
Abstract:It has been revealed that inversion symmetry breaking in graphene could induce non-trivial Berry curvature, which leads to topologically protected valleytronic applications. Here, we propose an active controllable way of realizing the inversion symmetry breaking of single layer graphene, which is induced by the contrasted AB sub-lattice charge polarization. Our theory model indicates the split of in-plane optical phonons (iTO/iLO) at Γ point is the direct result of inversion symmetry breaking in single layer graphene. Density functional theory calculation was used to quantify the sub-lattice charge polarization and the split of iTO/iLO phonons under the external in-plane electric field, which was further confirmed by Raman spectroscopy. We believe that the method of symmetry manipulation by external in-plane electric field advances fundamental comprehension for the inner mechanism of topological phase transition of graphene.
Carbon, 2020. 163 
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