title: Interaction-induced shift of the cyclotron resonance of graphene using infrared spectroscopy.
abstract: We report a study of the cyclotron resonance (CR) transitions to and from the unusual n=0 Landau level (LL) in monolayer graphene. Unexpectedly, we find the CR transition energy exhibits large (up to 10%) and nonmonotonic shifts as a function of the LL filling factor, with the energy being largest at half filling of the n=0 level. The magnitude of these shifts, and their magnetic field dependence, suggests that an interaction-enhanced energy gap opens in the n=0 level at high magnetic fields. Such interaction effects normally have a limited impact on the CR due to Kohn's theorem [W. Kohn, Phys. Rev. 123, 1242 (1961)], which does not apply in graphene as a consequence of the underlying linear band structure.
authors.affiliation: Department of Physics, Columbia University, New York, New York 10027, USA. erikku@caltech.edu
authors.forename: E A
authors.initials: EA
authors.lastname: Henriksen
authors.forename: P
authors.initials: P
authors.lastname: Cadden-Zimansky
authors.forename: Z
authors.initials: Z
authors.lastname: Jiang
authors.forename: Z Q
authors.initials: ZQ
authors.lastname: Li
authors.forename: L-C
authors.initials: LC
authors.lastname: Tung
authors.forename: M E
authors.initials: ME
authors.lastname: Schwartz
authors.forename: M
authors.initials: M
authors.lastname: Takita
authors.forename: Y-J
authors.initials: YJ
authors.lastname: Wang
authors.forename: P
authors.initials: P
authors.lastname: Kim
authors.forename: H L
authors.initials: HL
authors.lastname: Stormer