Metal-insulator transition in graphene induced by circularly polarized photons

Exact stationary solutions of the electron-photon Dirac equation are obtained to describe the strong interaction between massless Dirac fermions in graphene and circularly polarized photons. It follows from them that this interaction forms bound electron-photon states which should be considered as a kind of charged quasiparticles. The energy spectrum of the quasiparticles is of dielectric type and characterized by an energy gap between the valence and conductivity bands. Therefore the electron-photon interaction results in metal-insulator transition in graphene. The stationary energy gap, induced by photons, and concomitant effects can be observed for graphene exposed to a laser-generated circularly polarized electromagnetic wave.

Figure 1

(Color online) (a) Energy spectrum of quasiparticles in graphene in the presence of circularly polarized irradiation (solid line) and in the absence of one (dashed line); (b) scheme of quasiparticle transitions in graphene irradiated at the frequency ${\omega }_0$.