Electron-Hole Asymmetry and Electron-Electron Interaction in Bilayer Graphene

We report precision measurements of the effective mass $m$* in high-quality bilayer graphene samples using the temperature dependence of Shubnikov-de Haas oscillation. In the measured density range of 0.7x10$^{12}$/cm$^{2}$ $<$ $n$ $<$ 4.1x10$^{12} $/cm$^ {2}$, both the hole mass $m$*$_{\mathrm{h}}$ and the electron mass $m$*$_ {\mathrm{e}}$ increase with increasing $n$, with $m$*$_{\mathrm {h}}$ being roughly 20-30$\%$ larger than $m$*$_{\mathrm{e}}$ at the same density. We compare our results to tight-binding calculations and provide an accurate determination of several hopping parameters. The measured $m$* is substantially suppressed compared to non- interacting values, demonstrating the importance of electron- electron interaction in bilayer graphene.