Higher Harmonic Generation of Coherent Sub-THz Radiation at Lifshitz Transition in Gapped Bilayer Graphene

The microscopic quantum theory of nonlinear interaction of strong coherent electromagnetic radiation with gapped bilayer graphene is used for consideration of the high harmonic generation at low-energy photon excitation Lifshitz transition. The Liouville–von Neumann equation for the density matrix is solved numerically at the nonadiabatic multiphoton excitation regime. By numerical solutions, we examine the rates of the second and third harmonics generation at the particle-hole annihilation at Lifshitz transitions in the linearly polarized coherent electromagnetic wave. The obtained results show that the gapped bilayer graphene can serve as an effective medium for the generation of even and odd high harmonics in the sub-THz domain of frequencies.