Abstract
We report a study of the cyclotron resonance (CR) transitions to and from the unusual 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 level. The magnitude of these shifts, and their magnetic field dependence, suggests that an interaction-enhanced energy gap opens in the 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.
- Received 18 September 2009
DOI:https://doi.org/10.1103/PhysRevLett.104.067404
©2010 American Physical Society