Second and third harmonics generation by coherent sub-THz radiation at induced Lifshitz transitions in gapped bilayer graphene.

Using the microscopic nonlinear quantum theory of interaction of strong coherent electromagnetic radiation with a gapped bilayer graphene is developed for high harmonic generation at low-energy photon excitation-induced Lifshitz transitions. 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 in induced Lifshitz transitions by the two linearly polarized coherent electromagnetic waves propagating in opposite directions. The obtained results show that the gapped bilayer graphene can serve as an effective medium for generation of even and odd high harmonics in the sub-THz domain of frequencies.