Electron-electron interaction and electron-hole asymmetry in bilayer graphene
Abstract
We report precision measurements of the effective mass m* in high-quality bilayer graphene using the temperature dependence of the Shubnikov-de Haas oscillations. In the density range of 0.7 x 1012/cm2 < n < 4.1 x 1012 /cm2, both the hole mass m*h and the electron mass m*e increase with increasing density, demonstrating the hyperbolic nature of the bands. The hole mass m*h is approximately 20-30% larger than the electron mass m*e. Tight-binding calculations provide a good description of the electron-hole asymmetry and yield an accurate measure of the inter-layer hopping parameter v4 = 0.063. Both m*h and m*e are substantially suppressed compared to single-particle values, providing clear and unprecedented evidence for the strong renormalization effect of electron-electron interaction in the band structure of bilayer graphene.