Charge Density Wave Phase Transition on the Surface of Electrostatically   Doped Multilayer Graphene
  We demonstrate that charge density wave (CDW) phase transition occurs on the surface of electronically doped multilayer graphene when the Fermi level approaches the M points (also known as van Hove singularities where the density of states diverge) in the Brillouin zone of graphene band structure. The occurrence of such CDW phase transitions are supported by both the electrical transport measurement and optical measurements in electrostatically doped multilayer graphene. The CDW transition is accompanied with the sudden change of graphene channel resistance at T$_m$= 100K, as well as the splitting of Raman G peak (1580 cm$^{-1}$). The splitting of Raman G peak indicats the lifting of in-plane optical phonon branch degeneracy and the non-degenerate phonon branches are correlated to the lattice reconstructions of graphene -- the CDW phase transition. 
Gen Long, Shuigang Xu, Ting Zhang, Zefei Wu, Wing Ki Wong, Tianyi Han,   Jiangxiazi Lin, Yuan Cai and Ning Wang
cond-mat.mes-hall