Magneto-plasmons in graphene in a periodically modulated magnetic field

We present infrared magneto-spectroscopy study of graphene in a periodically modulated magnetic field. Corrugated trenches are first patterned on SiC substrate using e-beam lithography and plasma etching. Multilayer epitaxial graphene is then grown over the trenches, forming a periodic structure. In the presence of an external magnetic field, the perpendicular component of the field is spatially modulated, and the modulation strength can be tuned by varying the trench packing density or the titling angle of the field with respect to the substrate. Experimentally, enhanced absorption and salient deviations from single Lorentzian lineshape are observed, resulting from the periodic modulation. The deviated spectra can be well fitted by two Lorentzians, suggestive of the presence of two active modes. In addition, as the packing density of the trenches increases, the coupling between the corrugated graphene structures becomes stronger, resulting in a broadened spectrum.