Strong magnetophonon resonance induced triple G-mode splitting in graphene on graphite probed by micromagneto Raman spectroscopy

• Main Authors: Dresselhaus, Mildred S., Qiu, Caiyu, Shen, Xiaonan, Cao, Bingchen, Cong, Chunxiao, Saito, Riichiro, Yu, Jingjiang, Yu, Ting
• Other Authors: School of Physical and Mathematical Sciences
• Format: Article
• Language: English
• Published: 2014
• Subjects: DRNTU::Science::Physics
• Online Access: https://hdl.handle.net/10356/101645; http://hdl.handle.net/10220/18736
• Institution: Nanyang Technological University

The resonance between the G-band phonon excitation and Landau level optical transitions in graphene has been systematically studied by micromagneto Raman mapping. In purely decoupled graphene regions on a graphite substrate, eight traces of anticrossing spectral features with G-mode peaks are observed as a function of magnetic fields up to 9 T, and these traces correspond to either symmetric or asymmetric Landau level transitions. Three distinct split peaks of the G mode, named G−, Gi, and G+, are observed at the strong magnetophonon resonance condition corresponding to a magnetic field of ∼4.65 T. These three special modes are attributed to (i) the coupling between the G phonon and the magneto-optical transitions, which is responsible for G+ and G− and can be well described by the two coupled mode model and (ii) the magnetic field-dependent oscillation of the Gi band, which is currently explained by the G band of graphite modified by the interaction with G+ and G−. The pronounced interaction between Dirac fermions and phonons demonstrates a dramatically small Landau level width (∼1.3 meV), which is a signature of the ultrahigh quality graphene obtained on the surface of graphite.