Spectroscopic Characterization of Gapped Graphene in the Presence of Circularly Polarized Light

We present a description of the energy loss of a charged particle moving parallel to a graphene layer and graphene double layers. Specifically, we compare the stopping power of the plasma oscillations for these two configurations in the absence as well as the presence of circularly polarized light whose frequency and intensity can be varied to yield an energy gap of several hundred $\texttt{meV}$ between the valence and conduction bands. The dressed states of the Dirac electrons by the photons yield collective plasma excitations whose characteristics are qualitatively and quantitatively different from those produced by Dirac fermions in gapless graphene, due in part to the finite effective mass of the dressed electrons. For example, the range of wave numbers for undamped self-sustaining plasmons is increased as the gap is increased, thereby increasing the stopping power of graphene for some range of charged particle velocity when graphene is radiated by circularly polarized light.