Contributions of intraband dynamics and interband transitions in the generation of high-frequency harmonics by graphene

Abstract

The advent of high-power pulsed laser sources has made it possible to study nonlinear modes of interaction of electromagnetic radiation with condensed matter. One of the actual direction in this areas is the generation of high-frequency harmonics by graphene. The reason for the appearance of high-frequency harmonics in the secondary radiation induced by an electromagnetic pulse is the nonlinear response of the electron subsystem to an external electric field. This response includes the reaction of conduction band electrons (valence band holes) to the external field and the processes of creation (annihilations) of electron-hole pairs. The reaction of existing charge carriers determines the surface density of the conduction current. The processes of creation and destruction of oppositely charged carriers form the surface density of the polarization current. The observed induced radiation is determined by their sum.
The approach based on the quantum kinetic equation provides the opportunity to study in detail the ultrafast dynamics of the electron subsystem of the material within the framework of the single-particle approximation with a given effective Hamiltonian. Using it, the processes of response to an external electric field were simulated and the role of the conduction current and polarization current in different ranges of the induced emission spectrum were compared. The influence of the relaxation processes of the nonequilibrium population of states and their decoherence was estimated.

Speaker

Anatolii D. Panferov
SGU
Russia

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