▎ 摘　　要

We have studied the quantum Hall (QH) effect in two-dimensional electrons and holes in high quality graphene samples in strong magnetic fields up to 45 T. A distinctive half-integer QH effect is discovered at high magnetic fields, with QH plateaus appearing at filling factors v = +/- 4(|n| + 1/2), where n is the Landau level (LL) index. This finding is consistent with theoretical predictions. In addition, in the extreme magnetic quantum Emit with magnetic fields up to 45 T, we observe LL splittings in graphene at filling factors v = 0, +/- 1, +/- 4. Further detailed investigation shows that the presence of the v = 0, I QH states indicates the n = 0 LL at the charge neutral Dirac point splits into four sublevels, lifting both the sublattice and the spin degeneracy, while the QH states at v = 4 can be attributed to lifting of the spin degeneracy of the n = +/- 1 LLs.