Magneto-infrared spectroscopy of non-polar epigraphene

We report on the magneto-infrared spectroscopy study of the new generation epigraphene grown on a non-polar facet of SiC [arXiv:1910.03697]. Interband Landau level (LL) transitions are observed and fitted well with 1×10⁶ m/s as Fermi velocity in the massless Dirac fermion model. The transitions remain visible as the magnetic field is down to 0.25 T, indicating that the carrier density is no greater than 3.6×10¹⁰ cm^-2 as expected for charge-neutral non-polar epigraphene. When the samples are grown thicker, LL transition splittings are spotted at high magnetic fields. Failing to explain the splittings with electron-hole asymmetry, we suggest that it could arise from (twist) bilayer epigraphene components and we will discuss it with a numerical twist bilayer graphene model.