Probing symmetry breaking in multilayer epitaxial graphene by circularly polarized magneto-infrared spectrscopy

Symmetry breaking in graphene in high magnetic fields has long been an intriguing problem. Here, we report a magneto-infrared transmission spectroscopy study of multilayer epitaxial graphene with circularly polarized light. A four-fold splitting of the zeroth Landau level is found in high magnetic fields and attributed to the lifting of the valley and spin degeneracies and the electron-hole asymmetry. We extract the magnetic field dependence of the splitting gaps and discuss their possible origins. We also observe a surprising electron-hole asymmetry reversal between the monolayer and bilayer graphene components of multilayer epitaxial graphene and propose a possible interpretation.