Cyclotron Resonance near the Charge Neutrality Point of Graphene.

We perform infrared studies of the Landau level (LL) transitions in monolayer graphene in magnetic fields up to B = 18T. We observe both intra-band transitions between neighboring hole/electron LLs, as well as inter-band transitions between hole and electron LLs, all proportional to <RADICAL><RADICAND>B</RADICAND></RADICAL> in energy. The lack of precise scaling between different LL transitions and the unexpectedly large energy shifts as a function of the LL filling factor near the charge neutrality point suggest considerable contributions of many-body effects to the infrared transition energies. [ABSTRACT FROM AUTHOR]