title: Landau-level splitting in graphene in high magnetic fields.
abstract: The quantum Hall (QH) effect in two-dimensional electrons and holes in high quality graphene samples is studied in strong magnetic fields up to 45 T. QH plateaus at filling factors nu = 0, +/-1, +/-4 are discovered at magnetic fields B > 20 T, indicating the lifting of the fourfold degeneracy of the previously observed QH states at nu = +/-4(absolute value(n) + 1/2), where n is the Landau-level index. In particular, the presence of the nu = 0, +/-1 QH plateaus indicates that the Landau level at the charge neutral Dirac point splits into four sublevels, lifting sublattice and spin degeneracy. The QH effect at nu = +/-4 is investigated in a tilted magnetic field and can be attributed to lifting of the spin degeneracy of the n = 1 Landau level.
authors.affiliation: Department of Physics and Department of Applied Physics, Columbia University, New York, New York 10027, USA.
authors.forename: Y
authors.initials: Y
authors.lastname: Zhang
authors.forename: Z
authors.initials: Z
authors.lastname: Jiang
authors.forename: J P
authors.initials: JP
authors.lastname: Small
authors.forename: M S
authors.initials: MS
authors.lastname: Purewal
authors.forename: Y-W
authors.initials: YW
authors.lastname: Tan
authors.forename: M
authors.initials: M
authors.lastname: Fazlollahi
authors.forename: J D
authors.initials: JD
authors.lastname: Chudow
authors.forename: J A
authors.initials: JA
authors.lastname: Jaszczak
authors.forename: H L
authors.initials: HL
authors.lastname: Stormer
authors.forename: P
authors.initials: P
authors.lastname: Kim